Biological wastewater treatment (anaerobic-aerobic) technologies for safe discharge of treated slaughterhouse and meat processing wastewater

Science of the Total Environment 686 (2019) 681–708

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Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv

Review

Biological wastewater treatment (anaerobic-aerobic) technologies for safe discharge of treated slaughterhouse and meat processing wastewater Asad Aziz a, Farrukh Basheer b,⁎, Ashish Sengar c, Irfanullah b, Saif Ullah Khan b, Izharul Haq Farooqi b a b c

Department of Civil and Environmental Engineering, University of Auckland, New Zealand Department of Civil Engineering, Zakir Husain College of Engineering and Technology, Aligarh Muslim University, Aligarh 202002, India Department of Civil Engineering, Indian Institute of Technology, New Delhi 110016, India

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• SWW is rich in proteins, fats, lipids, fibres, and carbohydrates. • Anaerobic treatment can be used for production of biogas, and removal of organics. • Intermittent sequencing batch reactor is ideal for slaughterhouse waste treatment. • Aerobic granulation technology can be used to remove N and P in SBRs. • Sequential anaerobic-aerobic treatment can produce biogas and remove C, N and P.

a r t i c l e

i n f o

Article history: Received 16 March 2019 Received in revised form 18 May 2019 Accepted 20 May 2019 Available online 23 May 2019 Editor: Huu Hao Ngo

a b s t r a c t Slaughterhouse industry generates considerable amount of wastewater rich in proteins, lipids, fibres, and carbohydrates. Numerous technologies such as electrocoagulation, membrane separation, advanced oxidation, physico-chemical processes, and biological treatment have been implemented for reducing the concentrations of these compounds. Nevertheless, this review aims to provide extensive information solely on the biological treatment (anaerobic and aerobic) of slaughterhouse wastewater. The advantages of anaerobic treatment are excellent organic matter removal, less sludge production, low energy requirement, execution of higher loading rates, and considerable production of biogas. Aerobic treatment on the other hand is a less sensitive process, possess lower start-up period, and efficient nutrient removal process. Numerous case studies are described to

Abbreviations: ABR, anaerobic baffled reactor; ACR, anaerobic contact reactor; AF, anaerobic filter; AFFR, anaerobic fixed film reactor; AFP, aerated facultative pond; AOB, ammonia oxidizing bacteria; APEDA, Agricultural and Processed Food Products Export Development Authority; ASP, activated sludge process; BOD, biochemical oxygen demand; COD, chemical oxygen demand; CPCB, central pollution control board; CWs, constructed wetlands; DAF, dissolved air flotation; DO, dissolved oxygen; EU, European Union; HRT, hydraulic retention time; ISBR, intermittent sequencing batch reactor; LCFAs, long chain fatty acids; MBR, membrane bioreactor; MBBR, moving bed biofilm reactor; MLSS, mixed liquor suspended solids; MLVSS, mixed liquid volatile suspended solids; N&P, nitrogen and Phosphorous; NOB, nitrite oxidizing bacteria; O&G, Oil and Grease; OLR, organic loading rate; ORP, oxidation reduction potential; RBC, rotating biological contactor; SBOD, soluble biochemical oxygen demand; SBR, sequencing batch reactor; SCOD, soluble chemical oxygen demand; SND, simultaneous nitrification and denitrification; SOUR, specific oxygen uptake rate; SRT, sludge retention time; SVI, sludge volume index; SWW, slaughterhouse wastewater; TA, total alkalinity; TCOD, total chemical oxygen demand; TDS, total dissolved solids; TF, trickling filter; TKN, total kjeldahl nitrogen; TN, total nitrogen; TOC, total organic carbon; TP, total phosphorous; TS, total solids; TSS, total suspended solids; UASB, upflow anaerobic sludge blanket; US EPA, United states environmental protection agency; UV/H2O2, ultraviolet light and hydrogen peroxide; VFAs, volatile fatty acids; VOCs, volatile organic compounds; VS, volatile solids; VSS, volatile suspended solids. ⁎ Corresponding author. E-mail addresses: [email protected] (A. Aziz), [email protected] (F. Basheer).

https://doi.org/10.1016/j.scitotenv.2019.05.295 0048-9697/© 2019 Elsevier B.V. All rights reserved.

682 Keywords: Slaughterhouse wastewater Anaerobic/Aerobic treatment Biogas Intermittent sequencing batch reactor

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

bestow maximum understanding of the wastewater characteristics, kind of treatment employed, and complications involved in managing and treating of slaughterhouse effluent. Additionally, role of microbial community involved in the treatment of slaughterhouse waste is also discussed. Sequential anaerobic and aerobic reactors are also reviewed in order to present their advantages over single bioreactors. Intermittent sequencing batch reactor is a promising technology than other high rate digesters in the removal of carbon, nitrogen, and phosphorous. © 2019 Elsevier B.V. All rights reserved.

Contents 1. 2. 3. 4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current meat production and export in the entire globe . . . . . . . . . . . Slaughterhouse wastewater characteristics and discharge guidelines . . . . . Anaerobic digestion and treatment technology for slaughterhouse wastewater 4.1. Anaerobic ponds . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Anaerobic contact reactor . . . . . . . . . . . . . . . . . . . . . 4.3. Anaerobic filter/Anaerobic fixed film reactor . . . . . . . . . . . . 4.4. Upflow anaerobic sludge blanket reactor . . . . . . . . . . . . . . 4.5. Anaerobic SBR . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Aerobic treatment for slaughterhouse wastewater . . . . . . . . . . . . . 5.1. Aerobic ponds/Lagoons . . . . . . . . . . . . . . . . . . . . . . 5.2. Constructed wetlands . . . . . . . . . . . . . . . . . . . . . . . 5.3. Trickling filters . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4. Activated sludge process . . . . . . . . . . . . . . . . . . . . . 5.5. Rotating biological contactor. . . . . . . . . . . . . . . . . . . . 5.6. Moving bed biofilm reactor (MBBR) . . . . . . . . . . . . . . . . 5.7. Intermittent sequencing batch reactor . . . . . . . . . . . . . . . 6. Sequential anaerobic and aerobic treatment for slaughterhouse wastewater. . 7. Microbial community responsible for slaughterhouse waste treatment . . . . 8. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Over the last few decades of increased population and industrialization have resulted in declined water quality. Effluent wastewater coming from slaughterhouses, food processing units, dairy, brewery, tannery, and pharmaceutical industries are rich in impurities, and can cause detrimental effects on both human beings and aquatic flora and fauna. Particularly the slaughterhouse industry has elevated amount of organic matter, suspended solids, oil and grease, and nutrients (Bustillo-Lecompte and Mehrvar, 2015; Mittal, 2006). Moreover, considerable amount of wastewater is generated from slaughterhouses as a result of slaughtering, meat processing, and cleaning of equipment's. Hence, proper mitigation is required before its final disposal. Discharge in sewers, land application, physico-chemical processes, and biological treatment are the current treatment techniques. Land application and discharge in sewers are not recommended because of their nuisance odour, contamination to aquatic water bodies, and possible emanation of harmful gases (Avery et al., 2005; Mittal, 2006). Additionally, chemical treatment is not a feasible option as the addition of chemicals increases the cost of treatment, and also the difficulty in disposing of chemical sludge makes that process uneconomical and unfavourable. On the other hand, biological treatment (anaerobic and aerobic processes) provides substantial amount of advantages over other treatment systems (discharge in sewers, land application, electrocoagulation, membrane separation, advanced oxidation, and physico-chemical processes) (Oğuz and Oğuz, 1993; De Villiers and Pretorius, 2001; Masse and Massé, 2005; Del Nery et al., 2007). The advantages of using anaerobic treatment are excellent organic matter removal, less production of sludge, low energy requirement, execution of higher loading rates, less nutrients requirement, and considerable production of renewable energy in the form of methane. However, the anaerobic process possesses

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some limitation as well. Longer start up period, higher temperature sensitivity, inability to remove nutrients, and low to moderate effluent quality are the chief drawbacks (Chan et al., 2009). Therefore, to tackle this quandary, both anaerobic and aerobic processes must be employed for the removal of nutrients and organic matter (Del Pozo and Diez, 2005; Bustillo-Lecompte and Mehrvar, 2017a). Moreover, by installing a post aerobic unit can viably reduce the concentration of perilous pollutants. In addition to that, biogas generated in anaerobic processes can be used by the industry in numerous purposes like heating, cooking, and for generating electricity (Coimbra-Araújo et al., 2014; Martins das Neves et al., 2009). All in all, biological processes must be executed as a principal secondary treatment unit in any slaughterhouse or meat processing industry. Hence, the objective of this article is to provide extensive knowledge on biological treatment by imparting information on different anaerobic and aerobic technologies employed over a period of almost three decades in the management of slaughterhouse and meat processing wastewater. Global meat production, slaughterhouse wastewater characteristics, and international discharge regulations have also been reviewed. Furthermore, each treatment technique whether anaerobic or aerobic is presented in such a way that provides excellent understanding of each treatment process, design, functioning, and its proficiency in eliminating the perilous contaminants. Additionally, the role of microbial community involved in the degradation of slaughterhouse waste is comprehensively discussed. 2. Current meat production and export in the entire globe The global meat production in 2017 reached to almost 330 million tonnes in case of bovine, poultry, pig, and ovine. The leading meat producing countries in 2017 were United States, Brazil,

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

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Table 1 World's meat production and export in 2017.

Meat production Meat export

World

China

EU

United States

Brazil

Russia

India

Mexico

Argentina

330.38 32.71

85.81 0.59

47.88 4.98

45.84 7.71

27.07 7.02

9.81 –

7.34 1.73

6.80 –

5.58 0.55

All values in million tonnes.

Russia, Argentina, Mexico, and India. Poultry meat production (120.5 million tonnes) was greatest when compared with other meat productions in that particular year (Food and Agriculture Organization of the United Nations, 2018). Table 1 gives world's meat production and export in the year 2017. In India, meat production has considerably increased over the last few decades. In 2010, India was approximately exporting about 1.45 million tonnes of meat worldwide, and thus was generating about 1500 million US$ as revenue (Central Pollution Control Board of India, 2017). In the present scenario, India's meat production has soared to around 1.73 million tonnes (Food and Agriculture Organization of the United Nations, 2018). According to Agricultural and Processed Food Products Export Development Authority (APEDA), there are almost 1176 slaughterhouses and 75 modern abattoirs in India. Major meat producing states are Andhra Pradesh, Uttar Pradesh, Tamil Nadu, and Maharashtra (Central Pollution Control Board of India, 2017; Rao et al., 2010). 3. Slaughterhouse wastewater characteristics and discharge guidelines Slaughterhouse wastewater (SWW) characteristics generally depend upon various factors such as size of slaughtering facility, kind of animals slaughtered, type of slaughtering involved, quantity of water consumed per animal, and washing of slaughtering equipment's. According to World Bank Group (2007), around 1.62–9 m3 of water is consumed per tonne of cattle carcass, and 1.6–8.3 m3 per tonne of pig carcass. Additionally, water consumption and wastewater composition largely depend upon the type of animal slaughtered. Beef or cattle carcass requires much more water than pig or poultry carcass (Gerbens-Leenes and Mekonnen, 2013). Apart from that, Mekonnen and Hoekstra (2012) illustrated that the type of food manufactured greatly increases the water requirement. For example, animal products such as beef and chicken have comparatively greater water requirement than crop products like cereals and pulses. Furthermore, size and type of plant (slaughtering or rendering or meat processing) will also contribute to the amount and intensity of wastewater generated (Massé and Masse, 2000a). All in all, wastewater generated as a result of slaughtering and processing

units have elevated amount of organic matter, nutrients, pathogens, detergents, and sometimes antibiotics and heavy metals as well (Torkian et al., 2003b; Sirianuntapiboon and Yommee, 2006; Cao and Mehrvar, 2011; Bazrafshan et al., 2012; Carvalho et al., 2013). The aquatic environment can be enormously damaged as a result of discharge of this kind of wastewater. There are several cases of deaths throughout the world due to the presence of excessive amount of pollutants particularly pathogens (Cai and Zhang, 2013; Toze, 1999). Eutrophication is also a cause of concern observed due to the presence of ample amount of nutrients (Sengar et al., 2018a). Slaughterhouse wastewater along with different industrial wastewaters are presented to highlight better understanding of its characteristics (Table 2) (Bustillo-Lecompte and Mehrvar, 2015; Caixeta et al., 2002; Choi et al., 2002; Del Nery et al., 2007, 2016; Del Pozo and Diez, 2005; Demirel et al., 2005; Filali-Meknassi et al., 2005a; Fongsatitkul et al., 2004; He et al., 2005; Johns, 1995; Lemaire et al., 2008a; Manjunath et al., 2000; Martínez et al., 1995a; Nandy and Kaul, 2001; Rajakumar and Meenambal, 2008; Schneider et al., 2011). World leading organisations such as United States Environmental Protection Agency (US EPA), European Union (EU), Central Pollution Control Board (CPCB) of India, People's Republic of China Ministry of Environmental Protection, Environment Canada, and Australia and New Zealand Environment and conservation council have given their effluent discharge standards for SWW (Bustillo-Lecompte and Mehrvar, 2017a; Central Pollution Control Board of India, 2016). Table 3 shows the effluent discharge limits for pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrogen and phosphorous (N&P), oil and grease (O&G), and total suspended solids (TSS) by these governing bodies. The wastewater discharged after proper treatment must comply with these standards in order to safely dispose the effluent. The type of treatment usually depends upon the wastewater characteristics, availability of treatment facility, and effluent discharge standards of that particular country. However, in case of organic rich wastewaters especially slaughterhouse effluent, biological treatment is usually employed over other treatment options such as electrocoagulation, membrane separation, and advanced oxidation (Demirel et al., 2005; Chan et al., 2009).

Table 2 Characteristics of different industrial wastewater. Parameter

SWWa

DWWb

ORWWc

TWWd

PWWe

LWWf

pH COD (mg/l) BOD (mg/l) TN (mg/l) TKN (mg/l) NH4-N (mg/l) TP (mg/l) PO−3 4 (mg/l) TSS (mg/l) O&G (mg/l) VFA (mg/l) Alkalinity (mg/l)

5–7.8 1100–15,000 600–3900 50–840 40–700 20–300 15–200 8–120 220–6400 40–1385 175–797 350–1340

6–11 1150–9200 – – 14–272 – 8–68 – 340–1730 – – 320–970

6.9–10 125–1095 – – – 5–51 – – 9–93 – – –

7–7.2 773–1290 400–490 – 42.7–161 – 9.4–27.9 – – – – –

4.2–4.5 5000–80,000 – 135–1250 – 40–320 30–120 – 900–18,800 – – –

– 6190–78,600 3940–34,600 1530–6500 – – 116–1770 – 1850–29,000 – – –

SWWa - Slaughterhouse wastewater; DWWb - Dairy wastewater; ORWWc - Oil refinery wastewater; TWWd - Textile wastewater; PWWe - Pharmaceutical wastewater; LWWf - Livestock wastewater.

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Table 3 International Effluent discharge standards for SWW. Parameter

US EPA

EU

CPCB

China

Canada

Australia

pH COD (mg/l) BOD (mg/l) TN (mg/l) TP (mg/l) O&G (mg/l) TSS (mg/l)

6–9 – 16–26 4–8 – – 20–30

– 125 25 10–15 1–2 – 35–60

6.5–8.5 250 30 – – 10 50

6–9 100–300 20–100 15–20 0.1–1 – 20–30

6–9 – 5–30 1.25 1.0 – 5–30

5–9 40 5–20 10–20 2 – 5–20

4. Anaerobic digestion and treatment technology for slaughterhouse wastewater

this step (2−3 h). In anaerobic digestion VFAs production and accumulation can cause drop in pH, and ultimately can effect methane production (Kuglarz et al., 2011). Nevertheless, amino acid degradation to ammonia will provide adequate alkalinity for the reactor's stability (Del Nery et al., 2007). VFA/alkalinity ratio is an important factor in determining reactor's performance, and in no case it should be N0.3 (Francioso et al., 2010; Li et al., 2014). Thereafter in the acetogenesis step the VFAs produced are degraded to mainly acetate and hydrogen. The only requisite condition is low hydrogen partial pressure (H2 b 10−4 atm) (Salminen and Rintala, 2002). Butyrate CH3 CH2 CH2 COO− þ 2H2 O→2CH3 COO− þ Hþ þ 2H2 ðΔG◦ ¼ 48:1 kJ=molÞ

ð1Þ

Propionate Anaerobic digestion of organic waste, sludge, and high strength industrial wastewater is a widespread technique in biological treatment. Complex organic compounds are degraded with the help of diverse group of microorganisms (bacteria and archaea) in the absence of oxygen. The degradation rate depends mainly upon different bacteria activity rates (Kondusamy and Kalamdhad, 2014). The end product of one species may be the desired substrate for the other, and hence appropriate conditions must be prevailed inside anaerobic digester to obtain final end product in the form of methane (CH4), carbon dioxide (CO2), ammonium (NH4), water (H2O), and hydrogen sulphide (H2S) (Husain, 1998; Yadvika et al., 2004). The degradation process consists of following four basic consecutive steps, viz. hydrolysis, acidogenesis, acetogenesis, and methanogenesis (Fig. 1) (Demirel and Scherer, 2008; Mao et al., 2015). The first step involved in the degradation of complex compounds is hydrolysis. Here the hydrolytic bacteria excrete the co-enzymes in order to provide the soluble products for other microbial species, and hence the soluble monomer can be easily passed through the acidogenic bacterial cell walls (Appels et al., 2008; Amani et al., 2010). The rate of hydrolysis depends upon factors such as temperature, substrate size, porosity, and their biodegradability, and due to that hydrolysis is considered to be rate limiting step in the entire degradation process (Palatsi et al., 2011). The end products obtained are amino acids, long chain fatty acids (LCFAs), monosaccharide's, alcohols, purines and pyrimidines (El-Mashad et al., 2004). The second step involved after hydrolysis is the acidogenesis step, which involves further degradation of soluble compounds like LCFAs, alcohols, amino acids, and monosaccharide's. Acidogenic bacteria finally degrade them to higher (butyrate, propionate) and smaller organic compounds (acetate), which are known as volatile fatty acids (VFAs) (Li et al., 2019). Additionally, H2, CO2, ammonia, methanol, lactate, ethanol, formate, isovaleric acid, caproic acid, and valeric acid are also produced, and the bacterial growth and conversion rates are maximum for

CH3 CH2 COO– þ 3H2 O→CH3 COO– þ HCO−3 þ Hþ þ 3H2

ðΔG◦ ¼ 76:1 kJ=molÞ

ð2Þ Palmitate CH3 ðCH2 Þ14 COO− þ 14H2 O→8CH3 COO− þ 7Hþ þ 14H2

ðΔG◦ ¼ 345:6 kJ=molÞ

ð3Þ From Eqs. (1), (2), and (3) it can be seen that the value of free energy change (ΔGO) for butyrate, propionate, and LCFAs palmitate reactions are 48.1 kJ/mol, 76.1 kJ/mol, and 345.6 kJ/mol respectively (Wang et al., 1999). It indicates that a negative free energy change is required for hydrogen producing acetogenic bacteria (HPAB) to proceed in the forward direction, and this can be done by maintaining low hydrogen partial pressure within the digester. The partial pressure can be reduced considerably with the help of methanogenic and sulphate reducing bacteria (Appels et al., 2008). Methanogenic species utilize the hydrogen produced by HPAB so promptly that it reduces the partial pressure of hydrogen (H2 b 10−4 atm), and thereby increasing the activity of HPAB. The combined production and uptake of hydrogen by two different bacterial consortiums is known as interspecies hydrogen transfer (Morita et al., 2011). The last step involved in the anaerobic digestion process is methanogenesis. The optimum pH required in this phase is 6.8–7.2 (Mun, 2012). The acetate and hydrogen produced in acetogenesis phase gets converted into methane by two classes of methanogens namely acetate utilizing bacteria (AUB) and hydrogen utilizing bacteria (HUB). AUB are mainly responsible for maximum methane production (72%) (Tchobanoglous et al., 2003). However they usually have lower growth rate as compared to HUB. Thus, it is recommended to provide higher sludge concentrations with longer retention time in anaerobic digesters. Apart from that, higher growth rate of HUB results in providing sufficient hydrogen partial pressure for acetogenic bacteria, and thereby the performance of the reactor can be successively maintained. AUB can be further classified into methanosarcina and methanosaeta. Methanosaeta consumes only acetate for its conversion to CH4, while methanosarcina beside acetate can also utilize H2, CO, CO2, methylamines and methanol as substrates (Mun, 2012). 4.1. Anaerobic ponds

Fig. 1. Steps involved in anaerobic digestion process.

Anaerobic ponds (covered) have been successfully implemented in the waste management of slaughterhouse effluent. They have been effectively used for trapping biogas and removing the nuisance odour from the wastewater (Fig. 2(a)) (Massé and Masse, 2000a). The two main factors that allow the usage of anaerobic pond for high strength wastewater are the availability of land and appropriate weather (Mittal, 2006; Massé and Masse, 2000a). Hence, large anaerobic ponds were constructed exclusively in Australia and United States in the late

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

(a). Schematic diagram of anaerobic pond

(c). Schematic diagram of upflow anaerobic sludge blanket

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(b). Schematic diagram of anaerobic filter

(d). Schematic diagram of anaerobic sequencing batch reactor

Fig. 2. Schematic diagram representing: (a). Anaerobic pond. (b). Anaerobic filter. (c). Upflow anaerobic sludge blanket. (d). Anaerobic sequencing batch reactor.

1980's. The hydraulic retention time (HRT) of a typical anaerobic pond is primarily between 3 and 5 d with a maximum depth of 5 m. According to Dague et al. (1990), covered anaerobic pond was established and operated for a meat processing industry of United States. The pond achieved 90% removal of organic matter, with a concurrent production of 0.51 m3 CH4/kg-organic matter. However, the production of biogas is largely dependent upon organic matter loading. Lower BOD loading results in deprived biogas production and vice versa (Safley and Westerman, 1988). Peña et al. (2000) compared the feasibility of using anaerobic pond over high rate upflow anaerobic sludge blanket (UASB) reactor. The result showed that there was no significant difference between the two anaerobic processes. The COD removal efficiencies were 68% and 66% for anaerobic pond and UASB reactor respectively. However, anaerobic pond is considered to be better than other high rate digesters because it required lesser maintenance and operation cost, lower initial investment, and cheap availability of land (Yacob et al., 2006). Also, the production of biogas largely depends upon temperature (Safley and Westerman, 1992). Hammer and Jacobsen (1970) have declared that the efficacy of anaerobic pond can be greatly affected with the decrease in temperature (b21 °C), and it would be very hard for

an anaerobic pond to revive its efficiency if it collapses in winter (Johns, 1995). A study of moderate temperature (18.2–24.9 °C) in Brazil was conducted by Del Nery et al. (2013) for determining the pond's effectiveness. HRT was varied from 2.2 to 3.8 d, and the organic loading rates were increased from 0.26 to 1.05 kg BOD/m3-d in the entire study. The removal efficiencies obtained were 62%, 42%, and 38% for O&G, COD, and BOD respectively. McCabe et al. (2014) have asserted that the anaerobic pond was capable enough in degrading organic matter and potentially viable in generating 328 m3/d of biogas as well. The only shortcoming associated with that pond was the problematic measurement of the exact amount of biogas generated due to the accumulation of fats/crusts on the surface of the ponds. 4.2. Anaerobic contact reactor Anaerobic contact reactor (ACR) is another type of anaerobic digester which has been used productively in the treatment of slaughterhouse waste. The vital characteristic of the ACR is its exceptional ability to retain anaerobic sludge with the help of recycling and sludge separation techniques. Apart from that, considerable reduction in reactor's

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volume can be achieved by separating the system's HRT and sludge retention time (SRT) (Tchobanoglous et al., 2003). At full scale, Black et al. (1974) exhibited excellent removal in organic matter (90%) and volatile solids (40–70%) when operated at organic loading rates (OLRs) of 0.12–0.28 kg/m3-d. Numerous studies have been performed to check the reactors stability. In one such study, Bohm (1986) has examined the performance of 3 m3 of ACR, and confirmed that the reactor was effectively installed and operated at OLR of 5 kg/−m3-d while treating slaughterhouse wastewater. Kostyshyn et al. (1988) employed an ACR at mesophilic temperature for treating the wastewater coming from United States (US) meat packaging plant. The OLRs (2–3 kg/m3-d) and HRT (1.7–2.5 d) proved to be sufficient enough in removing 75% TSS and 85% COD from the wastewater. Another study in US on the efficiency of ACR was evaluated by Stebor et al. (1990). The reactor exhibited admirable removal in TSS (75%), BOD5 (93%), and COD (84%) from meat processing wastewater. Additionally, biogas was also generated having a methane content of 68–98%. However, due to deprive settling of sludge in ACR, made their usage reluctant in the field of anaerobic digestion. 4.3. Anaerobic filter/Anaerobic fixed film reactor Anaerobic filter (AF) or anaerobic fixed film reactor (AFFR) have been implemented largely in the treatment of high strength wastewater especially in slaughterhouse effluent. They usually achieve higher abstraction efficiency with lower effluent suspended solid concentrations. The wastewater flows either downwards or upwards depending upon the reactor's configuration. The pollutant that is organic in nature gets trapped on the surface of the filter media (stone/plastic media), and is then removed by microorganism attached to that filter (Fig. 2(b)) (Young and Mccarty, 1969). The reactor is mainly suited for the treatment of soluble wastewater, and its performance can be largely inhibited due to clogging of filter media (Bustillo-Lecompte and Mehrvar, 2015; Massé and Masse, 2000b; Mittal, 2006). Moreover, parameters like filter media depth, shape and size, temperature, and HRT are crucial in the design of an AF. Viraraghavan and Varadarajan (1996) reported that HRT and temperature plays a vital role in the treatment of organic compounds. Harrison et al. (1991) exhibited that maximum COD removal of 77% was achieved at 26.7 °C by increasing the HRT to 3.9 d. Another study on the performance of AF treating slaughterhouse wastewater was conducted by Campos et al. (1986) over a period of six years, the reactor achieved 85% COD and 88% suspended solids removal efficiency at OLR of 1.4 kg/m3-d. Apart from that, Andersen and Schmid (1985) and Festino and Aubart (1986) have declared that around 70–85% of organic matter was successfully converted to methane at 2–3 kg/m3-d OLRs. However, higher COD loadings resulted in deprived performance of AF (Tritt, 1992; Johns, 1995). Also, the performance of AF can be further diminished due to the presence of suspended solids and oil and grease. In a case study by Andersen and Schmid (1985), lower performance of pilot scale AF was examined as a result of evaluated concentrations of oil and grease. Therefore, removal of oil and grease is an essential prerequisite in AF. Metzner and Temper (1990) achieved 90% COD reduction as a result of combined primary (drum screen, mud trap and a grease separator) and secondary treatment (AF) in case of German meat processing plant. In order to observe the effect of organic loading rate on the performance of AF, Ruiz et al. (1997) conducted a research in Spain. The loading rates were gradually increased from 0.5 to 6 kg/m3-d over a period of about 90 d. The organic matter removal efficiency was mainly between 60 and 90% at 37 °C in that particular period. However, further increasing the loading rate resulted in declined removal efficiency, but the performance of the reactor was stable up to OLR of 11 kg/m3-d. Higher organic loading rates were also applied by Del Pozo et al. (2000) for evaluating the performance of down flow and up flow

anaerobic fixed film reactors by using PVC corrugated pipes of 70 cm. Both the reactors exhibited 85–95% organic matter removal efficiency at a loading rate of 8 kg/m3-d when operated at 35 °C. Nevertheless, increasing the loading rate to 35 kg/m3-d resulted in decline in removal efficiencies (55%–75%), but the reactors demonstrated a well stabilized behaviour after further increase in OLR (50 kg/m3-d). In India, a study was conducted by Rajakumar and Meenambal (2008) for evaluating the desired HRT and required start up time for an AF treating poultry slaughterhouse wastewater. The HRT was decreased gradually from 36 h to 8 h throughout the research period. That decrease in HRT resulted in increased organic loading rates. At an HRT of 12 h, the reactor successfully removed 79% soluble COD (SCOD) and 70% total COD (TCOD). Nevertheless, the reactor showed lower efficiency of 66% when the HRT was further decreased. Gannoun et al. (2009) treated SWW anaerobically in an AF at 37 °C (mesophilic) and 55 °C (thermophilic). The COD loading rates were increased from 0.9 to 9 kg/m3-d and 0.9 to 6 kg/m3-d for thermophilic and mesophilic respectively. For mesophilic period the maximum organic matter removal efficiency was around 92% at a loading rate of 2.8 kg/m3-d, but further increase in loading rate resulted in decline in removal efficiency (80%). However, the biogas production enhanced considerably by increasing the loading rate to 4.5 kg COD/m3-d. On the other hand, the thermophilic period exhibited 93% COD removal up to 3.6 kg/m3-d of OLR, and b1.4 l/d of biogas was produced at that particular time period. However, on increasing the loading rate to 4.5 kg/m3-d resulted in decreased biogas production and organic matter removal efficiency. A research on the applicability of AF in case of high strength wastewater (cold meat industry) was conducted by León-Becerril et al. (2016). The start-up period was reduced to just 15 d as a result of utilizing the already acclimatized sludge. The AF reactor exhibited excellent removal efficiency in case organic matter with TCOD and BOD removal efficiency of 84% and 88% respectively. The average methane yield of 422 ml CH4/g-COD was obtained when the reactor operated stably (OLR of 1.17–3.5 kg/m3-d) at a temperature of 37 °C.

4.4. Upflow anaerobic sludge blanket reactor In late 1970's, UASB technology was developed by Lettinga and his co-workers in Netherlands as a modification of high rate anaerobic digesters (Tchobanoglous et al., 2003). Over the last three decades, UASB technology has been proven to be proficient enough in the treatment of slaughterhouse wastewater. The wastewater enters from bottom most part of the reactor, and travels within a blanket of sludge in an upward continuous manner. The treated effluent can be acquired from the top most portion of the digester (Fig. 2(c)). Solid (sludge), liquid (wastewater), and gases (CH4 & CO2) are the three main component of upflow anaerobic sludge blanket reactor. Mixing of the sludge is usually carried out by the upflow velocity and biogas. Nevertheless, the size of the sludge particle (flocculent/granular) is also a vital parameter in the performance and operation of an UASB. The particles must also retain back to the bottom of the reactor in order to avoid their escape. Therefore, upflow liquid velocity is a crucial component in the design of an UASB, and it should be increased accordingly with the performance of the reactor (Manjunath et al., 2000; Del Nery et al., 2007, 2008) Several full scale UASB reactors had been successfully established in New Zealand and Belgian in the late 1980s (Steiner, 1987). The functioning of UASB reactors largely depends upon the concentration of the influent organic matter, and the main drawback of treating slaughterhouse wastewater in an UASB reactor is its inability to operate at higher loading rates as a result of presence of suspended and colloidal (cellulose, protein, and fats) impurities. Sayed (1987) were able to provide maximum organic loading rate of 11 kg/m3-d to any UASB reactor (granular sludge) treating slaughterhouse wastewater. Sludge washout is a very common issue especially

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at high loading rates, which generally results in decline in bacterial activity. Ruiz et al. (1997) evaluated the performance of UASB reactor by increasing the organic loading rates from 1 to 6.5 kg COD/m3-d at a constant temperature of 37 °C. The slaughterhouse wastewater was having the following characteristics: COD = 8000 mg/l, TSS = 1200 mg/l, PO−3 4 = 20 mg/l, NH4 = 44 mg/l and pH = 7.2. Maximum COD removal (90%) was observed at 5 kg COD/m3-d. However, further increase in the loading rate resulted in declined removal efficiency (59%). Nevertheless, SCOD and methane generation (60%) were independent from increased loading rates, and were fairly constant throughout the research period. Martínez et al. (1995b) examined the performance of anaerobic reactor receiving high concentrations of fats and suspended solids from an effluent treatment plant (slaughterhouse) of Uruguay. The wastewater was rich in suspended solids, organic and inorganic contents. The primary treatment was ineffective in case of slaughtering (blood) wastewater, but showed positive result in case of tripe processing and pen cleaning wastewater (60% particulate COD removal). The secondary treatment (UASB) removed about 70% particulate COD and 60% fats, but on the other hand was unable to remove SCOD. Considerable removal of fats and solids were achieved by employing a pressurized air in the flotation tank. In Columbia, Hansen and West (1992) conducted a research by taking three different wastewater streams of a slaughterhouse. The three streams were cooker condensate wastewater, raw blood, and wash-up water. In the first phase 98% condensate water and 2% raw blood were used in the anaerobic digester (UASB), while in the second phase 44% condensate water and 56% of wash-up waster were used. The maximum TCOD removal efficiency was 72% and 87% for phase I and II respectively. However, accumulations of volatile fatty acids (VFAs) were observed with increased loading rates, and thus the HRT was increased again to avoid their accumulation. According to Callaghan et al. (2002) and Kuglarz et al. (2011), VFA/ total alkalinity (TA) is an important indicator of the system's performance and stability. The anaerobic digestion can be inhibited largely if that ratio exceeds 0.3 (Hamawand et al., 2015; Kuglarz et al., 2011). VFAs (acetate, propionate, and butyrate) are produced as intermediate products in the process of anaerobic digestion. Their presence in excessive amount can inhibit the process, and can ultimately affect the methanogenic activity of the sludge (Chen et al., 2008). Wong et al. (2007) have conducted two experiments in evaluating the consequence of increasing VFAs and loading rates. In the first experiment mixed VFAs (acetate/butyrate/propionate) having a COD of 20 g/l was used as substrate. The increased loading rates (0.82–10.4 kg COD/m3-d) resulted in increased biogas production (58–82% CH4) with simultaneous removal of COD (83–99%). Thereafter, the mixed VFAs feed was changed to single feed of acetate, propionate, and butyrate each with 20 g COD/ l as substrate. Acetate feed reactor showed some inhibitory effect of pure acetate on biogas production but subsequently recovered after a period of 200 h. The methane produced (90%) from acetate feed was 10% higher than mixed VFAs feed. However, 15% reduction (75%) in COD was observed as a result of change in the feed. In case of butyrate feed reactor around 72–80% of methane was produced as a result of two step degradation of butyrate. Complete inhibition was observed when propionate feed was used as a sole substrate for feeding. Moreover, it has been reported that the inhibition caused by acetate and butyrate are less significant than the inhibition caused by only propionate feed (Callaghan et al., 2002; Rajagopal et al., 2013). Del Nery et al. (2001) have also studied the performance of the VFAs by increasing the upflow velocity and organic loading rates in case of 2 full scale UASB reactors (each 450 m3) treating slaughterhouse wastewater. The reactors received about 2695 mg/l of influent COD at an initial OLR of 0.51 kg COD/m3-d. However, the organic loading rate was increased gradually to 2.11 kg COD/m3-d in a period of 144 d. The result showed that both the reactors were capable enough in removing SCOD from the system with the removal efficiency of 84–94% (R1) and 81–93%

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(R2), and the process was not inhibited at increased VFAs concentrations. Additionally, the performance of anaerobic reactors can be greatly influenced with the conversion of proteins to unionized ammonia and degradation of lipids to long chain fatty acids (LCFAs). Both the factors can affect the reactor's performance, and can ultimately inhibit the biogas production (methane) (Salminen et al., 2001). In order to assess the effect of long chain fatty acids on the performance of UASB reactor (6.67 l) a research was conducted by Hwu et al. (1998) at 35 °C. LCFAs mixtures of stearic acid (15%), palmitic acid (35%), and oleic acid (50%) were used as sorbates (COD), and sludge granules as sorbents from Taipei slaughterhouse, Taiwan. The performance of the digester was evaluated by increasing the concentrations of LCFAs from 0.086 to 0.250 g/g VSS-d, and simultaneously observing the floatation of sludge from the sludge bed in a specific time interval. The reason for collapsing of an UASB reactor was found mainly because of the floatation of the anaerobic sludge, rather than due to the inhibition of methanogenic consortium. Similar results of sludge washout, process inhibition, and flotation of biomass were also observed (Hwu et al., 1998; Rinzema et al., 1993; Silva et al., 2014; Sousa et al., 2009). In another study by Rodríguez-Méndez et al. (2017), inhibitory effects of LCFA's were analysed. The result revealed that hydrolysis step was not affected as a result of LCFAs inhibition as compared to later degradation steps (acetogenesis and methanogenesis). Additionally, palmitic acid concentrations and LCFA/volatile solid (VS) ratios can be used as inhibitory indicators. Complete inhibition was observed as a result of increased palmitic concentrations (N40%) and LCFA/VS ratio (N1.7). Hence, both factors can be used in controlling and preventing LCFAs inhibition in case of anaerobic digester. Several other lab and pilot scale studies using UASB reactors are shown in Table 4. A full scale research on the slaughterhouse wastewater was evaluated in Brazil by Miranda et al. (2005). The entire research was conducted by installing two large scales UASB reactors each having a capacity of 1600 m3 and 800 m3. The first UASB reactor (1600 m3) collapsed after 6 months of operation. Accumulation of O&G on the surface of biomass resulted in declined performance. Hence, another anaerobic digester (800 m3) was established for the treatment of meat processing and slaughterhouse wastewater. However, a pre-treatment (physicochemical) unit was installed before the second digester. The removal efficiencies for both the reactors are shown in Table 5. Though the removal efficiency of the second digester (800 m3) was comparatively lower than the first (1600 m3), but the influent value of COD and O&G were significantly decreased after the installation of a pre-treatment unit. Del Nery et al. (2008) examined a study on the formation of granules in case of poultry slaughterhouse wastewater. Granules formed were diverse in size ranging from 0.1 to 3.5 mm. Moreover, 0.6–1.5 mm size granules were dominant in the anaerobic digester. The entire research was conducted at a full-scale slaughterhouse located in Sorocaba, state of Sao Paulo, Brazil. The wastewater was fed to the anaerobic digester (UASB) of 450 m3 capacity after the preliminary treatment. Three vertical ports were selected from bottom most part of the reactor for sludge analysis. The results obtained were satisfactory for TCOD (65%) and SCOD (85%) removal at an OLR of 1.64 ± 0.37 kg COD/m3-d. Del Nery et al. (2016) on the other hand have asserted that 2.2 kg COD/m3-d OLR resulted in 35% O&G, 71% BOD, and 69% COD removal from a UASB (1260 m3) reactor in case of full-scale plant of Pereiras, Sao Paulo State, Brazil. The main units involved in that plant were dissolved air flotation (DAF), UASB, aerated facultative pond (AFP), and chemical DAF. 4.5. Anaerobic SBR In case of slaughterhouse wastewater sequencing batch reactor is considered to be the best available technology (Mace and MataAlvarez, 2002; Pal et al., 2016). Anaerobic sequencing batch reactor

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Table 4 Numerous lab and pilot scale applications of UASB reactors treating slaughterhouse waste. Temperature Reactor (°C) configuration

Reactor volume (l)

OLR

HRT

CODI (mg/l)

CODR (%)

6.2

1.27–17 kg COD/m3-d 3.5 kg COD/m3-d 4 kg COD/m3-d 2.7–10.8 kg COD/m3-d 13–39 kg SCOD/m3-d 31 kg BOD/m3-d 1.15–3.43 kg COD/m3-d 4–15 kg COD/m3-d 9.27 kg COD/m3-d

4–0.3 d

5100

64–99 3100

10 h 10 h 22–14 h

1100–7250 70 600–3900 – 1100–7250 90 600–3900 – 2000–6000 80–85 1300–2300 95

7–2 h

3143–4288 68–85 914–1917

35

UASBa

30 30 35

a

UASB DAF UASBb UASBa

11.4 11.4 7.2

33

UASBa

1000

25–39 29–35

UASBa HUASBc

3 5.4

19.7–27.31

UASBa

15

29–35

HUASBc

5.4

30

UASBa

33.9

4.5–3.5 h 7333 – 24–8 h 3000–4800 80

BODI (mg/l)

5500 750–1890

BODR TSSR (%) (%)

CH4 (%)

–

57.5–72 0.68–3.99 Borja et al., 1994

–

Biogas (l/d)

References

– – – – 81–86 –

– Manjunath et al., 2000 – Manjunath et al., 2000 10.1–12.6 Caixeta et al., 2002

–

–

–

Torkian et al., 2003b

95 –

– – 60–84 75

– 3.3

–

0.88–0.3 d 10 h

3534–4994 76–90 2646

–

41–55 62–64

20–95

Chávez et al., 2005 Rajakumar and Meenambal, 2008 Nacheva et al., 2011

3000–4800 86

–

93

5.8

Rajakumar et al., 2012

6–36 h

2550–5350 36–84 –

–

43–65 –

–

Saghir and Hajjar, 2018

750–1890

72

CODI - Influent COD; CODR - COD removal; BODI - Influent BOD; BODR - BOD removal; TSSR - TSS removal; UASBa - Upflow anaerobic sludge blanket; DAF UASBb - Dissolved air flotation upflow anaerobic sludge blanket; HUASBc - Hybrid upflow anaerobic sludge blanket.

(ASBR) was invented by Richard R. Dague and his associates at Iowa State University (USA) in 1993 as a modification of anaerobic contact and anaerobic activated sludge processes (Dague, 1993; Sung and Dague, 1995). Feed, react, settle, and decant all takes place sequentially a single batch reactor (Fig. 2(d)). As a result of that, post clarifier requirement is eliminated. ASBR is simple in process and it requires less operating and maintenance cost as compared to other anaerobic digesters (Massé and Masse, 2000b). Moreover, biomass retention is a key phenomenon in ASBR. During feeding, the wastewater enters into a batch reactor having a fixed volume. Thereafter, in the react phase, the biomass and the organic matter gets mixed either continuously or intermittently with the help of mixer for a fixed interval of time. In that phase, organic matter gets converted into biogas (CH4 and CO2) (Steele and Hamilton, 2010). The rate of biogas production depends upon the Food/Mass (F/M) ratio. During starting of the react phase, high F/M ratio is observed with considerable generation of biogas (Ndegwa et al., 2008). However, the rate of biogas production got decreased with time and so does the F/M ratio. Thereafter, in the third (settling) phase, due to lower F/M ratio, supernatant (treated water) gets separated from the biomass. Lower F/M ratio results in enhanced settling of the biomass (Ndegwa et al., 2008). Subsequently to that comes the decanting phase, which results in withdrawn of the treated water from the reactor, and thus the completion of the cycle as well. The next cycle continues in the same manner, and the number of cycles depends upon the system's HRT (Dague, 1993; Wirtz and Dague, 1996). The generation of biogas depends largely upon the rate of mixing in the react phase. Therefore, a study was conducted by Sung and Dague (1995) to evaluate the effect of mixing (continuous or intermittent) in ASBRs. The researchers took 4 different ASBR (A, B, C, and D) which were having different depth to diameter ratios (5.6, 1.83, 0.93, and 0.61). The OLR for reactors A and B were 2, 4, 6, and 8 kg/m3-d at each HRT (48, 24, and 12 h), while for reactors C and D, the loading rates were 2, 4, 6, 8 kg/m3-d at 48 and 24 h, and2, 4, 6, 8, 10, 12 kg/m3-d at

12 h. From that study, it can be concluded that methane production rate (l/h) varied significantly in a course of 6 h with a peak production of 3.5 l/h in case of continuous mixing, whereas for intermittent mixing (5 min/h) the methane peak production was well below 3 l/h. However, the rate of production of methane over a period of 6 h in case of intermittent mixing was higher as compared to the continuous mixing. For COD removal, both type of mixing proved to be efficient and there was no substantial variation. Formation of granules by artificial means was assessed by Wirtz and Dague (1996) by using three different enhancement techniques. Granular activated carbon (GAC), powdered activated carbon (PAC), and cationic polymer were used in three different ASBRs at 35 °C. The fourth reactor was used as a control unit with no chemical addition. The HRT was maintained at 24 h, but the OLRs were increased from 3 to 12 kg/m3-d by increasing the synthetic sucrose concentrations. The cationic polymer enhancement took minimum of 108 d to reach the maximum loading rate of 12 kg/m3-d as compared to other three reactors. Moreover, considerable granulation was observed by using cationic polymer only within a period of 30 d, and after 60 d of stable operation, around 95% removal in COD was observed at an OLR of 6 kg/m3-d. In early 2000, extensive research was conducted by Daniel I Masse and Lucie Masse in case of slaughterhouse effluent. In one such research, Massé et al. (1999) collected the wastewater sample from six different Canadian slaughterhouses. They collected two different types of anaerobic sludge (granular and flocculant) that can be used in 4 anaerobic sequencing batch reactors, each having a volume of 42 l. Reactor 1st and 2nd were fed with the granular sludge, while reactor 3rd and 4th with flocculant one. The ASBRs were operated at 30 °C for varying OLRs (1.1–11.5 kg COD/m3-d), and the results are shown in Table 6. Excellent removal in COD, protein, and TSS were observed at all three loading rates. Apart from that, no accumulation of VFAs were observed, which resulted in considerable production of methane (74%) having a methane yield of 0.54–0.67 l/g VS in the entire research period.

Table 5 Removal efficiencies for two large scales UASB reactor. Reactor

OLR (kg COD/m3-d)

CODI (mg/l)

CODE (mg/l)

Removal (%)

O&GI (mg/l)

O&GE (mg/l)

Removal (%)

UASB (1600 m3) UASB (800 m3)

0.88–1.64 0.86–2.43

2030–3350 988–2774

440–646 104–400

78–80 70–92

413–645 140–460

130–193 27–134

68–70 27–58

CODI - Influent COD; CODE - Effluent COD; O&GI - Influent O&G; O&GE - Effluent O&G.

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Table 6 ASBR's performance with varying COD, protein, and TS concentrations for both granular and flocculant sludge samples. Run

Sludge type

CODI

CODE

Removal (%)

ProteinI

ProteinE

Removal (%)

TSI

TSE

Removal (%)

1

Granular Flocculant Granular Flocculant Granular Flocculant

6908

1511 1450 1842 880 601 365

78 79 81 91 95 97

288

66 78 95 73 33 16

77 73 82 86 94 97

4892

2959 2091 3381 1742 1630 1457

40 57 45 71 77 80

2 3

9665 11,530

530 514

6098 7121

CODI - Influent COD; CODE - Effluent COD; ProteinI - Influent Protein; ProteinE - Effluent Protein; TSI - Influent TS; TSE - Effluent TS.

Another research of Massé et al. (2001), focussing on slaughterhouse wastewater was conducted to evaluate the start-up performance at ambient temperatures (20 °C and 25 °C). The study confirmed that 136 and 168 d were ample enough for starting the ASBR at 20 °C and 25 °C respectively. The OLR was increased swiftly from 0.46 to 2.34 kg/m3-d just within a period of 20 d. As a result of that, decrease in methane production was observed. Therefore, the loading rates were lowered to 1.12 and 1.57 kg/m3-d for 20 °C and 25 °C respectively. Thereafter, the loading rates were increased gradually in order to allow complete degradation of the organic content. Methane production was almost 0.3 l/g-COD at 2.6 kg/m3-d (20 °C) and 3 kg/m3-d (25 °C) respectively. Moreover, above 90% of SCOD and 77% average SS removal were achieved at both the temperatures. The limiting factors observed were the particulate matter hydrolysis at 25 °C and reduction of VFAs and soluble compounds at 20 °C. Massé and Masse (2001) examined the influence of temperature and loading rates by installing 4 ASBRs in case of slaughterhouse wastewater. Each reactor was operated at 30 °C, 25 °C, and 20 °C for 80 d, 137 d and 469 d respectively. At all the operating temperatures and maximum OLRs (4.93, 2.94, 2.75 kg TCOD/m3-d), the TCOD and SCOD removal efficiencies were exceptional (N90%). However, suspended solids concentrations can cause turbulence, and may hinder the settling process as a result of its slow degradation. Nevertheless, around 91%, 80%, and 86% SS were removed at operating temperatures of 30 °C, 25 °C, and 20 °C respectively. Maximum percentage of methane (78%) was observed at 20 °C as compared to 25 °C (76%) and 30 °C (74%). The reason for that behaviour was the increased solubility of H2 and CO2 at lower temperatures. Hence, increase in concentration of methane was observed as a result of their ultimate conversion to methane by hydrogen utilizing bacteria. Similar results of increased methane concentrations were observed by Massé and Croteau (1999) treating swine manure. In order to evaluate the effect of shock load on the performance of ASBRs treating slaughterhouse wastewater, Masse and Massé (2005) applied soluble shock loads at 20 °C. The experiments were conducted in four 42 l ASBRs. Two reactors were operated under varying shock loads, while the other two received normal loading rates (2.60 ± 0.36 kg/m3-d). In soluble shock load, two experiments S1 and S2 were conducted. In S1, two separate shock loads on day 8 (4.22 kg/m3-d) and day 12 (7.93 kg/m3-d) were applied, while in S2, three successive shock loads on day 33 (8.95 kg/m3-d), day 35 (7.55 kg/m3-d), and 37 (9.32 kg/m3-d) were applied to the reactors. In both the experiment increased soluble loading rates resulted in increased effluent SCOD, SS, VFAs (acetic acid, propionic acid, and isovaleric acid), NH4, alkalinity, and pH. On the other hand, a decrease in methane yield was observed with increased loading rates. However, under normal operating conditions (OLR-2.60 ± 0.36 kg/m3-d), all the effluent parameters of shock load reactors were similar to those of control reactors expect for methane yield which was higher in case of shock load reactors. Masse et al. (2001) also evaluated the degradation of fat particles by using NaOH and three different lipases of animal, plant, and bacterial origin by conducting the experiments in 1 l beakers. Slaughterhouse wastewater and distilled water (fats fragments) were mixed in a ratio of 50:50, and were used as a substrate source. The results showed that

animal lipase was very effective in removing fat particle (60%) than any other lipases and NaOH. Temperature plays a crucial role in anaerobic digestion process. Higher temperature results in increased bacterial activity and substrate removal (Dague et al., 1998). Rate of biochemical reaction gets doubled for every 10 °C rise in temperature, but over a constrained temperature range (Barber and Stuckey, 1999; Sawyer et al., 2003). At mesophilic temperature (35 °C), Ruiz et al. (2001) carried out a study on a wastewater coming from a slaughterhouse located in Narbonne (France). The influent wastewater going to ASBR (3.5 l) was of following characteristics: TCOD - 3.5-4.5 g/l, SCOD – 1.5-3 g/l, SS – 0.5-3.5 g/l. The OLR applied after the feeding of the sludge was 0.6 kg COD/m3-d at an HRT of 3.5–4.5 d. The loading rates were applied gradually, and the maximum loading rate (6.1 kg COD/m3-d) was applied at an HRT of 15 h only after the passage of around 90 d. The result showed that the reactor was efficient up to loading rate of 4.5 kg COD/m3-d with the removal efficiency of 86% and 91% for TCOD and SCOD respectively. Bouallagui et al. (2009) studied the effect of mesophilic and thermophilic temperatures on performance of ASBRs treating SWW and fruit and vegetable waste (F&VW). The research was conducted in 6 laboratory scale ASBRs each having an effective volume of 2 l. Three reactors RI, RII, RIII were operated at mesophilic temperature (35 °C), while RIV, RV, and RVI were operated at thermophilic temperature (55 °C). Reactors RI and RIV were fed with SWW, RII and RV with F&VW, and RIII and RVI with SWW F&VW. The reason for co digesting SWW and F&VW was to increase Carbon/Nitrogen ratio (22.5). The results obtained confirmed that the production of biogas was dependent upon system's temperature and HRT. Biogas production at thermophilic temperature (HRT-20 d) was much better than mesophilic temperature at the same HRT. In addition to that, temperature can also incite increased ammonia concentration in anaerobic processes. According to Gallert and Winter (1997), excessive NH3 concentrations can greatly hindered methane production. At elevated temperatures (N50 °C), the production of methane can be inhibited by 50% as a result of ammonia inhibition. On the other hand, with the decrease in temperature increased production in alkalinity was observed as a result of degradation of protein to ammonia, which shortly combines with carbonic acid to form ammonium bicarbonate (Cuetos et al., 2008). All in all, HRT and temperature plays a crucial role in anaerobic digestion processes, and in order to protect the system from overloading and failure the HRT should be changed according to the temperature or vice versa. Effect of varying HRT (16, 12, and 8 h) on the performance of ASBR was also examined by Myra et al. (2015). The experiment was conducted at laboratory scale in an effective volume of 10 l ASBR at 27–32 °C. Maximum COD removal was observed at 16 h HRT (97%) having an average effluent value 83 mg/l. This value was in compliance with the effluent discharge standard of Philippines (100 mg/l), while the concentrations obtained at other HRTs (12 and 8 h) failed to compliance with the standard value. At 16 h HRT, biogas production was 2.7 l/d having a methane content of 61%. TSS removal was not affected by the change in HRT and the effluent value was well below 70 mg/l of prescribed standard.

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Handous et al. (2017) recently carried a research for improving the biogas generation in ASBR by co-digesting the effluent wastewater (WW) and solid waste (SW) of a Tunisian slaughterhouse. Five ASBRs (R1, R2, R3, R4, and R5) with 1 l capacity were selected for the experimental work. Production of biogas (l/day) at all the loading rates for R1, R2, R3, R4, and R5 were 0.43–1.76, 0.38–1.61, 0.4–1.21, 0.51–1.74, and 0.35–0.73 respectively. The result confirmed that the production of biogas was improved in R4 which was pre-treated with bacterial flora, even though the mixture used in R4 was same as that of R3. Furthermore, around 125,500€/year of net profit can be obtained by pretreating the waste before an anaerobic process. Numerous other high rate digesters such as anaerobic fluidised bed reactor, anaerobic baffled reactor, anaerobic membrane bioreactor, expanded granular sludge bed reactor, continuously stirred tank reactor, and static granular bed reactors have been implemented in the treatment of slaughterhouse waste. Table 7 shows the case studies of such reactors that have been used mainly in the treatment of slaughterhouse effluent over the past few decades. 5. Aerobic treatment for slaughterhouse wastewater Aerobic digestion takes place in the presence of oxygen with the help of mixed culture of heterotrophic and autotrophic microorganisms.

Heterotrophic microbes utilize organic compounds as their carbon source, while autotrophic microbes consume inorganic carbon such as CO2. The mixed aerobic consortium degrades the organic matter and ammonia into less harmful compounds like CO2, H2O, nitrite (NO−2), and nitrate (NO−3), and with considerable production of new cells. Generally, oxidation with synthesis and endogenous respiration are the two main steps in aerobic degradation. Due to increased oxygen demand and treatment time requirement, aerobic processes are mainly installed after anaerobic processes (Al-Mutairi, 2009; Bustillo-Lecompte and Mehrvar, 2017a). The process is feasible to be applied to low strength wastewater (COD b1000 mg/l) (Chan et al., 2009). The system is very efficient in eliminating pathogens and awful odours from the wastewater as well. (Arvanitoyannis and Ladas, 2008; Skjelhaugen and Donantoni, 1998). Excess biomass production, daily maintenance, and increased oxygen demand are the main drawbacks. Additionally, biological sludge must be treated before its final disposal. Nevertheless, excellent organic matter and nutrients (N&P) removal can be achieved by this method (Bustillo-Lecompte and Mehrvar, 2015; Chernicharo, 2006). Conventional biological nitrogen removal is achieved by nitrification and denitrification, while phosphorous removal is accomplished by enhanced biological phosphorous removal (EBPR) in anaerobic and aerobic cycles (Zeng et al., 2004).

Table 7 Implementation of high rate anaerobic digester's in slaughterhouse industry. Temperature Waste (°C)

Reactor

HRT

Influent COD (mg/l)

TCOD (%)

–

2500–5000

8h

340–680

5–0.5 d

7500–30,000 30–85 –

26–2.5 h

490–730

–

4700–28,700 –

8–0.5 h

250–4500

75–99 –

20 h

4000

–

83–97 –

45–18 d

–

–

–

19–5.2 h

1440–4200

47–91 –

–

1.2 d

5800–20,150 97

–

–

67–70 Nachaiyasit and Stuckey, 1997 – Salminen and Rintala, 1999 – Núñez and Martínez, 1999 – Fuchs et al., 2003

16–100 h

2000–15,000 81–94 –

–

–

3.33–1.25 d 50–25 d

5440–15,500 –

62–97 –

–

–

–

–

Saddoud and Sayadi, 2007 77–79 64–66 Cuetos et al., 2008

50–25 d

–

–

–

81–83 59–65 Cuetos et al., 2008

60–36 h

4200–9100

85–98 –

–

–

24–4 h

760–4200

64–95 –

–

–

30 d

–

–

–

–

– 31–10 d 2d

8450–41,900 18–57 – 40,500 57–77 – 5919–10,604 95 –

– – –

31–67 Fantozzi and Buratti, 2009 – Marcos et al., 2010 74 Marcos et al., 2012 70 Jensen et al., 2015

–

13,500

32–69 –

–

–

35

SMWWa Fluidised bed reactor

2

35

SWWb

Fluidised bed reactor

0.5

–

SWWb

Fixed bed reactor

4.58

b

25–35

SWW

Baffled reactor

5.16

35

SWWb

Down flow fixed bed reactor

1

35

SWWb

Fluidised bed reactor

1

Baffled reactor

10

15–35

a

SMWW c

35

SFW

Continuously stirred tank reactor

3

35

SWWb

2.7

30

SWWb

Expanded granular sludge bed reactor Membrane bioreactor

33–39

d

FWW

Membrane bioreactor

400

37

SWWb

Membrane bioreactor

50

34

SSWe

34

7

Completely mixed stirred digester

3

f

Completely mixed stirred digester

3

b

SMW

22

SWW

Static granular bed reactor

–

30–35

SWWb

Anaerobic hybrid reactor

1.77

36

PLg

Continuously stirred tank reactor

17

b

38 37 37

SWW SWh SWWb

Anaerobic digester Continuously stirred tank reactor Membrane bioreactor

2 6.2 200

26

SWWb

Acidogenic reactor (AR) methanogenic reactor (MR)

AR = 40 MR = 87

1.8–9.5 kg COD/m3-d 0–12 kg SCOD/m3-d 2–18.5 kg COD/m3-d 0.67–4.73 kg COD/m3-d 2.5–25 kg COD/m3-d 2.9–54 kg COD/m3-d – 1–4.6 kg VS/m3-d 2.1–15.8 kg COD/m3-d 6–8 kg COD/m3-d 2–4.5 kg COD/m3-d 4.37–13.27 kg COD/m3-d 0.9–1.7 kg VS/m3-d 1.85–3.7 kg VS/m3-d 0.64–4.97 kg COD/m3-d 0.76–20.24 kg COD/m3-d – 0.5–4.5 g COD – 3–3.5 kg COD/m3-d 0.4–0.7 kg COD/m3-d

SCOD (%)

References

Volume Loading rates (l)

VS (%)

CH4 (%)

71–76 –

–

–

–

55–78 Stephenson and Lester, 1986 – Toldrá et al., 1987

–

70

75

71–90 80–94 – 98–50 – –

68%

Tritt, 1992

69–73 Polprasert et al., 1992 58 Borja et al., 1995a 59–78 Borja et al., 1995b

He et al., 2005

Debik and Coskun, 2009 Farooqi et al., 2009

Wang et al., 2018

SMWWa - Synthetic meat wastewater; SWWb - Slaughterhouse wastewater; SFWc - Slaughterhouse food waste; FWWd - Food factory wastewater; SSWe - Slaughterhouse solid waste; SMWf - Slaughterhouse municipal waste; PLg - Poultry litter; SWh - Slaughterhouse waste.

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Nitrification is the oxidation of inorganic nitrogen (NH3/NH4) to nitrite (NO−2) and then to nitrate (NO−3) by autotrophic microorganisms (ammonia oxidizing and nitrite oxidizing bacteria) under aerobic conditions. Thereafter, NO−3 under anoxic conditions get transformed into nitrogen gas (N2) with intermediate compounds as NO−2, N2O, and NO by heterotrophic microorganisms (denitrifying bacteria) (Pan et al., 2013). Nitrification requires oxygen demand, while denitrification sometimes necessitate additional carbon source. Thus, recent studies have conducted to make the process more economical and feasible. Novel processes such as nitritation-denitrification, nitritation-denitritation, nitritation-anammox have been performed recently (Winkler and Straka, 2019). Each process has its own limitations and advantages. In nitritation and denitrification process, partial nitirifation of NH3 to NO−2 is carried out under limited oxygen supply. The process can reduce the aeration cost by 25% as compared to conventional nitrification (Peng and Zhu, 2006). Moreover, the technique can be further enhanced by directly converting the NO−2 into N2 gas by denitrifying polyphosphate accumulating organisms (DPAOs). The process can save additional carbon source as DPAOs can denitrify in the absence of additional carbon. The so-called process is known as nitritation-denitritation. The most recent technique for nitrogen removal is Nitrititation-anammox process. Here ammonia oxidizing bacteria converts half of ammonia into nitrite, and then anammox uses that nitrite as an electron acceptor for converting rest of ammonia into nitrogen gas. It possesses advantages such as complete ammonia removal, less oxygen demand (60%), no carbon source requirement, and less sludge production (75%) (Winkler and Straka, 2019). Biological phosphorous removal is also dependent upon cyclic anaerobic and aerobic conditions. Polyphosphate accumulating microorganisms (PAOs) utilize organic matter like VFAs and store them as poly-hydroxyalkalanoate (PHA)/poly-hydroxybutyrate (PHB) in anaerobic conditions. The energy required for metabolizing comes from breaking their polyphosphate bonds, and thus they release excessive orthophosphate. In limited organic carbon PAOs compete with denitrifying microorganisms. Subsequently in aerobic conditions PAOs utilizes stored PHA/PHB for growth and synthesis resulting in orthophosphate uptake. Orthophosphate uptake is greater than its release, and thus they are removed from the system by withdrawing certain amount of sludge (Pan et al., 2013; Tanwar et al., 2007). Phosphate uptake is also possible by DPAOs under anoxic condition in the presence of NO−3/NO−2 (Monclús et al., 2010; Sengar et al., 2018a). Additional to that aerobic granulation is also a latest technique for simultaneous removal of nutrients. Hence, employing biological treatment with varying anoxic and aerobic cycles can further reduce organic matter and nutrients concentrations. The aerobic case studies are thus reviewed to better present their feasibility in the removal of organic and inorganic content from slaughterhouse wastewater. 5.1. Aerobic ponds/Lagoons The most common aerobic treatment process used in the treatment of SWW is aerobic ponds/lagoons. The sole difference between ponds and lagoons is the type of aeration provided. Artificial aeration is provided in lagoons, while photosynthesis process provides considerable amount of oxygen in aerobic ponds. Maximum organic matter removal (90–95%) can be observed from aerobic ponds/lagoons. However, due to improper settling elevated concentrations of suspended solids can be observed from these systems. Additionally, treatment time and oxygen requirement largely depends upon influent wastewater characteristics (Mittal, 2006). In treating slaughterhouse wastewater, ponds and lagoons have been usually employed after suitable anaerobic treatment. Hence, limited studies are available in treating raw slaughterhouse wastewater by these processes. A 1000 m3 aerobic lagoon was monitored by Belanger et al. (1986) in the treatment of slaughterhouse wastewater. Influent BOD concentrations varied between 1500 and

691

3000 mg/l. Oxygen was transmitted by 24 submerged emitters at a rate of 850 l of O2/min. The lagoon effectively removed the organic content at an average HRT of 11 d, and the effluent concentrations of BOD were mostly below 50 mg/l. Apart from that, sludge generation was observed to be a prominent issue, and thus trained technicians were employed for that. Apart from that, Evans et al. (2005) evaluated the performance of pilot scale high rate algal ponds on varying nitrogen loading rates. The results showed that deeper ponds were much better in removing ammonia as compared to shallow ponds. Moreover, excellent denitrification efficiency (95%) was also observed when the slaughterhouse wastewater was passed through a series of 3 ponds. Intermediate pond acted as anaerobic/anoxic unit. Evaporative ponds have also been used in treating slaughterhouse waste like hide curing wastewaters. Evaporite salts are formed in such ponds, and in few instances, increased concentrations of hazardous metals were also observed (Tanji et al., 1992). Overall, aerobic ponds are best suited as a post treatment unit where land availability and environmental conditions are appropriate. 5.2. Constructed wetlands Constructed wetlands (CWs) are those systems that involve the use of soil, wetland vegetation, microbial groups and all other natural processes to treat domestic and industrial wastewaters. Constructed wetlands are specifically implemented to treat wastewaters after primary and secondary treatment units (Vymazal, 2014). They are comparatively economical than other treatment options because of their simpler design, lower operation and maintaining cost, and their harmless effects on the environment (Chan et al., 2009; Oller et al., 2011). Constructed wetlands are divided into subsurface flow and surface flow wetlands. Moreover, depending upon the direction of flow they are further classified as vertical and horizontal flow wetlands. Subsurface wetlands due to the presence of gravel, sand, and stones achieve higher pollutant removal efficiencies as compared to surface flow wetlands (Odong et al., 2015). Apart from that, their bottom stratum and slid slopes are covered with a help of polyethylene plastic cover, which prevents the wastewater to get percolated into lower water table. First full scale application of wetland was done in late 1960's (Vymazal, 2014). Application of wetland system started with municipal wastewater, but now wetlands are used to treat industrial, agricultural and leachate waste water as well (Vymazal, 2011). Russell et al. (1994) evaluated the feasibility of surface flow wetlands for the removal of nitrogenous compounds especially nitrate. The denitrifying activity was prevailed inside the surface of decaying plant material. The result showed that proper contact between decaying material and wastewater can further enhance the denitrification rate. Van Oostrom (1995) also examined the feasibility of constructed wetland in treating nitrified slaughterhouse wastewater. Denitrification accounted for 87% nitrogen removal, while remaining 13% through plants and sediments assimilation. Performance of full scale wetland system for treating slaughterhouse wastewater was evaluated in Mexico (Gutiérrez-Sarabia et al., 2004). Sedimentation tank, anaerobic lagoon and constructed wetland were placed in series in the treatment unit. Overall removal efficiencies achieved were 91% (BOD5), 89% (COD) and 85% (TSS). However, only 30% organic matter reduction was achieved in wetland system, which was having 12 mm gravel size. On the other hand, certain pathogens were also removed by the presence of Phragmites australis and Typha latifolia plants. Excellent pollutant removal efficiency was achieved by Struseviciene and Strusevicius (2006) in two stage horizontal constructed wetlands while treating wastewater from a slaughterhouse industry. Primary treatment removed considerable amount of impurities from the wastewater, while secondary biological treatment (constructed wetlands) provided the effluent that can be easily discharged.

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To evaluate the performance of vertical flow constructed wetlands and membrane bioreactor (MBR) a study was conducted by Scholz (2006). Animal rendering wastewater was effectively treated in both the cases after a pre-treatment (DAF). Wetlands proved to be as effective as membrane bioreactors, and the effluent COD and ammonia obtained in case wetland were 167 mg/l and 63 mg/l respectively. Soroko (2007) conducted two experiments to evaluate the removal efficiencies of wetlands while treating slaughterhouse wastewater. In the first experiment, combination of two vertical flows and one horizontal flow constructed wetlands were used, while in second experiment single vertical flow and horizontal flow wetlands were employed. Nitrogen removal efficiency obtained were 78% and 97% from first and second experiment respectively. Additionally, it was reported in a study by Gasiunas et al. (2005), that efficiency of organic pollutant and nutrient removal depends on loading rates. Furthermore, physical and chemical characteristics of the sand medium influence the phosphorus removal. Average efficiency of total nitrogen removal obtained from that study was between 37 and 44%. To study the effect of temperature on wetlands a study was conducted by Carreau et al. (2012) in Canada. The surface flow wetlands were planted with Typha latifolia plants to treat the slaughterhouse effluent. Active volume taken was 89% with hydraulic retention time of 111 d. The results acquired from the system encouraged the implementation of wetlands in colder climates as well. The removal efficiencies reported were quite high for both organic and inorganic contents. About 95% BOD, 72% TSS, 88% total phosphorous (TP), and 87% total kjeldahl nitrogen (TKN) removal was achieved from constructed wetlands in a span of two years. Two consecutive oxidation ponds were used to treat high strength hog slaughterhouse wastewater (Poommai et al., 2015). Ponds were found insufficient to meet the desired effluent standards. Vertical flow constructed wetland was used in addition and the effluent quality was found to be little improved. However, the overall treatment scheme was insufficient to meet the standards due to high strength of wastewater comprising of grease, hairs, solids, and blood. Odong et al. (2015) have used a horizontal subsurface flow constructed system to treat the wastewater by planting each Cyperus papyrus plant in 1m2 area. The horizontal wetland was fed with slaughterhouse wastewater after pre-treating it with anaerobic and aerobic sequencing batch reactors (SBRs). At an HRT of 1.16 d, the COD, total nitrogen (TN), TP, and turbidity removal efficiency obtained were 60%, 46%, 63%, 76% respectively. Apart from that, 100% faecal coliform removal was observed from horizontal subsurface wetland system as well. The authors strongly emphasized the implementation of constructed wetlands as a tertiary treatment unit in case of slaughterhouse effluent.

5.3. Trickling filters Trickling filter (TF) is one of the fixed bed reactors in which different media of high permeability is used for microorganism's growth. Media can be a rock or plastic of varying surface area. Generally, to achieve higher loading rates and to prevent blockage, a media with high surface area is employed. A slim layer comprising of microorganisms is then developed on that surface media. Distribution system is used to allow wastewater to enter into bioreactor, where the wastewater is then trickled over the media surface (Daigger and Boltz, 2011). Bacterial biomass present on the media degrades the organic content in the presence of oxygen. However, due to increased thickness of slim layer results in insufficient oxygen transfer, and thus sloughing of bacterial biomass can then be observed from media surface. Advantages of trickling filter are low operational cost, minimal space and power requirement, and near to ground cost requirement (Johns, 1995). In spite of numerous advantages its application as a secondary treatment unit in the treatment of slaughterhouse effluent is limited, especially in countries like US and Australia.

Phillips (1975) reported the implementation of one high rate trickling filter followed by two sequential biofilters. Moreover, primary treatment (flocculation and sedimentation) was also provided to reduce the loading rate on trickling filters. The results showed that under controlled conditions around 95% BOD removal can be achieved. Clogging of filter media occurs due to high concentration of proteinaceous compounds, which results in declined reactor's performance (Azad, 1976). However, with suitable pre-treatment and plastic media usage, considerable reduction in organic matter can be observed. According to Moodie and Greenfield (1978), about 50% suspended COD discharged from Brisbane slaughterhouse facility was treated by employing a preliminary treatment. A pilot plant comprised of primary (DAF) and secondary treatment unit (two stage trickling filters) was set up by Li et al. (1984). Each trickling filter was 2.4 m high and consisted of media (surface area98 m2/m3). Around 40–50% oil and grease removal were achieved from DAF system. In case of trickling filters organic matter removal efficiencies were 70–85%. Apart from that, nitrification also resulted, but the process was entirely dependent upon loading rates. Intensive studies by Banks and Wang (2004) have shown that loading rates plays a vital role in biological treatment. Intensive studies conducted by them have shown that the organic matter removal efficiencies were 60–85% when operated at OLRs of 1.2–8.1 kg BOD/ m3-d for nine trickling filters. 5.4. Activated sludge process In early 1900s, activated sludge process (ASP) was developed by Ardern and Lockett, and up till now it is one of the most common wastewater treatment technologies due to its simplicity and low cost treatment techniques (Zhao et al., 2018). Treatment of wastewater takes place inside a bioreactor (aeration tank), in which oxygen is provided for degrading the organic content with the help of aerobic microorganisms (Fig. 3(a)). Contaminants are adsorbed on the surface of biomass, and thus get oxidized in the presence of oxygen. This process of adsorption is an integral step in the biodegradation process of organic content (Seyhi et al., 2011). Thereafter, the treated effluent along with sludge (activated sludge solids) enters into clarifier for its further separation. A certain amount of mixed liquor suspended solids (MLSS) is required inside bioreactor for maintaining a desirable F/M ratio. Hence, the settled sludge in the clarifier is recycled back to the aeration tank for maintaining the required ratio and MLSS concentrations. And finally, the treated water can be collected from clarifier's effluent. In early 1980s, implementation of ASP in the treatment of slaughterhouse waste was soared tremendously, and numerous ASP plants were installed worldwide in order to remove both organic and inorganic content. However, in some cases due to the presence of fats in slaughterhouse effluent poor settling of the activated sludge have been reported widely (Hopwood, 1977). Additionally, dissolved oxygen (DO) is another factor that plays a crucial role in degrading fat content. 90% removal in fat content was observed when DO was increased up to 4 mg/l, whereas about 60% removal was obtained when the value of DO was reduced to b0.5 mg/l (Travers and Lovett, 1984). Nevertheless, under similar DO (lower) concentration but with lower fat content no such issue of sludge bulking was perceived (Johns, 1995). Apart from that, attached growth systems are more vulnerable to fat content than suspended growth systems (Heddle, 1979). Heddle (1979) conducted a study to evaluate the performance of ASP by varying F/M ratios. It was done to observe the COD, nitrogen, phosphorus, oil and grease, and suspended solids removal efficiencies. Moreover, production of biomass and consumption of oxygen were the foremost objectives of that research. Lower F/M (0.2–0.4) proved beneficial as compared to higher F/M ratios (1.8–2.0) in removing COD (96%), TSS (95%), TKN (96%), phosphorus (47%), and O&G (94%). Additionally, much less oxygen was utilized with concurrent production of biomass, which was rich in protein (55%). Gariépy et al. (1989) on the

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693

(a). Schematic diagram of activated sludge process

(b). Schematic diagram of rotating biological contactor

(c). Schematic diagram of moving bed biofilm reactor

(d). Schematic diagram of intermittent sequencing batch reactor Fig. 3. Schematic diagram representing: (a). Activated sludge process. (b). Rotating biological contactor. (c). Moving bed biofilm reactor. (d). Intermittent sequencing batch reactor.

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other hand, obtained maximum protein content (78%) while treating slaughterhouse waste. Continuous and intermittent feeding strategy was examined by Lovett et al. (1984) in 4 laboratory scale reactors. An aeration tank of 9 l and settling tank of 1 l was separated by an adjustable baffle. Three reactors were operated continuously with slaughterhouse wastewater, while the single reactor was fed intermittently with wastewater (8 h) and tap water (16 h). The SRT was fixed to 5, 10, and 20 d for the three reactors and 10 d for the last intermittent reactor by maintaining mixed liquor volatile suspended solids (MLVSS) concentrations. The intermittent ASP was comparatively better in removing the impurities from the wastewater. The COD, TKN, and phosphorous removal efficiencies were 98%, 96%, and 96% respectively for intermittent ASP, and 94%, 95%, and 60% respectively for continuous ASP at 10 d SRT. ASP's have also been installed in the treatment of waste generated from pig slurries. In Italy a pilot plant study was conducted by Bortone and Piccinini (1991) for the treatment of waste generated from pig farms. A post aerobic ASP was employed after an anaerobic baffled reactor (ABR) for the desired treatment. The COD and TKN removal efficiencies were 82% and 92% respectively. Additionally, another research on the treatment of pig slurry but at full scale was carried by Bicudo and Svoboda (1995) in Portugal in mid-1990s. Four different aeration strategies (19.5 h, 16.5 h, 14.5 h, and 12 h) were adopted in a modified activated sludge process i.e., extended aeration system. 12 h intermittent aeration showed enhanced SCOD and soluble BOD(SBOD) removal efficiencies of 85% and 98% respectively. As slaughterhouse waste contains high fraction ammonia due to the degradation of proteinaceous compounds, it must be treated before its discharge. Campos et al. (1999) gradually increased the ammonia loading rates from 0.5 to 7.7 kg NH4/m3-d at lab scale in order to observe ASP performance. The findings confirmed the implementation of ASP in removing nitrogenous compounds from the wastewater at large scale, and about 97–99% of ammonia was effectively transformed to nitrate by using a conventional ASP. O'Flynn (1999) too observed the removal efficiencies of organic matter and inorganic impurities by installing a pilot plant and comparing the results with a mathematical model. The maximum COD, ammonia, and phosphorous removal efficiencies were 98%, 99%, and 65% respectively. Using a chemical treatment with biological treatment (activated sludge) has enhanced the level of treatment for abattoir wastewater as reported in a study by Bohdziewicz et al. (2002). Aeration period of 10.5 h resulted in optimum treatment, giving COD removal efficiency of 91.5% and nitrogen removal by 59%. Efficiencies were reported to be dropped using aeration period less than or N10.5 h. Coagulant was added simultaneously to achieve phosphorus precipitation. In order to eradicate the issue of sludge bulking an improvement in the existing ASP was done by incorporating different arrangements in step feeding, tapered aeration, increased volume of aeration tank, and especially by employing an aerobic selector. As a result of that, substantial increase in settling was observed, which enhanced the effluent quality (Al-Mutairi, 2009). Removal of certain drugs such as enrofloxacin and tetracycline from slaughterhouse wastewater by using activated sludge was evaluated by

Carvalho et al. (2013). These pharmaceuticals were significantly removed through sorption to sludge and to organic content of wastewater in batch reactors. Study showed 68% removal of enrofloxacin and 72% of tetracycline from the wastewater. Slaughterhouse wastewater was also treated by using different sequential setup consisting of ABR, ASP system and UV/H2O2 photo reactor at lab scale by (Bustillo-Lecompte et al., 2014). The results illustrated that ABR ASP UV/H2O2 combination provided excellent total organic carbon (TOC) removal (92.5%) at reasonable cost. Table 8 illustrates the implementation of ASP's in the last two decades.

5.5. Rotating biological contactor Rotating biological contactor (RBC) is also another type of fixed film biological reactor in which series of circular plastic discs or plates are supported on a common horizontal shaft (Fig. 3(b)). This horizontal shaft rotates the partially submerged disc (40%) in a tank or contactor with the help of a power driven mechanism (motor) (Bull et al., 1982; Oğuz and Oğuz, 1993). Discs in RBC are usually 2–4 m in diameter, and generally made up by corrugated plastic material having sufficient surface area for the growth of microorganisms (Najafpour et al., 2005). Plates are sufficiently spaced up to 30–40 mm for suitable contact reaction between substrate, oxygen, and microorganism. Bacterial consortium grows rapidly on the surface of plates, and barely within a period of one week, about 1–4 mm thick biofilm can be observed on the plate surface. However, the thickness of the biofilm depends upon the rotational speed of the plates and wastewater strength. Microorganism degrades the organic content present in the wastewater by consuming oxygen from the atmosphere. Excessive growth of biomass is inhibited due to the shearing effect of wastewater on the media surface, and this result in sloughing of the biofilm. Low energy and maintenance cost, minimal requirement of skilled workers, capable of handling varying organic loads, and simplicity in construction are the chief advantages of RBC (Torkian et al., 2003a; Sirianuntapiboon, 2006). Additionally, RBC consumes less energy than ASP system and also it saves cost on capital investment due to no usage of pumps and recycling systems (Bull et al., 1982). Nevertheless, in spite of numerous advantages their execution in the treatment of slaughterhouse wastewater is very limited (Bull et al., 1982; Bustillo-Lecompte and Mehrvar, 2015; Johns, 1995). In early 1970s, a pilot scale study employing RBC as a post treatment unit after an anaerobic lagoon was done by (Chittenden and Wells Jr., 1971). Three stage configurations having 50 plates in each stage were used in RBC. Furthermore, three tests were conducted by varying the discharge and rotational speed of the shaft. The first test was conducted for a discharge of 38 m3/d, and at a rotational speed of 3 rpm in all three stages. The influent average BOD of 250 mg/l was reduced to 50% in the first test. While in the second test the removal efficiency was increased to 64.5% by solely increasing the shaft speed to 6 rpm (first stage only). And in the third test by keeping the rotational speed constant the discharge was reduced to 19 m3/d. The BOD removal efficiency as a result of that soared up to 83%.

Table 8 Performance of ASP over the last two decades for slaughterhouse effluent. Year

Scale

TCOD removal (%)

BOD removal (%)

O&G removal (%)

TSS removal (%)

References

2003 2004 2006 2008 2009 2011 2012 2015

Full Lab Lab Full Full Lab Lab Full

96 98 92 – 89 97.6 97 99

97 99.6 – 99 90 – – 99

88 – 92.5 95 – – – –

93 – – 92 94 – – 94%

Chen and Lo, 2003 Sroka et al., 2004 Rosa et al., 2006 Al-Mutairi et al., 2008 Pabón and Suárez Gélvez, 2009 Fongsatitkul et al., 2011 Hsiao et al., 2012 Amanatidou et al., 2016

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Johnson and Krill (1976) also evaluated the performance of RBC in meat processing and slaughterhouse effluent. The wastewater was preliminary treated in DAF system before its final secondary treatment. At different hydraulic loading rates (0.112, 0.53, and 1.06 l/d-m2) the average BOD of 650 mg/l was effectively reduced to 95%, 83%, and 64%. Effect of hydraulic loading rates on RBC was also evaluated by Oğuz and Oğuz (1993) while treating meat packaging plant wastewater. A total of six experimental runs were performed by varying the hydraulic loading rates. The results confirmed that on increasing the loading rates from 38 to 76 l/d-m2 resulted in declined removal efficiency for both BOD (80–56%) and TS (61–40%). In order to assess the feasibility of RBC after an UASB reactor a research was carried out by Torkian et al. (2003a). The study was performed in 280 l pilot scale RBC (6 stage) at various rotational shaft speeds and OLRs. The OLRs were varied from 5 to 18 g SBOD/m2-d in a span of six experimental tests conducted. Here also similar results of decreased BOD removal efficiencies were observed with increased loading rates. However, at 5.3 g SBOD/m2-d about 85% SBOD removal efficiency was attained. And thus, the wastewater can be suitably discharged for agricultural purposes at that particular loading rate. Thus, it can be inferred that RBC performance largely depends upon the influent wastewater concentration, organic and hydraulic loading rates, shaft rotational speed, and number of stages or units installed in RBC. Increased loading rates and wastewater strength can seriously affect the removal efficiency of RBC. In general, to obtain appropriate COD (b60 mg/l) and BOD (b25 mg/l) effluent concentrations, the RBC must be functioned at 65 g COD/m2-d and 22 g BOD/m2-d of loading rates respectively (Al-Ahmady, 2005). Moreover, according to Hassard et al. (2015), the RBC system is also capable enough in removing nutrients from the wastewater as well. 5.6. Moving bed biofilm reactor (MBBR) Moving bed biofilm reactor (MBBR) is said to be a modification of ASP system. The process was invented by Norwegian scientist in early 1990s (Zinatizadeh and Ghaytooli, 2015; Bassin et al., 2012). It combines the benefits of both ASP and biofilm reactor. Polyethylene carriers having a density close to water are used as media in MBBR (Borkar et al., 2013; Kermani et al., 2009). Unlike fixed film bioreactors, MBBR involves the movement of bio-carriers in the entire system to increase the contact area between substrates and biomass. The movement can be achieved either by aeration or by mechanical mixer depending upon type of bioreactor (aerobic or anaerobic) (Fig. 3(c)). The leading benefits of MBBR are resistant to shock loads, less volume requirement, no recycling or backwashing requirement, no mechanical intervention required in case of load fluctuations, and sufficient sludge retention time for both heterotrophic and autotrophic microorganisms (Camp et al., 2001; Joslin and Farrar, 2005; Zinatizadeh and Ghaytooli, 2015). The ability of MBBR to resist shock loads was evaluated by Hosseini and Borghei (2005) at lab scale. The authors concluded that MBBR was very effective in removing the contaminants from the wastewater, in spite of the fact that toxicity and hydraulic loading rates were varied up to an extent. Moreover, it was stated that the problem of sludge bulking was also prevented as a result of bio-carriers. Microscopic analysis confirmed the presence of filamentous bacteria only on the polyethylene carrier, and no such bacterial accumulation was observed in effluent wastewater. Camp et al. (2001) stated that MBBR is capable enough in degrading volatile organic compounds (VOC's) such as ethanol, methanol, acetone, isopropanol, and ethyl acetate. The findings demonstrated that two pilot stage MBBR systems were effective in removing 90% SCOD from the wastewater. Joslin and Farrar (2005) on the other hand evaluated the performance of two stage MBBR's at full scale while treating slaughterhouse effluent. The MBBR's were used as pre-treatment units before an activated sludge system. Pre-treatment through MBBR resulted in

695

increased treatment capacity, and N95% BOD was efficiently removed. And that ultimately resulted in increased discharge of treated water into nearby Norwalk river (US). MBBR unit was installed in a meat processing plant to meet the new US discharge standards (Colic et al., 2008). However, because of increased plant capacity and high concentration of contaminants, MBBR system was unable to perform satisfactorily. To enable the performance of MBBR, flotation unit was installed to reduce TSS, O&G, and BOD to a level that could be handled by MBBR. Additionally, about 50–80% of BOD was removed from the flotation system. Kermani et al. (2009) used a series of MBBR's (anaerobic, anoxic, and aerobic) in order to remove both phosphorous and nitrogen at lab scale. At steady state conditions 81% and 96% removal in total nitrogen and phosphorous removal efficiency was obtained. Stover-Kincannon model was used to analyse the behaviour of MBBR's with the experimental results. Excellent regression value was attained from kinetic analysis for both phosphorous (R2 = 0.9862) and nitrogen (R2 = 0.986) removal. In order to tackle the quandary of conventional nitrogen removal (nitrification and denitrification), Bertino (2011) developed partial nitrification (nitritation) process in a pilot scale MBBR. The removal efficiencies acquired from the system were 83% and 95% for TN and NH4 respectively. DO pH, ORP, and conductivity proved to be crucial in monitoring the reactor for 120 d. Bassin et al. (2012) employed two lab scales MBBR's to assess the time required in the development of microbial film on plastic media. The first reactor (MBBRA) was inoculated with already acclimatized nitrifying sludge in order to estimate the acclimatization time required when inorganic material is used as substrate. In contrast to that, the second bioreactor (MBBRB) was fed with compounds comprising of both organic and inorganic matter, and without acclimatized sludge. MBBRA took around 60 d to develop a thin secured microbial film while MBBRB acquired only 30 d to achieve a stable and thick biofilm on polyethylene media. However, the rate of nitrification was almost similar in both the cases, but only after the proper acclimatization and attachment of the biomass. Munir Baddour et al. (2016) estimated the performance of MBBR system in the treatment of poultry slaughterhouse effluent. The study initially calculated the system's performance in removing suspended and dissolved impurities over the acclimatized phase. Almost after one month the reactor was effectively removing 94% COD, 51% NO−3, 34% orthophosphate (PO−3 4 ), and 53% total dissolved solids (TDS) from the wastewater. Mannina et al. (2016) demonstrated the feasibility of combining MBBR with membrane bioreactor (MBR) in the removal of nutrients and carbonaceous compounds. A pilot scale study was done at different sludge retention times (infinite, 30 d, and 15 d) during the course of research. The pilot plant consisted of anaerobic, anoxic, aerobic bioreactors, and an MBR tank. Only anoxic and aerobic reactors were fed with plastic media. Despite the variation in SRT's, neither COD removal nor nutrients removal was affected. The maximum COD, ammonia, total nitrogen, and phosphorous removal efficiencies were 99%, 97%, 90%, and 70% respectively. Apart from that, it was inferred that suspended biomass culture was effective in removing carbonaceous compound, whereas attached microbes were efficient in eliminating ammonia from the wastewater. 5.7. Intermittent sequencing batch reactor An intermittent sequencing batch reactor (ISBR) is implemented in the removal of not only organic compounds but in the abstraction of nitrogen and phosphorous as well. It possesses copious advantages over other conventional aerobic systems. Feeding, reaction, settling, and decanting all takes place one after the other in one complete cycle. Aerobic, anoxic, and anaerobic conditions can be prevailed in a single batch reactor for the removal of impurities particularly N&P (Fig. 3(d)).

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However, the effluent characteristics depend largely upon aeration rate, OLRs, HRT, SRT, MLSS, specific oxygen uptake rate (SOUR), temperature, and F/M ratios. Moreover, COD/TN and COD/TP ratios are also significant in order to remove nutrients. Subramaniam et al. (1994) utilized two separate SBR's to treat slaughterhouse effluent after anaerobic ponds. The sole difference between the two SBR's was the influent characteristics. The first SBR received comparatively higher COD/TKN and SCOD/TP ratios. Thus, the removal efficiency achieved as a result of that was 90%, 92%, and 95% for TP, TKN, and COD respectively in the first reactor. In another similar case study yet again two sequencing batch reactors were employed after anaerobic ponds (Keller et al., 1997). Intermittent aeration strategy was adopted for the removal of contaminants. More than 97% ammonia removal and considerable elimination of nitrate and nitrite was observed from bioreactors. Additionally, around 75–85% phosphorous was also removed from post aerobic system. Obaja et al. (2003) conducted an extensive research by installing an SBR for the treatment of high strength ammonium rich compounds. A total of four experiments were conducted with varying concentrations of NH4 and PO−3 4 in a lab scale reactor (3 l). Anaerobic, aerobic, and anoxic conditions provided the effluent that was free from nitrogenous compounds. The maximum percentage removals of ammonium, nitrate, and phosphate in all the four experiments conducted were 99.7%, 99.9%, and 97.8% respectively. Furthermore, effect of temperature was also analysed, and it was concluded that SBR was efficient in removing NH4 even at 16 °C. Study on SBR running on SWW at 22 °C was done by Thayalakumaran et al. (2003). Nitrogen, nitrite, and nitrate concentrations were reduced to a value b10 mg/L, 1 mg/l, and 5 mg/l respectively, while total phosphorus to a value b1 mg/L. Moreover, around 94% suspended solids and 99% SCOD removal was also observed. Inverse relationship of pH and alkalinity was reported during initial aerobic and anaerobic stages. This is due to generation and stripping of carbon dioxide gas. Marcinkowski et al. (2004) estimated the functioning of ISBR in case of cattle slaughterhouse wastewater. The study demonstrated the feasibility of partial nitrification (nitritation) and denitrification process in the removal of nitrogenous compounds (200–600 mg/l) from a Danish slaughterhouse (Denmark). ISBR having a working volume of 3 l was operated at 35 °C for both aerobic (5 h) and anoxic cycles (3 h). Ample nitrification and denitrification were observed with an average removal efficiency of 72% (0.3 g NH4/g VSS-d) and 96% (0.042 g NO−2/g VSS-d) respectively. A recent and effective technique for the removal of nutrients is aerobic granulation (Sengar et al., 2018b). According to Zhang et al. (2016), aerobic granules possess compact core like structure that are large in size, and therefore are beneficial in treating industrial wastewaters. Aerobic granulation process has certain advantages such as low operation expenses, no secondary clarifier requirement, adjustable to sudden high loadings, and possibility of achieving denitrification in settle and anoxic phases (Nancharaiah et al., 2016). Gao et al. (2011) also talked about zonal distribution in granules based on DO gradient. There is existence of aerobic zone on the outside (for organic matter removal), nitrification zone in middle and at centre there is presence of anoxicanaerobic zone. Simultaneous phosphate and nitrogen removal is shown by aerobic granules in many studies (De Kreuk et al., 2005; Lemaire et al., 2008b; Bao et al., 2009; He et al., 2018). Cassidy and Belia (2005) achieved simultaneous nitrogen and phosphorus removal by using granular sludge from slaughterhouse wastewater. Settling time was reduced from 60 to 2 min, and granules were developed within quick interval of 4 d. Granules of size 1.70 mm were reported having 22 ml/g of sludge volume index (SVI). Removal efficiency of nitrogen and VSS were over 97%, and of phosphate and COD were beyond 98%. Aerobic granules formation was also studied by Kishida et al. (2009) by installing an ISBR (4.5 l) for treating synthetic and livestock

wastewater. Formation of granules was first observed in case of synthetic wastewater. Thereafter, when the livestock wastewater (diluted) was treated then also the development of granules was examined. Moreover, removal of nutrients occurred in spite of excessive suspended solids. However, for undiluted livestock wastewater the treatment efficiency decreased with decline in granules structure. Nevertheless, the efficiency soared again by improving the excess sludge discharge techniques, and thus effective removal of nutrients was acquired. Liu et al. (2015) also reported the formation of granules while treating slaughterhouse wastewater. Maturation of granules was achieved at lab scale after 90 d of operation. Removal efficiencies reported were 95.1%, 83.5%, and 99.3% for COD, phosphate and ammonia respectively. Specific oxygen uptake rate (SOUR) analysis was performed, and it revealed that ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were increased with granulation. How carbon to nitrogen ratio (C/N) affects simultaneous nitrification and denitrification (SND) was shown in a study by Chiu et al. (2007). While having a ratio of 11.1 of COD/NH4, complete ammonium and COD removal was obtained and nitrite was not present in the effluent. With increase in the loading of ammonium, removal efficiency of nitrogen was found to be decreased. Besides C/N readily biodegradable to soluble COD ratio also plays a key role in SND (Khursheed et al., 2018). Hence, it should also be properly considered while removing nitrogenous compounds. On the other hand, DO concentration is also the fundamental controlling factor. For complete nitrification a minimum of 2 mg/l DO is required (Gerardi, 2003; Sriwiriyarat et al., 2008). Microbial consortium can be greatly influenced by the change in DO (Cabezas et al., 2006). An ISBR was used for improving water quality of shrimp aquaculture (Boopathy et al., 2007). Nitrification and denitrification were achieved by SBR on operation under sequential aerobic (2 d) anoxic (3 d), and aerobic (2 d) cycles. In the course of research period, complete nitrification and denitrification was achieved. Furthermore, the COD removal efficiency from ISBR was about 97%. Study was made on SBR running on intermittent mode and treating SWW (Li et al., 2008b). In the react phase, intermittent aeration was provided for four times for 50 min, and having an interval of 50 min at 0.80 L/min of air supply rate. Influent concentration of impurities was reported as, COD - 4672 mg/L, TN - 356 mg/L and TP - 29 mg/L with minor variation. Removal efficiency achieved was 96% for both COD and TN, and 99% for TP. Additionally, it was discovered that 66% nitrogen was removed because of denitrification, while the rest (34%) due to biomass synthesis. Enhanced denitrification was achieved by using low DO level in lab scale SBR by Zhan et al. (2009). Study on nitrogen removal was performed by using intermittent and continuous aeration operating strategy. It was found that, 95% of total nitrogen was removed while operating the SBR on intermittent mode, while continuous aeration strategy yielded nitrogen removal of 91%. Moreover, in continuous aeration mode, pre-denitrification was done and low DO levels were applied to achieve nitrogen removal from SWW. Furthermore, 65% savings were reported in electricity consumption by maintaining low dissolved oxygen content under intermittent mode strategy. Apart from that, COD and SS removal efficiencies in both the cases were over 99%. SBR was used to treat SWW for producing effluent having desirable levels of phosphorus and nitrogen for irrigation purpose (Pijuan and Yuan, 2010). The chief purpose of the study was to accomplish denitrification process by the means of nitrite as an electron acceptor instead of nitrate. As a result of that, considerable reduction in additional carbon source and oxygen was observed. The results showed that oxygen and carbon source requirements were reduced by 25% and 40% respectively. Additionally, the TCOD (77%), TKN (83%), and TP (66%) were efficiently removed from the wastewater. In order to estimate the performance of SBR at different aeration rates, Pan et al. (2014a) carried out an investigation at

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aeration rates of 0.40, 0.60, and 0.80 l air/min. Three intermittent SBRs each having 8 l working volumes were operated at an average loading rate of 0.61 kg COD/m 3 -day. Cycle duration chosen was 12 h, and efficient COD (98%), TN (98%), and TP (96%) removal was obtained at 0.60 l air/min. Also, elevated nutrients removal was observed at lower aeration rates (0.40 and 0.60 l air/min). However, lower dissolved oxygen can influence the production of nitrous oxide (N 2 O) in conventional nitrification-denitrification processes. N2O is considered to be the leading cause of ozone depletion, and therefore a primary greenhouse gas (Adouani et al., 2010). Pan et al. (2014b) demonstrated that the percentage of N 2O depends upon the influent TN concentration. About 6–11% N2O was liberated at 576 mg/l TN concentration. Additionally, as the aeration rates were increased from 0.4 l air/min to 0.8 l air/ min in intermittent SBR, N 2O emission/incoming total nitrogen ratio was decreased by 48.2%. Table 9 demonstrates numerous case studies conducted in the treatment of slaughterhouse waste by installing sequencing batch reactors.

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thus, can be easily discharged to lands or aquatic bodies. The benefits of sequential treatment are complete degradation of organic matter, substantial production of biogas, removal of both nitrogen and phosphorous, elimination of heavy metals, phenols, and pharmaceutical compounds (Armenante et al., 1999; Joss et al., 2004; Ağdağ and Sponza, 2005; Lemaire et al., 2008a; Shi et al., 2014). Several studies have been conducted in the treatment of slaughterhouse wastewater by combining both anaerobic and aerobic reactors (Table 10). 7. Microbial community responsible for slaughterhouse waste treatment Analysis of microbial community is essential during biological waste treatment. However, in case of slaughterhouse waste limited studies are available in literature. Studies conducted are mostly related to quantification of anaerobic microorganisms. Nevertheless, following section illustrates the role of anaerobic and aerobic species in degrading complex compounds during waste generated from slaughterhouse industry. Cabezas et al. (2006) carried out a research on the effectiveness and diversity of microbial species treating slaughterhouse wastewater under low DO conditions in SBR. The objective was to supress NOB in order to make the process more efficient. The DO in anoxic phase was between 0.7 and 0.9 mg/l, while 2–3 mg/l in the aerobic phase. Under oxygen limited supply NOB activity were supressed, but after increase in DO Nitrobacter were again prevalent inside ISBR. AOB bacteria particularly Nitrosomonas were comparatively stable during the investigation. Nitrosospira, and Nitrosococcus were also present but in lower fractions. Thauera and Pseudomonas were the dominant denitrifiers during anoxic conditions.

6. Sequential anaerobic and aerobic treatment for slaughterhouse wastewater Organic and inorganic compounds can be greatly reduced by combining both anaerobic and aerobic processes. Numerous sequential case studies have been conducted in the treatment of both domestic and industrial wastewaters (Castillo et al., 1999; Işik and Sponza, 2004; Işik and Sponza, 2006; Tezel et al., 2001; Von Sperling et al., 2001). Fig. 4 shows some of the schematic diagrams of sequential anaerobic and aerobic processes. Anaerobic-aerobic treatment provides the effluent that can be met with the international design standards. And

Table 9 Removal of COD, BOD, nitrogen and phosphate from SBR at different operating conditions. Reactor Working volume (l)

HRT

SRT

Loading rates Temperature COD (°C) (%)

BOD Nitrogen Phosphate SS MLSS (%) (%) (%) (%) (g/l)

ISBR ISBR

40 7.9

12 h 2d

– –

– –

– 20 ± 2

98 96

ISBR

7.9

2d

20 d

–

20 ± 2

96

ISBR

7.5

1.5 d

6.8 d

–

94

MSBR

–

–

–

0.264 kg BOD/m3-d –

–

98

99.6 98 (TN) – 97 (TKN) – 98 (TKN) 96 93 (TKN) 98 95 (AN)

ISBR ISBR

7 10

42 h –

15 d 14.5 d

18–22 –

95 97

– –

ISBR

10 (TV)

12 h

21–67 d

– 1.4 kg COD/m3-d 0.19 ± 0.03 kg N/m3-d

29 ± 2

64

ISBR ISBR

5 2

16 h 2d

20

10 h

– 0.15 kg N/m3-d –

25 ± 1 20

ISBR

–

ISBR ISBR

4.5 5

23 h 16 h

– N 100 d 20–25 d – –

ISBR

8

10 d

20 d

ISBBR

8

24 h

–

IAASBR

12 (An), 6 (Ae)

48 h (An), 24 h (Ae)

40 d (An), 15 d (Ae)

– 0.15 kg N/m3-d 0.61 kg COD/m3-d 1.88–6.77 kg COD/m3-d 0.5–4.5 kg COD/m3-d

MLVSS (g/l)

F/M

SVI (ml/g) – –

87 84

– 80

– –

– 4.09

– –

–

88

4.5–7

3.5–5

–

72

–

2.5

–

0.091

98

93

–

–

–

97 (TN) 95 (TN)

98 97

– –

– – 3.85–4.95 –

– –

–

83 (TKN)

25

25

3.3–5.6

54 –

– –

84 (TIN) 90 (AN)

– –

– –

– – –

11

98

–

70–98 (AN) – 91.1 (TIN) 98 (TN)

–

– 21.5 ± 0.85

86–95 (SCOD) 74–94 –

25–30

98

–

26–28

97%

–

References

Sroka et al., 2004 Filali-Meknassi et al., 2005a 50–100 Filali-Meknassi et al., 2005b 73 Sirianuntapiboon and Yommee, 2006 – Shengquan et al., 2008 – Lemaire et al., 2008a 90–140 Li et al., 2008a 118 ± 35

De Nardi et al., 2011

– 3

1.8–3.5 0.06 ± 0.03 2.6 – 2.5 –

– 110

Mees et al., 2011 Li et al., 2011

–

–

1.8–3.2 –

75–85

Kundu et al., 2013

– –

– –

7 –

– 2.6

– –

– –

Louvet et al., 2013 Mees et al., 2014

96

–

4.2

–

–

–

Pan et al., 2014a

96 (TN)

96

–

–

–

–

–

Hai et al., 2015

98 (AN)

–

96

6000 (An), 4000 (Ae)

–

–

150

Rajab et al., 2017

ISBR - Intermittent sequencing batch reactor; MSBR - Membrane sequencing batch reactor; ISBBR - Intermittent sequencing batch biofilm reactor; IAASBR - Integrated anaerobic/aerobic sequencing batch reactor; TN -Total nitrogen; TKN - Total kjeldahl nitrogen; TIN - Total inorganic nitrogen; AN - Ammonia nitrogen; SCOD – Soluble COD; TV - Total volume; An - Anaerobic; Ae – Aerobic.

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Fig. 4. Schematic diagrams of sequential anaerobic and aerobic processes: (a) Willers et al., 1993 (b) Bernet et al., 2000; Mutua et al., 2016; Aziz, 2018 (c) Núñez and Martínez, 2001 (d) Del Pozo and Diez, 2005 (e) Merzouki et al., 2005 (f) López-López et al., 2010 (g) Fongsatitkul et al., 2011 (h) Basitere et al., 2016 (i) Bustillo-Lecompte and Mehrvar, 2017b

Lemaire et al. (2008b) examined the microbial species in aerobic granules for simultaneous removal of nitrogen and phosphate. Accumulibacter (polyphosphate accumulating organism, PAO) and Competibacter (glycogen accumulating organism, GAO) accounted

for almost 75%, both of which can perform denitrification. Accumulibacter was dominant in the outer 200 μm, while Competibacter was present in the central part of granule having size N500 μm.

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

699

Table 10 Execution of different sequential assemblies (anaerobic-aerobic) and their final conclusions in the treatment of high strength industrial wastewater (slaughterhouse). S.·no Sequential assembly 1

2

3

4

5

6

7

8

9

10

The sequential configuration consisted of anoxic and aerobic reactors and a clarifier for separating solids from liquid (Fig. 4(a)).

Wastewater composition

Conclusion

References

Nitrogen removal rates varied linearly with Influent waste comprised of high COD (13 g/l), BOD (7.2 g/l), NH4-N (2.2 g/l), TKN (2.5 g/l), and temperature. Maximum nitrogen removal rate TSS (14.4 g/l). (154 mg NH4-N/g VSS-d) was observed at 20 °C. Moreover, anoxic/aerated volume ratio of 0.25 is suggested at BOD/NH4-N ratio of 2.4 for complete denitrification. Additionally, an increase in recirculation factor from 15 to 30 didn't cause any significant effect on BOD removal rates. Excellent TOC (81–91%) and TKN (85–91%) Two sequencing batch reactors were installed The piggery wastewater after preliminary removal was observed from anaerobic-aerobic one after the other. The first was anaerobic treatment consisted of TOC - 5.86 g/l, TKN and the second was aerobic SBR (Fig. 4(b)). 3.69 g/l, NH4-N - 2.94 g/l, TSS - 2.84 to 3.96 g/l. system. Elevated nitrogen removal was acquired with increased recycling ratios. Furthermore, biogas was mainly comprised of N2 and CH4, which demonstrated that methane production followed denitrification in anaerobic SBR. An upflow anaerobic sludge blanket reactor Slaughterhouse wastewater comprised of TCOD (85%) removal efficiency was independent coupled with activated sludge system was combination of blood, protein, fats, and manure. from recycling ratios. But TKN and TN removal employed for treating slaughterhouse efficiencies increased to 85% and 70% wastewater (Fig. 4(c)). respectively at recycling ratio of 2. However, at that particular ratio carbon removal efficiency in UASB decreased. A pilot scale anaerobic-aerobic fixed film The average COD, BOD, TKN, TSS, and O&G were At an average loading rate of 0.77 kg COD/m3-d and 0.084 kg N/m3-d the TCOD and nitrogen reactor was established for poultry 1820 mg/l, 900 mg/l, 190 mg/l, 430 mg/l, and removal efficiencies were 93% and 67% slaughterhouse wastewater (Fig. 4(d)). 170 mg/l respectively. respectively. Additionally, the biogas generated consisted of about 58% N2, 37% CH4, and 5% CO2. The wastewater was prefermented for 14 d in To reduce nutrients and carbonaceous The wastewater treated was having average order to increase phosphate and VFAs compounds a combination of TCOD of 7.78 g/l, NH4-N of 88 mg/l, TKN of 410 mg/l, PO4-P of 18 mg/l. concentrations. The average removal anaerobic-anoxic SBR and aerobic fixed bed efficiencies soared from 83% to 94%, 48.5% to reactor was used for slaughterhouse effluent 77%, and 47% to 97% for COD, NH4-N, and PO4-P (Fig. 4(e)). respectively. Anaerobic filter performed exceptionally at 24 Anaerobic filter and aerobic sequencing batch Slaughterhouse wastewater showed COD h HRT and 11 kg/m3-d of OLR. In case of SBR reactor were installed for treating high 11000 mg/l, BOD 8360 mg/l, TSS 8150 mg/l, the reactor was proficient at 9 h aeration strength industrial wastewater (Fig. 4(f)). ammonia nitrogen 137 mg/l, PO−3 4 -P 83 mg/l, and O&G 784 mg/l. period. The combined arrangement removed about 97% COD, 99% BOD, 99% TSS, 93% ammonia nitrogen, 80% PO−3 4 -P, and 83% O&G from the wastewater. A series of anaerobic, anoxic, and aerobic The influent wastewater comprised of high Effect of internal recycle on the removal reactors were employed for the treatment of organic and inorganic content. The average COD, efficiencies of COD, TKN, and TP was slaughterhouse wastewater (swine) (Fig. 4 TKN, TP, and TSS were 1551 mg/l, 189 mg/l, 28.6 analysed by changing the discharge from 15 (g)). mg/l, and 521 mg/l respectively. to 40 l/d. At 30 l/d both TKN and TP achieved excellent removal rate of 97.6% and 89.5% respectively. Furthermore, COD removal was mostly above 95% at different flow rates. Anaerobic expanded granular sludge bed Here again the wastewater constitute excessive At different organic loading rates (0.5, 0.7, and 1 (EGSB) reactor attached with sequential amount of TCOD (2133–4137 mg/l), BOD kg COD/m3-d) and hydraulic retention times (7, 4 and 3 d), the removal efficiency of entire anoxic and aerobic reactors was operated for (1100–2750 mg/l), FOG (131–684 mg/l), TKN system and EGSB reactor was 65% and 51% a period of 26 d in order to treat poultry (77–352 mg/l), TP (8–27 mg/l), and TSS respectively. Low COD removal was observed slaughterhouse wastewater (Fig. 4(h)). (315–1273 mg/l). due to sludge washout from EGSB because of the presence of elevated suspended solids and fats. Hence, installation of dissolved air floatation before EGSB reactor was recommended by authors. The meat processing wastewater was treated Considerable high concentrations of TCOD The reactors were functioned at an SRT of 5 d, effectively by establishing lab scale anaerobic (15,812 mg/l), BOD (13,659 mg/l), TKN while the HRT was fixed at 2 d and 1 d for and aerobic sequencing batch reactors in (1022 mg/l), and TP (61 mg/l) was obtained anaerobic and aerobic SBR respectively. At an series (Fig. 4(b)). from meat processing plant. OLR of 12.8 kg COD/m3-d the reactor removed 99% COD and BOD, 96% TKN, and 61% TP efficiently from the wastewater. Anaerobic baffled reactor coupled with Maximum COD, TOC, TP, TN, and TSS observed At optimal operating conditions maximum TOC activated sludge reactor was implemented at during the research period were 2080 mg/l, (85%) and TN (72%) removal was obtained from lab scale in the treatment of Ontario meat 1694 mg/l, 23 mg/l, 255 mg/l, and 103.5 mg/l the system. About 0.12 m3/d methane or 0.48 kWh daily energy productions was observed processing wastewater (Fig. 4(i)). correspondingly. from anaerobic baffled reactor. In addition to that the projected model can be used in nearby future in case of anaerobic and aerobic treatment because of the fact that it provided eminent results.

Willers et al., 1993

Bernet et al., 2000

Núñez and Martínez, 2001

Del Pozo and Diez, 2005

Merzouki et al., 2005

López-López et al., 2010

Fongsatitkul et al., 2011

Basitere et al., 2016

Mutua and Mwaniki Njagi, 2016

Bustillo-Lecompte and Mehrvar, 2017b

(continued on next page)

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Table 10 (continued) S.·no Sequential assembly

Wastewater composition

Conclusion

11

The slaughterhouse wastewater comprised of high COD (3800–4700 mg/l), BOD (2300–3100 mg/l), TN (210–274 mg/l), PO−3 4 (140–229 mg/l), TSS (794–1116 mg/l), and O&G (426–521 mg/l).

The combined sequential assembly removed Aziz, 2018 about 92% COD, 97% BOD, 90% TSS, 74% PO−3 4 , and 90% O&G from the wastewater. Moreover, production of biogas rich in methane was also observed from ASBR. The average biogas and methane production at steady state conditions were 3.95 l/day and 64% respectively.

Slaughterhouse wastewater was sequentially treated by anaerobic and aerobic sequencing batch reactors (Fig. 4(b)).

Lemaire et al. (2009) established a lab scale SBR in the removal of phosphorous, nitrogen, and TCOD from slaughterhouse wastewater. Initially SBR was fed with non-enhanced biological phosphorous removal sludge, but later on enhanced biological phosphorous removal sludge was added to SBR. Fluorescence in situ hybridisation confirmed the presence of Accumulibacter species (70%). After achieving the steady state the removal efficiencies were 95%, 98%, and 97% for TCOD, total phosphorous, and total nitrogen respectively. Rajakumar et al. (2011) employed an upflow anaerobic filter to treat Indian poultry slaughterhouse wastewater. Maximum removal in TCOD (78%) was observed at 12 h HRT and 10.05 kg/m3-d of organic loading rate. Additionally, average methane content was between 46 and 56% during the investigation. SEM analysis showed granules clumps comprised of Methanosarcina (dominant) and Methanosaeta cells. Methanosarcina has higher substrate affinity for acetate than Methanosaeta at higher acetate concentrations. The acetate concentration was 980 mg/l, and therefore Methanosarcina presence was abundant inside anaerobic filter. Also Methanosarcina beside acetate can consume formate, hydrogen, and carbon dioxide as well, and thus was dominant than Methanosaeta. Palatsi et al. (2011) assessed the influence of increased loading rates by mixing different slaughterhouse waste (cattle/pig) on the activity of microbial species. Syntrophomonas, Coprothermobacter, Anaerobaculum, and Methanosarcina were responsible for stable reactor performance in spite of high lipid content. The authors suggested that microbial community and lipid concentration are the two important reasons for successful anaerobic treatment of slaughterhouse waste. In order to assess the bacterial community present in anaerobic lagoon (2000 m3), a study was performed by Cardinali-Rezende et al. (2012). The COD and BOD removal efficiencies were 55% and 58% respectively. Bacteroidetes, Chloroflexi, and Proteobacteria were the dominant bacteria, while archaeal group present in sludge was Euryarchaeota and Crenarchaeota. Crenarchaeota was responsible for ammonia oxidation, and Euryarchaeota (Methanomicrobiales and Methanobacteriales) for producing methane. Rajakumar et al. (2012) performed anaerobic experiments at mesophilic conditions (29–35 °C) to evaluate the microbial species involved in the degradation of poultry slaughterhouse wastewater. Change in species were observed during the course of 225 days. During startup period Methanobacterium and Methanosaeta were dominant, while Methanosarcina was prevalent at the end of study. A study on temperature effect (mesophilic and thermophilic temperature) on COD removal in upflow anaerobic filter was conducted by Gannoun et al. (2013). 90% (mesophilic) and 72% (thermophilic) COD reduction was observed at OLRs of 4.5 g COD/l-d and 9 g COD/l-d respectively. Microbial analysis showed dominant fermentative bacteria, and Clostridiales group contained maximum number of strains. Three novel strains identified were Macellibacteroides fermentans, Desulfotomaculum peckii and Defluviitalea saccharophila. Stets et al. (2014) conducted a study to evaluate the performance of AF by using three different types of support media (Polypropylene rings, polyurethane foam, and clay brick) in three different reactors. All three reactors showed similar microbial composition, but clay brick reactor showed highest bacterial and archaeal compositions.

References

Proteobacteria and Bacteroidetes were the dominant bacteria, while Methanomicrobiales and Methanosarcinales were the common archaea present. Moestedt et al. (2016) demonstrated the significance of trace elements (Fe, Co, and Ni) during anaerobic co digestion of slaughterhouse and municipal solid waste. Real time PCR was performed to quantify methanogens including Methanobacteriales, Methanococcales, Methanomicrobiales, Methanosaetaceae, and Methanosarcinaceae. Fe, Co, and Ni were added to experimental and control anaerobic reactors during different phases. However, day 0 was set when Co supplementation was stopped in control reactor. During days 32 and 81, Methanomicrobiales were dominant (23–41%) in both reactors, while after 90 days Methanosarcinaceae abundance increased considerably in experimental reactor when fed with Ni. Moreover, reduction in Methanomicrobiales and Methanosaetaceae communities was observed as a result of Ni and Co addition in experimental reactor. Pagés-Díaz et al. (2015) evaluated methanogenic community during the operation of four continuously stirred anaerobic digesters treating different waste mixtures. The reactors were operated at 55 °C with slaughterhouse waste (SW), slaughterhouse waste manure (SW M), slaughterhouse waste various crops (SW VC), and slaughterhouse waste various crops municipal solid waste (SW VC MSW). Methanomicrobiales, Methanobacteriales, Methanosarcinaceae, and Methanosaetaceae were targeted initially and at the end of study. M ± ethanosaetaceae was absent in inoculum as well as in digested sludge. Methanosarcinaceae presence increased in all four reactors with dominance in SW M reactor. Methanosarcinaceae group are responsible for directly converting acetate into methane by acetoclastic pathway. Methanomicrobiales on the other hand was supressed in all reactors because of elevated pH (N7). Thus, Methanobacteriales were utilizing hydrogen to produce methane instead of Methanomicrobiales. Maximum methane production was 5.3 l/d in SW M reactor, while minimum was 1.1 l/d in SW reactor. The bacterial community treating abattoir wastewater was analysed by Jabari et al. (2016). The anaerobic digester (upflow anaerobic filter) operated at both mesophilic and thermophilic conditions. Results revealed 27 different phyla comprising mainly of Firmicutes (21.7%), Proteobacteria (18.5%), Bacteroidetes (11.5%), Thermotogae (9.4%), Euryarchaeota (8.9%), and mslb6 (8.8%). Clostridium, Bacteroides, Desulfobulbus, Desulfomicrobium, Desulfovibrio and Desulfotomaculum were the dominant bacteria in the anaerobic sludge. Hernández et al. (2016) observed the role of microalgae for the production of biofuel in two 75 l high rate algal ponds. One pond was operated indoors under controlled temperature (25 ± 2 °C) and light supply, while the other was placed in greenhouse conditions with 20 ± 6 °C and higher light supply. Initial mix microalgae comprised of Chlamydomonas subcaudata, Anabaena and Nitzschia species. High COD removal efficiency (92%) was achieved in algal pond kept indoors, whereas high soluble phosphorous (71%) removal was acquired at greenhouse conditions. The role of mixed algal species on nutrients removal from slaughterhouse wastewater was examined by Taşkan (2016). After acclimatization the photo-bioreactor removed about 90% TOC, 96% total phosphorous, and 70% total nitrogen. Cyanobacterial species were

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(a) Thermotogae Spirochaetes WWE1 OP11 Verrucomicrobia Actinobacteria WS6 Planctomycetes Synergistetes Bacteroidetes Chloroflexi Firmicutes Proteobacteria Euryarchaeota 0

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(b) Fig. 5. (a) Krona chart represents overall anaerobic microbial community of sludge obtained by 16S rRNA sequencing, (b) represents bacterial and archaeal community at the phylum level, (c) represents bacterial and archaeal community at the class level. (Aziz, 2018).

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Thermoplasmata Mollicutes Thermoleophilia Unclassified Coriobacteriia Bacilli TM7-3 Verruco-5 Unclassified Thermotogae Alphaproteobacteria [Pedosphaerae] Spirochaetes Betaproteobacteria Actinobacteria [Cloacamonae] WCHB1-64 Gammaproteobacteria Methanobacteria SC72 Epsilonproteobacteria Planctomycetia Synergistia Bacteroidia Deltaproteobacteria Anaerolineae Clostridia Methanomicrobia 0

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(c) Fig. 5 (continued).

more efficient than eukaryotic in the removal of nutrients from slaughterhouse wastewater. A study on the bacterial composition of a full scale UASB reactor treating slaughterhouse wastewater by two different sequencing approach (16SrRNA and whole genome shotgun metagenomic) was conducted by Delforno et al. (2017). Different type of sequences were quantified by the two approaches. At genus level, Clostridium and Methanosaeta were detected by 16S rRNA and Pseudomonas and Psychrobacter by whole genome shotgun metagenomics. Methanosaeta was more abundant than other hydrogenotrophic and methylotrophic methanogens. Moreover, antibiotic resistant genes (ARGs) were also classified, and total of 43 different ARGs were present. Multidrug, bacitracin, tetracycline, lincomycin, and polymyxin genes were abundant (N95%) in total sludge sample. Granada et al. (2018) performed a detailed study on biogas production and microbial composition during anaerobic digestion of slaughterhouse and dairy industrial waste. At the end of the study about 38 l biogas comprising of 26 l methane and 12 l other gases was produced. Samples were collected on day 1, day 7, day 25, and day 42 for microbial analysis. Phylum Firmicutes and classes Clostridia and Bacilli were abundant in all four sampling days. Clostridia species are responsible for producing important VFAs such as acetate, butyrate, formate, and lactate, whereas Bacilli efficiently improves the organic matter degradation. Apart from that, both of them also act as important denitrifiers. In addition to that, particular bacterial and archaeal species which were actively responsible for methane production were Porphyromonadaceae, Tissierellaceae, Methanobacteriaceae, Methanosarcina, Caldicoprobacteraceae, Syntrophomonadaceae, Bacteroidaceae, Turicibacteraceae, and Dethiosulfovibrionaceae. Porphyromonadaceae and Tissierellaceae are responsible for degrading complex compounds such as proteins, carbohydrates, and peptides, and in the production of VFAs. Methanobacteriaceae utilize CO2/H2 as substrate for methane production, and Methanosarcina beside active methanogen is also resistant to variation in temperature, loading rates, and ammonium toxicity.

Yan et al. (2018) studied the effect of change in initial sludge pH (6.5 to 8) during anaerobic digestion of slaughterhouse wastewater sludge. The authors exhibited that increase in pH resulted in increased biogas (10%) and methane (64%) production, while decreased hydrogen sulphide content (45%). Microbial analysis revealed Euryarchaeota, Proteobacteria, Bacteroidetes, Proteobacteria, and Firmicutes as dominant phylum. Methanogens belongs to Euryarchaeota, while sulphate reducing bacteria belongs to Proteobacteria family. Firmicutes are responsible for degrading VFAs into hydrogen, and Bacteroidetes converts amino acids into acetate. Methanogens, sulphate reducing bacteria, and Firmicutes were higher at pH 6.5 than at pH 8. Bacteroidetes showed contrary result, and was 5% higher at pH 8 than at pH 6.5. Methanogens quantified at genus level were Methanosaeta, Methanobacterium, Methanosarcina, Methanobreribacter, Methanospirllum, and Methanolinea. Methanospirllum and Methanosaeta percentage were not affected by initial pH change, whereas Methanobacterium percentage was higher at 6.5 than at pH 8. Methanosaeta utilize acetate, while Methanospirllum and Methanobacterium consume hydrogen to produce methane. On the other hand, Methanosarcina abundance increased by 25% when pH was increased from 6.5 to 8. Moreover, Methanosarcina can utilize both acetate and hydrogen to produce methane. Thus, Methanosarcina presence elevated the methane production at pH 8. Aziz (2018) evaluated the performance of anaerobic SBR in the treatment of slaughterhouse wastewater. TCOD, SCOD, BOD, and TSS removal efficiency acquired from anaerobic digester were 68%, 69%, 71%, and 63% respectively. The average biogas production and methane percentage was 3.95 l/day and 64% respectively. 16S rRNA sequencing analysis showed Proteobacteria, Firmicutes, Chloroflexi, Bacteroidetes, Planctomycetes, and Euryarchaeota abundance at phylum level (Fig. 5(a)). Bacteroidetes and Firmicutes phylum are responsible for degrading complex compounds i.e., proteins, lipids, and polysaccharides into acetate, CO2, formate, LCFAs, and hydrogen (Jabari et al., 2016; Stets et al., 2014). Proteobacteria classified at class level were alphaproteobacteria, betaproteobacteria,

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gammaproteobacteria, deltaproteobacteria, and epsilonproteobacteria (Fig. 5(c)). Gammaproteobacteria group comprises of denitrifiers and phosphate accumulating organisms. Deltaproteobacteria contains bacteria which are mainly responsible for sulphate reduction, and betaproteobacteria community are responsible for nitrification and sometimes in denitrification as well (Jabari et al., 2016). Chloroflexi phylum are involve in the production of acetic acid, and degradation of both monosaccharides and polysaccharides (Zheng et al., 2015). They are also effective in degrading difficult organic compounds during anaerobic digestion. Planctomycetes utilize glucose, maltose, and ribose (monosaccharides) to convert them into acetic acid and hydrogen (Zheng et al., 2015). Methanomicrobia (27%) and Methanobacteria (2%), were the two main methanogenic groups observed at class level under Euryarchaeota phylum (Fig. 5). The dominant Methanomicrobia class usually comprises of two important orders i.e., Methanosarcinales and Methanomicrobiales. Methanosarcinales are sheathed rods, cocci, and pseudosarcina in shape, and utilize acetate, methanol, methylamine, H2 and CO2 to convert them into methane. On the other hand, Methanomicrobiales (sheathed rods, spirals, rods, and cocci) consumes H2, CO2, and formate to produce methane. The other methanogenic group classified was Methanobacteria, which comprises of Methanobacteriales at order level. They are in cocci and rod shapes, and produce methane by utilizing H2, CO2, formate, CO, methanol, and secondary alcohols (Liu, 2010). 8. Conclusion The type of treatment generally depends upon wastewater characteristics, effluent guidelines, and the best available technology. Reactors such as UASB, AF, RBC, ASP, MBBR, and SBR have successfully executed in the treatment of slaughterhouse effluent. Thus, in order to reduce both organic and inorganic content either single intermittent SBR or combined sequential assemblies (anaerobic and aerobic) must to be implemented. Execution of single ISBR proves to be beneficial than combined reactors as it has resulted in reduced aeration rates with concurrent elimination of external carbon source. But certain conditions like anaerobic and aerobic reaction time, loading rates, mixing rate, DO, HRT, SRT, MLSS, F/ M, and SOUR ought to be controlled and monitored periodically. Moreover, aerobic granulation can also reduce carbon, nitrogen and phosphorous in ISBR. Although ISBR is a promising technology, it still needs to provide its competence by further conducting meticulous research at both pilot and real scale. Future research must be conducted on methane production and the role of aerobic and anaerobic microorganism particularly methanogens in ISBR during SWW treatment. Acknowledgement The corresponding author wish to thank the sponsors of this project “Bio-energy production from high strength industrial wastewater (slaughterhouse wastewater) with anaerobic SBR combining with aerobic SBR for safe discharge of treated water” for their financial support, namely Early Career Research Award, SERB, Department of Science and Technology (DST), New Delhi, India. Sanction Order No: ECR/ 2016/00162 Dated: 23 June 2017. References Adouani, N., Lendormi, T., Limousy, L., Sire, O., 2010. Effect of the carbon source on N2O emissions during biological denitrification. Resour. Conserv. Recycl. 54, 299–302. https://doi.org/10.1016/J.RESCONREC.2009.07.011. Ağdağ, O.N., Sponza, D.T., 2005. Anaerobic/aerobic treatment of municipal landfill leachate in sequential two-stage up-flow anaerobic sludge blanket reactor (UASB)/ completely stirred tank reactor (CSTR) systems. Process Biochem. 40, 895–902. https://doi.org/10.1016/J.PROCBIO.2004.02.021. Al-Ahmady, K.K., 2005. Effect of organic loading on rotating biological contactor efficiency. Int. J. Environ. Res. Public Health 2, 469–477. https://doi.org/10.3390/ ijerph2005030012.

703

Al-Mutairi, N.Z., 2009. Aerobic selectors in slaughterhouse activated sludge systems: a preliminary investigation. Bioresour. Technol. 100, 50–58. https://doi.org/10.1016/J. BIORTECH.2007.12.030. Al-Mutairi, N.Z., Al-Sharifi, F.A., Al-Shammari, S.B., 2008. Evaluation study of a slaughterhouse wastewater treatment plant including contact-assisted activated sludge and DAF. Desalination 225, 167–175. https://doi.org/10.1016/J.DESAL.2007.04.094. Amanatidou, E., Samiotis, G., Trikoilidou, E., Tzelios, D., Michailidis, A., 2016. Influence of wastewater treatment plants' operational conditions on activated sludge microbiological and morphological characteristics. Environ. Technol. 37, 265–278. https:// doi.org/10.1080/09593330.2015.1068379. Amani, T., Nosrati, M., Sreekrishnan, T.R., 2010. Anaerobic digestion from the viewpoint of microbiological, chemical, and operational aspects—a review. Environ. Rev. 18 (NA), 255–278. Andersen, D.R., Schmid, L.A., 1985. Pilot plant study of an anaerobic filter for treating wastes from a complex slaughterhouse. Proceedings of the… Industrial Waste Conference. Purdue University, USA. Appels, L., Baeyens, J., Degrève, J., Dewil, R., 2008. Principles and potential of the anaerobic digestion of waste-activated sludge. Prog. Energy Combust. Sci. 34 (6), 755–781. Armenante, P.M., Kafkewitz, D., Lewandowski, G.A., Jou, C.-J., 1999. Anaerobic–aerobic treatment of halogenated phenolic compounds. Water Res. 33, 681–692. https:// doi.org/10.1016/S0043-1354(98)00255-3. Arvanitoyannis, I.S., Ladas, D., 2008. Meat waste treatment methods and potential uses. Int. J. Food Sci. Technol. 43, 543–559. https://doi.org/10.1111/j.13652621.2006.01492.x. Avery, L.M., Killham, K., Jones, D.L., 2005. Survival of E. coli O157:H7 in organic wastes destined for land application. J. Appl. Microbiol. 98, 814–822. https://doi.org/10.1111/ j.1365-2672.2004.02524.x. Azad, H.S. (Ed.), 1976. Industrial Wastewater Management Handbook. McGraw – Hill Book Company, USA. Aziz, A., 2018. Biological Treatment of Slaughterhouse Wastewater Using Sequential Anaerobic and Aerobic SBR. Aligarh Muslim University, India. Banks, C., Wang, Z., 2004. Handbook of industrial and hazardous wastes treatment. Chapter 15: Treatment of Meat Wastes, second edition University of Southampton, Southampton, England. Bao, R., Yu, S., Shi, W., Zhang, X., Wang, Y., 2009. Aerobic granules formation and nutrients removal characteristics in sequencing batch airlift reactor (SBAR) at low temperature. J. Hazard. Mater. 168, 1334–1340. https://doi.org/10.1016/J. JHAZMAT.2009.03.020. Barber, W.P., Stuckey, D.C., 1999. The use of the anaerobic baffled reactor (ABR) for wastewater treatment: a review. Water Res. 33, 1559–1578. https://doi.org/10.1016/ S0043-1354(98)00371-6. Basitere, M., Williams, Y., Sheldon, M.S., Ntwampe, S.K.O., De Jager, D., Dlangamandla, C., 2016. Performance of an expanded granular sludge bed (EGSB) reactor coupled with anoxic and aerobic bioreactors for treating poultry slaughterhouse wastewater. Water Pract. Technol. 11, 86–92. https://doi.org/10.2166/wpt.2016.013. Bassin, J.P., Kleerebezem, R., Rosado, A.S., van Loosdrecht, M.C.M., Dezotti, M., 2012. Effect of different operational conditions on biofilm development, nitrification, and nitrifying microbial population in moving-bed biofilm reactors. Environ. Sci. Technol. 46, 1546–1555. https://doi.org/10.1021/es203356z. Bazrafshan, E., Kord Mostafapour, F., Farzadkia, M., Ownagh, K.A., Mahvi, A.H., 2012. Slaughterhouse wastewater treatment by combined chemical coagulation and electrocoagulation process. PLoS One 7, e40108. https://doi.org/10.1371/journal. pone.0040108. Belanger, D., Bergevin, P., Laperriere, J., Zaloum, R., 1986. Conception, contrOie et efficacite d'un reacteur biologique sequentiel pour I'epuration des eaux usees d'un abattoir. Sciences et techniques de I'eau 19, 142–156. Bernet, N., Delgenes, N., Akunna, J.C., Delgenes, J.P., Moletta, R., 2000. Combined anaerobic–aerobic SBR for the treatment of piggery wastewater. Water Res. 34, 611–619. https://doi.org/10.1016/S0043-1354(99)00170-0. Bertino, A., 2011. Study on One-stage Partial Nitritation-Anammox Process in Moving Bed Biofilm Reactors: A Sustainable Nitrogen Removal. Bicudo, J., Svoboda, I.F., 1995. Effect of intermittent-cycle extended-aeration treatment on the fate of carbonaceous material in pig slurry. Bioresour. Technol. 54, 53–62. Black, M.G., Brown, J.M., Kaye, E., 1974. Operational experiences with an abattoir waste digestion plant at Leeds. Water Pollution Control. Bohdziewicz, J., Sroka, E., Lobos, E., 2002. Application of the system which combines coagulation, activated sludge and reverse osmosis to the treatment of the wastewater produced by the meat industry. Desalination 144, 393–398. https://doi.org/ 10.1016/S0011-9164(02)00349-1. Bohm, J.-L., 1986. Digestion anaerobie des effluent d'slaughterhouses dans une unite pilote de 30 000 litres epuration et production d'energie. Entropie 130/131, 83–87. Boopathy, R., Bonvillain, C., Fontenot, Q., Kilgen, M., 2007. Biological treatment of low-salinity shrimp aquaculture wastewater using sequencing batch reactor. Int. Biodeterior. Biodegradation 59, 16–19. https://doi.org/10.1016/J. IBIOD.2006.05.003. Borja, R., Banks, C.J., Wang, Z., 1994. Performance and kinetics of an upflow anaerobic sludge blanket (UASB) reactor treating slaughterhouse wastewater. J. Environ. Sci. Heal. Part A Environ. Sci. Eng. Toxicol. 29, 2063–2085. https://doi.org/10.1080/ 10934529409376165. Borja, R., Banks, C.J., Martín, A., 1995a. Influence of the organic volumetric loading rate on soluble chemical oxygen demand removal in a down-flow fixed-bed reactor treating abattoir wastewater. J. Chem. Technol. Biotechnol. 64, 361–366. https://doi.org/ 10.1002/jctb.280640408. Borja, R., Banks, C.J., Wang, Z., 1995b. Effect of organic loading rate on anaerobic treatment of slaughterhouse wastewater in a fluidised-bed reactor. Bioresour. Technol. 52, 157–162. https://doi.org/10.1016/0960-8524(95)00017-9.

704

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

Borkar, R.P., Gulhane, M.L., Kotangale, A.J., 2013. Moving bed biofilm reactor–a new perspective in wastewater treatment. J. Environ. Sci. Toxicol. Food Technol. 6, 15–21. Bortone, G., Piccinini, S., 1991. Nitrification and denitrification in activated-sludge plants for pig slurry and wastewater from cheese dairies. Bioresour. Technol. 37, 243–252. https://doi.org/10.1016/0960-8524(91)90191-L. Bouallagui, H., Rachdi, B., Gannoun, H., Hamdi, M., 2009. Mesophilic and thermophilic anaerobic co-digestion of abattoir wastewater and fruit and vegetable waste in anaerobic sequencing batch reactors. Biodegradation 20, 401–409. https://doi.org/10.1007/ s10532-008-9231-1. Bull, M.A., Sterritt, R.M., Lester, J.N., 1982. The treatment of wastewaters from the meat industry: a review. Environ. Technol. Lett. 3, 117–126. https://doi.org/10.1080/ 09593338209384107. Bustillo-Lecompte, C.F., Mehrvar, M., 2015. Slaughterhouse wastewater characteristics, treatment, and management in the meat processing industry: a review on trends and advances. J. Environ. Manag. 161, 287–302. https://doi.org/10.1016/J. JENVMAN.2015.07.008. Bustillo-Lecompte, C.F., Mehrvar, M., 2017a. Slaughterhouse wastewater: treatment, management and resource recovery. Physico-chemical Wastewater Treatment and Resource Recovery. InTech https://doi.org/10.5772/65499. Bustillo-Lecompte, C.F., Mehrvar, M., 2017b. Treatment of actual slaughterhouse wastewater by combined anaerobic–aerobic processes for biogas generation and removal of organics and nutrients: an optimization study towards a cleaner production in the meat processing industry. J. Clean. Prod. 141, 278–289. https://doi.org/10.1016/ J.JCLEPRO.2016.09.060. Bustillo-Lecompte, C.F., Mehrvar, M., Quiñones-Bolaños, E., 2014. Cost-effectiveness analysis of TOC removal from slaughterhouse wastewater using combined anaerobic– aerobic and UV/H2O2 processes. J. Environ. Manag. 134, 145–152. https://doi.org/ 10.1016/J.JENVMAN.2013.12.035. Cabezas, A., Draper, P., Muxí, L., Etchebehere, C., 2006. Post-treatment of a slaughterhouse wastewater: stability of the microbial community of a sequencing batch reactor operated under oxygen limited conditions. Water Sci. Technol. 54 (2), 215–221. https://doi.org/10.2166/wst.2006.508. Cai, L., Zhang, T., 2013. Detecting human bacterial pathogens in wastewater treatment plants by a high-throughput shotgun sequencing technique. Environ. Sci. Technol. 47, 5433–5441. https://doi.org/10.1021/es400275r. Caixeta, C.E.T., Cammarota, M.C., Xavier, A.M.F., 2002. Slaughterhouse wastewater treatment: evaluation of a new three-phase separation system in a UASB reactor. Bioresour. Technol. 81, 61–69. https://doi.org/10.1016/S0960-8524(01)00070-0. Callaghan, F.J., Wase, D.A.J., Thayanithy, K., Forster, C.F., 2002. Continuous co-digestion of cattle slurry with fruit and vegetable wastes and chicken manure. Biomass Bioenergy 22, 71–77. https://doi.org/10.1016/S0961-9534(01)00057-5. Camp, W.W., Johnson, C.H., Tischler, L.F., Green, J.B., Gossett, R.E., 2001. Evaluation of moving bed biofilm reactor (MBBR) technology for the removal of volatile organic compounds. Proc. Water Environ. Fed. 2001, 74–87. https://doi.org/10.2175/ 193864701785019335. Campos, J.R., Foresti, E., Camacho, R.D.P., 1986. Anaerobic wastewater treatment in the food processing industry: two case studies. Water Sci. Technol. 18, 87–97. https:// doi.org/10.2166/wst.1986.0165. Campos, J.L., Garrido-Fernández, J.M., Méndez, R., Lema, J.M., 1999. Nitrification at high ammonia loading rates in an activated sludge unit. Bioresour. Technol. 68, 141–148. https://doi.org/10.1016/S0960-8524(98)00141-2. Cao, W., Mehrvar, M., 2011. Slaughterhouse wastewater treatment by combined anaerobic baffled reactor and UV/H2O2 processes. Chem. Eng. Res. Des. 89, 1136–1143. https://doi.org/10.1016/J.CHERD.2010.12.001. Cardinali-Rezende, J., Pereira, Z.L., Sanz, J.L., Chartone-Souza, E., Nascimento, A.M.A., 2012. Bacterial and archaeal phylogenetic diversity associated with swine sludge from an anaerobic treatment lagoon. World J. Microbiol. Biotechnol. 28, 3187–3195. https:// doi.org/10.1007/s11274-012-1129-8. Carreau, R., VanAcker, S., VanderZaag, A.C., Madani, A., Drizo, A., Jamieson, R., Gordon, R.J., 2012. Evaluation of a surface flow constructed wetland treating abattoir wastewater. Appl. Eng. Agric. 28, 757–766. Carvalho, P.N., Pirra, A., Basto, M.C.P., Almeida, C.M.R., 2013. Activated sludge systems removal efficiency of veterinary pharmaceuticals from slaughterhouse wastewater. Environ. Sci. Pollut. Res. 20, 8790–8800. https://doi.org/10.1007/ s11356-013-1867-7. Cassidy, D.P., Belia, E., 2005. Nitrogen and phosphorus removal from an abattoir wastewater in a SBR with aerobic granular sludge. Water Res. 39, 4817–4823. https://doi.org/ 10.1016/J.WATRES.2005.09.025. Castillo, A., llabres, P., Mata-Alvarez, J., 1999. A kinetic study of a combined anaerobic– aerobic system for treatment of domestic sewage. Water Res. 33, 1742–1747. https://doi.org/10.1016/S0043-1354(98)00405-9. Central Pollution Control Board of India, 2016. Slaughterhouse, meat and sea food industry. http://cpcb.nic.in/displaypdf.php?id= SW5kdXN0cnktU3BlY2lmaWMtU3RhbmRhcmRzL0VmZmx1ZW50LzQ0Mi0xLnBkZg==, Accessed date: 31 August 2018. Central Pollution Control Board of India, 2017. Revised comprehensive industry document on slaughterhouses. http:cpcb.nic.in/openpdffile.php?id= TGF0ZXN0RmlsZS8xNzVfMTUxMTI2NDE0MV9tZWRpYXBob3RvODkzOS5wZGY=, Accessed date: 09-08-2018. Chan, Y.J., Chong, M.F., Law, C.L., Hassell, D.G., 2009. A review on anaerobic–aerobic treatment of industrial and municipal wastewater. Chem. Eng. J. 155, 1–18. https://doi. org/10.1016/J.CEJ.2009.06.041. Chávez, P.C., Castillo, L.R., Dendooven, L., Escamilla-Silva, E.M., 2005. Poultry slaughter wastewater treatment with an up-flow anaerobic sludge blanket (UASB) reactor. Bioresour. Technol. 96, 1730–1736. https://doi.org/10.1016/J.BIORTECH.2004.08.017.

Chen, C.-K., Lo, S.-L., 2003. Treatment of slaughterhouse wastewater using an activated sludge/contact aeration process. Water Sci. Technol. 47, 285–292. https://doi.org/ 10.2166/wst.2003.0658. Chen, Y., Cheng, J.J., Creamer, K.S., 2008. Inhibition of anaerobic digestion process: a review. Bioresour. Technol. 99, 4044–4064. https://doi.org/10.1016/J. BIORTECH.2007.01.057. Chernicharo, C.A.L., 2006. Post-treatment options for the anaerobic treatment of domestic wastewater. Rev. Environ. Sci. Bio/Technology 5, 73–92. https://doi.org/10.1007/ s11157-005-5683-5. Chittenden, J.A., Wells Jr., W.J., 1971. Rotating biological contactors following anaerobic lagoons. J. (Water Pollut. Control FEd.) 746–754. Chiu, Y.-C., Lee, L.-L., Chang, C.-N., Chao, A.C., 2007. Control of carbon and ammonium ratio for simultaneous nitrification and denitrification in a sequencing batch bioreactor. Int. Biodeterior. Biodegradation 59, 1–7. https://doi.org/10.1016/J. IBIOD.2006.08.001. Choi, Y.S., Hong, S.W., Kim, S.J., Chung, I.H., 2002. Development of a biological process for livestock wastewater treatment using a technique for predominant outgrowth of Bacillus species. Water Sci. Technol. 45 (12), 71–78. Coimbra-Araújo, C.H., Mariane, L., Júnior, C.B., Frigo, E.P., Frigo, M.S., Araújo, I.R.C., Alves, H.J., 2014. Brazilian case study for biogas energy: production of electric power, heat and automotive energy in condominiums of agroenergy. Renew. Sust. Energ. Rev. 40, 826–839. https://doi.org/10.1016/J.RSER.2014.07.024. Colic, M., Morse, W., Lechter, A., Hicks, J., Holley, S., Mattia, C., 2008. Enabling the performance of the MBBR installed to treat meat processing wastewater. Proc. Water Environ. Fed. 2008, 3358–3374. https://doi.org/10.2175/ 193864708788733378. Cuetos, M.J., Gómez, X., Otero, M., Morán, A., 2008. Anaerobic digestion of solid slaughterhouse waste (SHW) at laboratory scale: influence of co-digestion with the organic fraction of municipal solid waste (OFMSW). Biochem. Eng. J. 40, 99–106. https:// doi.org/10.1016/J.BEJ.2007.11.019. Dague, R.R., 1993. Anaerobic sequencing batch reactor. U.S. Patent 5,185,079. https:// patentimages.storage.googleapis.com/e6/d9/2d/3c1360fa67ae16/US5185079.pdf Dague, R.R., Urell, R.F., Krieger, E.R., 1990. Treatment of pork processing wastewater in a covered anaerobic lagoon with gas recovery. Proceedings of the Industrial Waste Conference. Purdue University, USA. Dague, R.R., Banik, G.C., Ellis, T.G., 1998. Anaerobic sequencing batch reactor treatment of dilute wastewater at psychrophilic temperatures. Water Environ. Res. 70, 155–160. https://doi.org/10.2175/106143098X126991. Daigger, G.T., Boltz, J.P., 2011. Trickling filter and trickling filter-suspended growth process design and operation: a state-of-the-art review. Water Environ. Res. 83, 388–404. https://doi.org/10.2175/106143010X12681059117210. De Kreuk, M.K., Heijnen, J.J., van Loosdrecht, M.C.M., 2005. Simultaneous COD, nitrogen, and phosphate removal by aerobic granular sludge. Biotechnol. Bioeng. 90, 761–769. https://doi.org/10.1002/bit.20470. De Nardi, I.R., Del Nery, V., Amorim, A.K.B., dos Santos, N.G., Chimenes, F., 2011. Performances of SBR, chemical–DAF and UV disinfection for poultry slaughterhouse wastewater reclamation. Desalination 269, 184–189. https://doi.org/10.1016/J. DESAL.2010.10.060. De Villiers, G.H., Pretorius, W.A., 2001. Abattoir effluent treatment and protein production. Water Sci. Technol. 43, 243–250. Debik, E., Coskun, T., 2009. Use of the Static Granular Bed Reactor (SGBR) with anaerobic sludge to treat poultry slaughterhouse wastewater and kinetic modeling. Bioresour. Technol. 100, 2777–2782. https://doi.org/10.1016/J.BIORTECH.2008.12.058. Del Nery, V., Damianovic, M.H.Z., Barros, F.G., 2001. The use of upflow anaerobic sludge blanket reactors in the treatment of poultry slaughterhouse wastewater. Water Sci. Technol. 44, 83–88. https://doi.org/10.2166/wst.2001.0185. Del Nery, V., de Nardi, I.R., Damianovic, M.H.R.Z., Pozzi, E., Amorim, A.K.B., Zaiat, M., 2007. Long-term operating performance of a poultry slaughterhouse wastewater treatment plant. Resour. Conserv. Recycl. 50, 102–114. https://doi.org/10.1016/J. RESCONREC.2006.06.001. Del Nery, V., Pozzi, E., Damianovic, M.H.R.Z., Domingues, M.R., Zaiat, M., 2008. Granules characteristics in the vertical profile of a full-scale upflow anaerobic sludge blanket reactor treating poultry slaughterhouse wastewater. Bioresour. Technol. 99, 2018–2024. https://doi.org/10.1016/J.BIORTECH.2007.03.019. Del Nery, V., Damianovic, M.H.Z., Pozzi, E., de Nardi, I.R., Caldas, V.E.A., Pires, E.C., 2013. Long-term performance and operational strategies of a poultry slaughterhouse waste stabilization pond system in a tropical climate. Resour. Conserv. Recycl. 71, 7–14. https://doi.org/10.1016/J.RESCONREC.2012.11.006. Del Nery, V., Damianovic, M.H.Z., Moura, R.B., Pozzi, E., Pires, E.C., Foresti, E., 2016. Poultry slaughterhouse wastewater treatment plant for high quality effluent. Water Sci. Technol. 73, 309–316. https://doi.org/10.2166/wst.2015.494. Del Pozo, R., Diez, V., 2005. Integrated anaerobic–aerobic fixed-film reactor for slaughterhouse wastewater treatment. Water Res. 39, 1114–1122. https://doi.org/10.1016/J. WATRES.2005.01.013. Del Pozo, R., Diez, V., Beltrán, S., 2000. Anaerobic pre-treatment of slaughterhouse wastewater using fixed-film reactors. Bioresour. Technol. 71, 143–149. https://doi.org/ 10.1016/S0960-8524(99)90065-2. Delforno, T.P., Lacerda Júnior, G.V., Noronha, M.F., Sakamoto, I.K., Varesche, M.B.A., Oliveira, V.M., 2017. Microbial diversity of a full-scale UASB reactor applied to poultry slaughterhouse wastewater treatment: integration of 16S rRNA gene amplicon and shotgun metagenomic sequencing. Microbiologyopen 6, e00443. https://doi.org/ 10.1002/mbo3.443. Demirel, B., Scherer, P., 2008. The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of biomass to methane: a review. Rev. Environ. Sci. Bio/Technology 7, 173–190. https://doi.org/10.1007/s11157008-9131-1.

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708 Demirel, B., Yenigun, O., Onay, T.T., 2005. Anaerobic treatment of dairy wastewaters: a review. Process Biochem. 40, 2583–2595. https://doi.org/10.1016/J. PROCBIO.2004.12.015. El-Mashad, H.M., Zeeman, G., Van Loon, W.K., Bot, G.P., Lettinga, G., 2004. Effect of temperature and temperature fluctuation on thermophilic anaerobic digestion of cattle manure. Bioresour. Technol. 95 (2), 191–201. Evans, R.A., Cromar, N.J., Fallowfield, H.J., 2005. Performance of a pilot-scale high rate algal pond system treating abattoir wastewater in rural South Australia: nitrification and denitrification. Water Sci. Technol. 51, 117–124. Fantozzi, F., Buratti, C., 2009. Biogas production from different substrates in an experimental Continuously Stirred Tank Reactor anaerobic digester. Bioresour. Technol. 100, 5783–5789. https://doi.org/10.1016/J.BIORTECH.2009.06.013. Farooqi, I.H., Asifuzzaman, Basheer, F., 2009. Treatment of slaughterhouse waste by an anaerobic hybrid reactor. Asian J. Water, Environ. Pollut. 6, 93–97. Festino, C., Aubart, C., 1986. Épuration d'effluents liquides et valorisation énergétique de déchets solides d'abattoir par voie anaérobie. Entropie 130, 57–67. Filali-Meknassi, Y., Auriol, M., Tyagi, R.D., Comeau, Y., Surampalli, R.Y., 2005a. Phosphorus co-precipitation in the biological treatment of slaughterhouse wastewater in a sequencing batch reactor. Pract. Period. Hazardous, Toxic, Radioact. Waste Manag 9, 179–192. https://doi.org/10.1061/(ASCE)1090-025X(2005)9:3(179). Filali-Meknassi, Y., Auriol, M., Tyagi, R.D., Comeau, Y., Surampalli, R.Y., 2005b. Design strategy for a simultaneous nitrification/denitrification of a slaughterhouse wastewater in a sequencing batch reactor: ASM2D modeling and verification. Environ. Technol. 26, 1081–1100. https://doi.org/10.1080/ 09593332608618478. Fongsatitkul, P., Elefsiniotis, P., Yamasmit, A., Yamasmit, N., 2004. Use of sequencing batch reactors and Fenton's reagent to treat a wastewater from a textile industry. Biochem. Eng. J. 21 (3), 213–220. Fongsatitkul, P., Wareham, D.G., Elefsiniotis, P., Charoensuk, P., 2011. Treatment of a slaughterhouse wastewater: effect of internal recycle rate on chemical oxygen demand, total Kjeldahl nitrogen and total phosphorus removal. Environ. Technol. 32, 1755–1759. https://doi.org/10.1080/09593330.2011.555421. Food and Agriculture Organization of the United Nations, 2018. Meat Market Review. http://www.fao.org/3/I9286EN/i9286en.pdf, Accessed date: 27 September 2018. Francioso, O., Rodriguez-Estrada, M.T., Montecchio, D., Salomoni, C., Caputo, A., Palenzona, D., 2010. Chemical characterization of municipal wastewater sludges produced by two-phase anaerobic digestion for biogas production. J. Hazard. Mater. 175 (1–3), 740–746. Fuchs, W., Binder, H., Mavrias, G., Braun, R., 2003. Anaerobic treatment of wastewater with high organic content using a stirred tank reactor coupled with a membrane filtration unit. Water Res. 37, 902–908. https://doi.org/10.1016/S00431354(02)00246-4. Gallert, C., Winter, J., 1997. Mesophilic and thermophilic anaerobic digestion of sourcesorted organic wastes: effect of ammonia on glucose degradation and methane production. Appl. Microbiol. Biotechnol. 48, 405–410. https://doi.org/10.1007/ s002530051071. Gannoun, H., Bouallagui, H., Okbi, A., Sayadi, S., Hamdi, M., 2009. Mesophilic and thermophilic anaerobic digestion of biologically pretreated abattoir wastewaters in an upflow anaerobic filter. J. Hazard. Mater. 170, 263–271. https://doi.org/10.1016/J. JHAZMAT.2009.04.111. Gannoun, H., Khelifi, E., Omri, I., Jabari, L., Fardeau, M.L., Bouallagui, H., Godon, J.J., Hamdi, M., 2013. Microbial monitoring by molecular tools of an upflow anaerobic filter treating abattoir wastewaters. Bioresour. Technol. 142, 269–277. Gao, D., Liu, L., Liang, H., Wu, W.-M., 2011. Aerobic granular sludge: characterization, mechanism of granulation and application to wastewater treatment. Crit. Rev. Biotechnol. 31, 137–152. https://doi.org/10.3109/07388551.2010.497961. Gariépy, S., Tyagi, R.D., Couillard, D., Tran, F., 1989. Thermophilic process for protein recovery as an alternative to slaughterhouse wastewater treatment. Biol. Wastes 29, 93–105. https://doi.org/10.1016/0269-7483(89)90090-6. Gasiunas, V., Strusevicius, Z., Struseviciene, M.-S., 2005. Pollutant removal by horizontal subsurface flow constructed wetlands in Lithuania. J. Environ. Sci. Heal. Part A 40, 1467–1478. https://doi.org/10.1081/ESE-200055889. Gerardi, M.H., 2003. Nitrification and Denitrification in the Activated Sludge Process. John Wiley & Sons. Gerbens-Leenes, P.W., Mekonnen, M.M., 2013. The water footprint of poultry, pork and beef: a comparative study in different countries and production systems. Water Resour. Ind. 1–2, 25–36. https://doi.org/10.1016/J.WRI.2013.03.001. Granada, C.E., Hasan, C., Marder, M., Konrad, O., Vargas, L.K., Passaglia, L.M., Giongo, A., de Oliveira, R.R., Pereira, L.D.M., de Jesus Trindade, F., Sperotto, R.A., 2018. Biogas from slaughterhouse wastewater anaerobic digestion is driven by the archaeal family Methanobacteriaceae and bacterial families Porphyromonadaceae and Tissierellaceae. Renew. Energy 118, 840–846. Gutiérrez-Sarabia, A., Fernández-Villagómez, G., Martínez-Pereda, P., Rinderknecht-Seijas, N., Poggi-Varaldo, H.M., 2004. Slaughterhouse wastewater treatment in a full-scale system with constructed wetlands. Water Environ. Res. 76, 334–343. https://doi. org/10.2175/106143004X141924. Hai, R., He, Y., Wang, X., Li, Y., 2015. Simultaneous removal of nitrogen and phosphorus from swine wastewater in a sequencing batch biofilm reactor. Chinese J. Chem. Eng. 23, 303–308. https://doi.org/10.1016/J.CJCHE.2014.09.036. Hamawand, I., Baillie, C., Hamawand, I., Baillie, C., 2015. Anaerobic digestion and biogas potential: simulation of lab and industrial-scale processes. Energies 8, 454–474. https://doi.org/10.3390/en8010454. Hammer, M.J., Jacobsen, D., 1970. Anaerobic Lagoon Treatment of Packinghouse Waste Water. Handous, N., Gannoun, H., Hamdi, M., Bouallagui, H., 2017. Two-stage anaerobic digestion of meat processing solid wastes: methane potential improvement with wastewater

705

addition and solid substrate fermentation. Waste and Biomass Valorization 0, 3. https://doi.org/10.1007/s12649-017-0055-2. Hansen, C.L., West, G.T., 1992. Anaerobic digestion of rendering waste in an upflow anaerobic sludge blanket digester. Bioresour. Technol. 41, 181–185. https://doi.org/ 10.1016/0960-8524(92)90190-9. Harrison, J.T., Viraraghavan, T., Sommerstad, H., 1991. Treatment of slaughterhouse effluent using an anaerobic filter. Can. J. Civ. Eng. 18, 436–445. https://doi.org/10.1139/ l91-054. Hassard, F., Biddle, J., Cartmell, E., Jefferson, B., Tyrrel, S., Stephenson, T., 2015. Rotating biological contactors for wastewater treatment – a review. Process. Saf. Environ. Prot. 94, 285–306. https://doi.org/10.1016/J.PSEP.2014.07.003. He, Y., Xu, P., Li, C., Zhang, B., 2005. High-concentration food wastewater treatment by an anaerobic membrane bioreactor. Water Res. 39, 4110–4118. https://doi.org/10.1016/ J.WATRES.2005.07.030. He, Q., Song, Q., Zhang, S., Zhang, W., Wang, H., 2018. Simultaneous nitrification, denitrification and phosphorus removal in an aerobic granular sequencing batch reactor with mixed carbon sources: reactor performance, extracellular polymeric substances and microbial successions. Chem. Eng. J. 331, 841–849. https://doi.org/10.1016/J. CEJ.2017.09.060. Heddle, J.F., 1979. Activated sludge treatment of slaughterhouse wastes with protein recovery. Water Res. 13, 581–584. Hernández, D., Riaño, B., Coca, M., Solana, M., Bertucco, A., García-González, M.C., 2016. Microalgae cultivation in high rate algal ponds using slaughterhouse wastewater for biofuel applications. Chem. Eng. J. 285, 449–458. https://doi.org/10.1016/J. CEJ.2015.09.072. Hopwood, D., 1977. Effluent treatment in meat and poultry processing industries. Process Biochem. 12, 5–8. Hosseini, S.H., Borghei, S.M., 2005. The treatment of phenolic wastewater using a moving bed bio-reactor. Process Biochem. 40, 1027–1031. https://doi.org/10.1016/J. PROCBIO.2004.05.002. Hsiao, T.-H., Huang, J.-S., Huang, Y.-I., 2012. Process kinetics of an activated-sludge reactor system treating poultry slaughterhouse wastewater. Environ. Technol. 33, 829–835. https://doi.org/10.1080/09593330.2011.597782. Husain, A., 1998. Mathematical models of the kinetics of anaerobic digestion—a selected review. Biomass Bioenergy 14, 561–571. https://doi.org/10.1016/S0961-9534(97) 10047-2. Hwu, C.-S., Tseng, S.-K., Yuan, C.-Y., Kulik, Z., Lettinga, G., 1998. Biosorption of long-chain fatty acids in UASB treatment process. Water Res. 32, 1571–1579. https://doi.org/ 10.1016/S0043-1354(97)00352-7. Işik, M., Sponza, D.T., 2004. Anaerobic/aerobic sequential treatment of a cotton textile mill wastewater. J. Chem. Technol. Biotechnol. 79, 1268–1274. https://doi.org/10.1002/ jctb.1122. Işik, M., Sponza, D.T., 2006. Biological treatment of acid dyeing wastewater using a sequential anaerobic/aerobic reactor system. Enzym. Microb. Technol. 38, 887–892. https://doi.org/10.1016/J.ENZMICTEC.2005.05.018. Jabari, L., Gannoun, H., Khelifi, E., Cayol, J.L., Godon, J.J., Hamdi, M., Fardeau, M.L., 2016. Bacterial ecology of abattoir wastewater treated by an anaerobic digestor. Braz. J. Microbiol. 47 (1), 73–84. Jensen, P.D., Yap, S.D., Boyle-Gotla, A., Janoschka, J., Carney, C., Pidou, M., Batstone, D.J., 2015. Anaerobic membrane bioreactors enable high rate treatment of slaughterhouse wastewater. Biochem. Eng. J. 97, 132–141. https://doi.org/ 10.1016/J.BEJ.2015.02.009. Johns, M.R., 1995. Developments in wastewater treatment in the meat processing industry: a review. Bioresour. Technol. 54, 203–216. https://doi.org/10.1016/0960-8524 (95)00140-9. Johnson, D.B., Krill, W.P., 1976. Proc. 31st Ind. Waste Conf., Purdue Univ. pp. 733–742. Joslin, B.J., Farrar, J., 2005. Full scale results from slaughterhouse wastewater treatment in a moving bed biofilm reactor. Proc. Water Environ. Fed. 2005, 1787–1795. https://doi. org/10.2175/193864705783867062. Joss, A., Andersen, H., Ternes, T., Richle, P.R., Siegrist, H., 2004. Removal of estrogens in municipal wastewater treatment under aerobic and anaerobic conditions: consequences for plant optimization. Environ. Sci. Technol. 38, 3047–3055. Keller, J., Subramaniam, K., Gösswein, J., Greenfield, P.F., 1997. Nutrient removal from industrial wastewater using single tank sequencing batch reactors. Water Sci. Technol. 35, 137–144. https://doi.org/10.1016/S0273-1223(97)00104-2. Kermani, M., Bina, B., Movahedian, H., Amin, M.M., Nikaeen, M., 2009. Biological phosphorus and nitrogen removal from wastewater using moving bed biofilm process. Iran. J. Biotechnol. 7, 19–27. Khursheed, A., Gaur, R.Z., Sharma, M.K., Tyagi, V.K., Khan, A.A., Kazmi, A.A., 2018. Dependence of enhanced biological nitrogen removal on carbon to nitrogen and rbCOD to sbCOD ratios during sewage treatment in sequencing batch reactor. J. Clean. Prod. 171, 1244–1254. https://doi.org/10.1016/J.JCLEPRO.2017.10.055. Kishida, N., Tsuneda, S., Kim, J.H., Sudo, R., 2009. Simultaneous nitrogen and phosphorus removal from high-strength industrial wastewater using aerobic granular sludge. J. Environ. Eng. 135, 153–158. https://doi.org/10.1061/(ASCE)0733-9372(2009)135: 3(153). Kondusamy, D., Kalamdhad, A.S., 2014. Pre-treatment and anaerobic digestion of food waste for high rate methane production – a review. J. Environ. Chem. Eng. 2, 1821–1830. https://doi.org/10.1016/J.JECE.2014.07.024. Kostyshyn, C.R., Bonkonski, W.A., Sointio, J.E., 1988. Anaerobic treatment of a beef processing plant wastewater: a case history. Proceedings of the Industrial Waste Conference. Purdue University, USA. Kuglarz, M., Mrowiec, B., Bohdziewicz, J., 2011. Influence of kitchen biowaste addition on the effectiveness of animal manure digestion in continuous condition. Research and Application of New Technologies in Wastewater Treatment and Municipal Solid Waste Disposal in Ukraine, Sweden and Poland.

706

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

Kundu, P., Debsarkar, A., Mukherjee, S., 2013. Treatment of slaughter house wastewater in a sequencing batch reactor: performance evaluation and biodegradation kinetics. Biomed. Res. Int. 2013, 134872. https://doi.org/10.1155/2013/134872. Lemaire, R., Marcelino, M., Yuan, Z., 2008a. Achieving the nitrite pathway using aeration phase length control and step-feed in an SBR removing nutrients from abattoir wastewater. Biotechnol. Bioeng. 100, 1228–1236. https://doi.org/10.1002/bit.21844. Lemaire, R., Yuan, Z., Blackall, L.L., Crocetti, G.R., 2008b. Microbial distribution of Accumulibacter spp. and Competibacter spp. in aerobic granules from a lab-scale biological nutrient removal system. Environ. Microbiol. 10, 354–363. https://doi.org/ 10.1111/j.1462-2920.2007.01456.x. Lemaire, R., Yuan, Z., Bernet, N., Marcos, M., Yilmaz, G., Keller, J., 2009. A sequencing batch reactor system for high-level biological nitrogen and phosphorus removal from abattoir wastewater. Biodegradation 20 (3), 339–350. León-Becerril, E., García-Camacho, J.E., Del Real-Olvera, J., López-López, A., 2016. Performance of an upflow anaerobic filter in the treatment of cold meat industry wastewater. Process. Saf. Environ. Prot. 102, 385–391. https://doi.org/10.1016/ J.PSEP.2016.04.016. Li, C.T., Hwu, N.T., Whang, J.S., 1984. Treatment of slaughterhouse wastewater by biofiltration tower. Proceedings of the 2nd International Conference on Fixed-film Biological Processes. US Army Corps Engineering Construction Engineering Research Laboratory, Champaign, Ill. Li, J., Healy, M.G., Zhan, X., Norton, D., Rodgers, M., 2008a. Effect of aeration rate on nutrient removal from slaughterhouse wastewater in intermittently aerated sequencing batch reactors. Water Air Soil Pollut. 192, 251–261. https://doi.org/10.1007/s11270008-9652-9. Li, J.P., Healy, M.G., Zhan, X.M., Rodgers, M., 2008b. Nutrient removal from slaughterhouse wastewater in an intermittently aerated sequencing batch reactor. Bioresour. Technol. 99, 7644–7650. https://doi.org/10.1016/J.BIORTECH.2008.02.001. Li, J., Elliott, D., Nielsen, M., Healy, M.G., Zhan, X., 2011. Long-term partial nitrification in an intermittently aerated sequencing batch reactor (SBR) treating ammonium-rich wastewater under controlled oxygen-limited conditions. Biochem. Eng. J. 55, 215–222. https://doi.org/10.1016/J.BEJ.2011.05.002. Li, Y., Zhang, R., He, Y., Zhang, C., Liu, X., Chen, C., Liu, G., 2014. Anaerobic co-digestion of chicken manure and corn stover in batch and continuously stirred tank reactor (CSTR). Bioresour. Technol. 156, 342–347. Li, Y., Chen, Y., Wu, J., 2019. Enhancement of methane production in anaerobic digestion process: a review. Appl. Energy 240, 120–137. Liu, Y., 2010. Taxonomy of methanogens. Handbook of Hydrocarbon and Lipid Microbiology, pp. 547–558. Liu, Y., Kang, X., Li, X., Yuan, Y., 2015. Performance of aerobic granular sludge in a sequencing batch bioreactor for slaughterhouse wastewater treatment. Bioresour. Technol. 190, 487–491. https://doi.org/10.1016/J.BIORTECH.2015.03.008. López-López, A., Vallejo-Rodríguez, R., Méndez-Romero, D.C., 2010. Evaluation of a combined anaerobic and aerobic system for the treatment of slaughterhouse wastewater. Environ. Technol. 31, 319–326. https://doi.org/10.1080/09593330903470693. Louvet, J.N., Homeky, B., Casellas, M., Pons, M.N., Dagot, C., 2013. Monitoring of slaughterhouse wastewater biodegradation in a SBR using fluorescence and UV–Visible absorbance. Chemosphere 91, 648–655. https://doi.org/10.1016/J. CHEMOSPHERE.2013.01.011. Lovett, D.A., Travers, S.M., Davey, K.R., 1984. Activated sludge treatment of abattoir wastewater—I: Influence of sludge age and feeding pattern. Water Res. 18, 429–434. Mace, S., Mata-Alvarez, J., 2002. Utilization of SBR technology for wastewater treatment: an overview. Ind. Eng. Chem. Res. 41, 5539–5553. https://doi.org/ 10.1021/ie0201821. Manjunath, N.T., Mehrotra, I., Mathur, R.P., 2000. Treatment of wastewater from slaughterhouse by DAF-UASB system. Water Res. 34, 1930–1936. https://doi.org/10.1016/ S0043-1354(99)00337-1. Mannina, G., Capodici, M., Cosenza, A., Trapani, D. Di, 2016. Removal of Carbon and Nutrients From Wastewater in a Moving Bed Membrane Biofilm Reactor: The Influence of the Sludge Retention Time. Mao, C., Feng, Y., Wang, X., Ren, G., 2015. Review on research achievements of biogas from anaerobic digestion. Renew. Sust. Energ. Rev. 45, 540–555. https://doi.org/10.1016/J. RSER.2015.02.032. Marcinkowski, M., Hansen, J.A., Poulsen, T.G., 2004. Application of Nitritation and Denitritation Process in Treatment of Cattle Slaughterhouse Wastewater. Aalborg Universitet. Marcos, A., Al-Kassir, A., Mohamad, A.A., Cuadros, F., López-Rodríguez, F., 2010. Combustible gas production (methane) and biodegradation of solid and liquid mixtures of meat industry wastes. Appl. Energy 87, 1729–1735. https://doi.org/10.1016/J. APENERGY.2009.09.037. Marcos, A., Al-Kassir, A., López, F., Cuadros, F., Brito, P., 2012. Environmental treatment of slaughterhouse wastes in a continuously stirred anaerobic reactor: effect of flow rate variation on biogas production. Fuel Process. Technol. 103, 178–182. https://doi.org/ 10.1016/J.FUPROC.2011.12.035. Martínez, J., Borzacconi, L., Mallo, M., Galisteo, M., Viñas, M., 1995a. Treatment of slaughterhouse wastewater. Water Sci. Technol. 32, 99–104. https://doi.org/10.1016/02731223(96)00143-6. Martínez, J., Borzacconi, L., Mallo, M., Galisteo, M., Viñas, M., 1995b. Treatment of slaughterhouse wastewater. Water Sci. Technol. 32, 99–104. https://doi.org/10.1016/02731223(96)00143-6. Martins das Neves, L.C., Converti, A., Vessoni Penna, T.C., 2009. Biogas production: new trends for alternative energy sources in rural and urban zones. Chem. Eng. Technol. 32, 1147–1153. https://doi.org/10.1002/ceat.200900051. Massé, D.I., Croteau, F., 1999. Low temperature anaerobic treatment of swine manure slurry under Canadian climatic conditions. Proceedings of the Second International Symposium on Anaerobic Digestion of Solid Waste, pp. 176–179.

Massé, D.I., Masse, L., 2000a. Characterization of wastewater from hog slaughterhouses in Eastern Canada and evaluation of their in-plant wastewater treatment systems. Can. Agric. Eng. 42, 139–146. Massé, D.I., Masse, L., 2000b. Treatment of slaughterhouse wastewater in anaerobic sequencing batch reactors, Agriculture and Agri-Food Canada contribution no. 659. Can. Agric. Eng. 42, 131. Massé, D.I., Masse, L., 2001. The effect of temperature on slaughterhouse wastewater treatment in anaerobic sequencing batch reactors. Bioresour. Technol. 76, 91–98. https://doi.org/10.1016/S0960-8524(00)00105-X. Masse, L., Massé, D.I., 2005. Effect of soluble organic, particulate organic, and hydraulic shock loads on anaerobic sequencing batch reactors treating slaughterhouse wastewater at 20 °C. Process Biochem. 40, 1225–1232. https://doi.org/10.1016/J. PROCBIO.2004.04.012. Massé, D.I., Masse, L., Bourgeois, N., 1999. Anaerobic processing of slaughterhouse wastewater in a SBR. Proceedings of the 8th International Conference on Management Strategies for Organic Waste in Agriculture. 1, p. 375. Massé, D.I., Masse, L., Verville, A., Bilodeau, S., 2001. The start-up of anaerobic sequencing batch reactors at 20 °C and 25 °C for the treatment of slaughterhouse wastewater. J. Chem. Technol. Biotechnol. 76, 393–400. https://doi.org/ 10.1002/jctb.395. Masse, L., Kennedy, K., Chou, S., 2001. Testing of alkaline and enzymatic hydrolysis pretreatments for fat particles in slaughterhouse wastewater. Bioresour. Technol. 77, 145–155. https://doi.org/10.1016/S0960-8524(00)00146-2. McCabe, B.K., Hamawand, I., Harris, P., Baillie, C., Yusaf, T., 2014. A case study for biogas generation from covered anaerobic ponds treating abattoir wastewater: investigation of pond performance and potential biogas production. Appl. Energy 114, 798–808. https://doi.org/10.1016/J.APENERGY.2013.10.020. Mees, J.B.R., Gomes, S.D., Vilas Boas, M.A., Gomes, B.M., Passig, F.H., 2011. Kinetic behavior of nitrification in the post-treatment of poultry wastewater in a sequential batch reactor. Eng. Agrícola 31, 954–964. https://doi.org/10.1590/S010069162011000500013. Mees, J.B.R., Gomes, S.D., Hasan, S.D.M., Gomes, B.M., Vilas Boas, M.A., 2014. Nitrogen removal in a SBR operated with and without pre-denitrification: effect of the carbon:nitrogen ratio and the cycle time. Environ. Technol. 35, 115–123. https://doi.org/ 10.1080/09593330.2013.816373. Mekonnen, M.M., Hoekstra, A.Y., 2012. A global assessment of the water footprint of farm animal products. Ecosystems 15, 401–415. https://doi.org/10.1007/s10021-0119517-8. Merzouki, M., Bernet, N., Delgenès, J.P., Benlemlih, M., 2005. Effect of prefermentation on denitrifying phosphorus removal in slaughterhouse wastewater. Bioresour. Technol. 96, 1317–1322. https://doi.org/10.1016/J.BIORTECH.2004.11.017. Metzner, G., Temper, U., 1990. Operation and optimization of a full-scale fixed-bed reactor for anaerobic digestion of animal rendering waste water. Water Sci. Technol. 22, 373–384. https://doi.org/10.2166/wst.1990.0162. Miranda, L.A.S., Henriques, J.A.P., Monteggia, L.O., 2005. A full-scale UASB reactor for treatment of pig and cattle slaughterhouse wastewater with a high oil and grease content. Brazilian J. Chem. Eng. 22, 601–610. https://doi.org/10.1590/ S0104-66322005000400013. Mittal, G.S., 2006. Treatment of wastewater from abattoirs before land application—a review. Bioresour. Technol. 97, 1119–1135. https://doi.org/10.1016/J. BIORTECH.2004.11.021. Moestedt, J., Nordell, E., Yekta, S.S., Lundgren, J., Martí, M., Sundberg, C., Ejlertsson, J., Svensson, B.H., Björn, A., 2016. Effects of trace element addition on process stability during anaerobic co-digestion of OFMSW and slaughterhouse waste. Waste Manag. 47, 11–20. Monclús, H., Sipma, J., Ferrero, G., Rodriguez-Roda, I., Comas, J., 2010. Biological nutrient removal in an MBR treating municipal wastewater with special focus on biological phosphorus removal. Bioresour. Technol. 101 (11), 3984–3991. Moodie, S.P., Greenfield, P.F., 1978. Treatment of abattoir effluent by trickling filtration. J. (Water Pollut. Control FEd.) 2741–2751. Morita, M., Malvankar, N.S., Franks, A.E., Summers, Z.M., Giloteaux, L., Rotaru, A.E., Rotaru, C., Lovley, D.R., 2011. Potential for direct interspecies electron transfer in methanogenic wastewater digester aggregates. MBio 2 (4), e00159-11. Mun, Y.W., 2012. Production of Methane From Palm Oil Mill Effluent by Using Ultrasonicated Membrane Anaerobic System (UMAS). Munir Baddour, E., Farhoud, N., Sharholy, M., Mohammed, I., Magid, A., 2016. Biological treatment of poultry slaughterhouses wastewater by using aerobic moving bed biofilm reactor. Int. Res. J. Public Environ. Heal. 3, 96–106. https://doi.org/10.15739/ irjpeh.16.013. Mutua, D.N., Mwaniki Njagi, E.N., 2016. Biological treatment of meat processing wastewater using lab-scale anaerobic-aerobic/anoxic sequencing batch reactors operated in series. J. Bioremediation Biodegrad. 7. https://doi.org/10.4172/21556199.1000362. Mutua, D.N., Mwaniki Njagi, E.N., Orinda, G., Obondi, G., Kansiime, F., Kyambadde, J., Omara, J., Odong, R., Butungi, H., 2016. Biological treatment of meat processing wastewater using lab-scale anaerobic-aerobic/anoxic sequencing batch reactors operated in series. J. Bioremediation Biodegrad. 7, 1–6. https://doi.org/10.4172/21556199.1000362. Myra, T., David, H., Judith, T., Marina, Y., Ricky, B.J., Reynaldo, E., 2015. Biological treatment of meat processing wastewater using anaerobic sequencing batch reactor (ASBR). International Research Journal of Biological Sciences 4, 66–75. Nachaiyasit, S., Stuckey, D.C., 1997. Effect of low temperatures on the performance of an anaerobic baffled reactor (ABR). J. Chem. Technol. Biotechnol. 69, 276–284. https://doi.org/10.1002/(SICI)1097-4660(199706)69:2b276::AID-JCTB711N3.0. CO;2-T.

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708 Nacheva, P.M., Pantoja, M.R., Serrano, E.A.L., 2011. Treatment of slaughterhouse wastewater in upflow anaerobic sludge blanket reactor. Water Sci. Technol. 63, 877–884. https://doi.org/10.2166/wst.2011.265. Najafpour, G., Yieng, H.A., Younesi, H., Zinatizadeh, A., 2005. Effect of organic loading on performance of rotating biological contactors using Palm Oil Mill effluents. Process Biochem. 40, 2879–2884. https://doi.org/10.1016/J.PROCBIO.2005.01.002. Nancharaiah, Y.V., Venkata Mohan, S., Lens, P.N.L., 2016. Recent advances in nutrient removal and recovery in biological and bioelectrochemical systems. Bioresour. Technol. 215, 173–185. https://doi.org/10.1016/J.BIORTECH.2016.03.129. Nandy, T., Kaul, S.N., 2001. Anaerobic pre-treatment of herbal-based pharmaceutical wastewater using fixed-film reactor with recourse to energy recovery. Water Res. 35 (2), 351–362. Ndegwa, P.M., Hamilton, D.W., Lalman, J.A., Cumba, H.J., 2008. Effects of cycle-frequency and temperature on the performance of anaerobic sequencing batch reactors (ASBRs) treating swine waste. Bioresour. Technol. 99, 1972–1980. https://doi.org/ 10.1016/J.BIORTECH.2007.03.056. Núñez, L.A., Martínez, B., 1999. Anaerobic treatment of slaughterhouse wastewater in an Expanded Granular Sludge Bed (EGSB) reactor. Water Sci. Technol. 40, 99–106. https://doi.org/10.1016/S0273-1223(99)00614-9. Núñez, L.A., Martínez, B., 2001. Evaluation of an anaerobic/aerobic system for carbon and nitrogen removal in slaughterhouse wastewater. Water Sci. Technol. 44, 271–277. Obaja, D., Macé, S., Costa, J., Sans, C., Mata-Alvarez, J., 2003. Nitrification, denitrification and biological phosphorus removal in piggery wastewater using a sequencing batch reactor. Bioresour. Technol. 87, 103–111. https://doi.org/10.1016/S0960-8524 (02)00229-8. Odong, R., Kansiime, F., Omara, J., Kyambadde, J., 2015. Tertiary treatment of abattoir wastewater in a horizontal subsurface flow-constructed wetland under tropical conditions. Int. J. Environ. Waste Manag. 15, 257. https://doi.org/10.1504/ IJEWM.2015.069160. O'Flynn, T., 1999. Operating experiences of a treatment plant designed for biological nutrient removal by pilot trials and mathematical modelling. Resour. Conserv. Recycl. 27, 117–124. https://doi.org/10.1016/S0921-3449(98)00091-3. Oğuz, M., Oğuz, M., 1993. Characterization of Ankara meat packing plant wastewater and treatment with a rotating biological contactor. Int. J. Environ. Stud. 44, 39–44. https:// doi.org/10.1080/00207239308710845. Oller, I., Malato, S., Sánchez-Pérez, J.A., 2011. Combination of Advanced Oxidation Processes and biological treatments for wastewater decontamination—a review. Sci. Total Environ. 409, 4141–4166. https://doi.org/10.1016/J.SCITOTENV.2010.08.061. Pabón, S.L., Suárez Gélvez, J.H., 2009. Starting-up and operating a full-scale activated sludge system for slaughterhouse wastewater. Ing. e Investig. 29, 53–58. Pagés-Díaz, J., Westman, J., Taherzadeh, M.J., Pereda-Reyes, I., Horváth, I.S., 2015. Semicontinuous co-digestion of solid cattle slaughterhouse wastes with other waste streams: interactions within the mixtures and methanogenic community structure. Chem. Eng. J. 273, 28–36. Pal, S., Banat, F., Almansoori, A., Abu Haija, M., 2016. Review of technologies for biotreatment of refinery wastewaters: progress, challenges and future opportunities. Environmental Technology Reviews https://doi.org/10.1080/ 21622515.2016.1164252. Palatsi, J., Viñas, M., Guivernau, M., Fernandez, B., Flotats, X., 2011. Anaerobic digestion of slaughterhouse waste: main process limitations and microbial community interactions. Bioresour. Technol. 102 (3), 2219–2227. Pan, M., Chen, T., Hu, Z., Zhan, X., 2013. Assessment of nitrogen and phosphorus removal in an intermittently aerated sequencing batch reactor (IASBR) and a sequencing batch reactor (SBR). Water Sci. Technol. 68 (2), 400–405. Pan, M., Henry, L.G., Liu, R., Huang, X., Zhan, X., 2014a. Nitrogen removal from slaughterhouse wastewater through partial nitrification followed by denitrification in intermittently aerated sequencing batch reactors at 11 °C. Environ. Technol. 35, 470–477. https://doi.org/10.1080/09593330.2013.832336. Pan, M., Wen, X., Wu, G., Zhang, M., Zhan, X., 2014b. Characteristics of nitrous oxide (N2O) emission from intermittently aerated sequencing batch reactors (IASBRs) treating slaughterhouse wastewater at low temperature. Biochem. Eng. J. 86, 62–68. https:// doi.org/10.1016/J.BEJ.2014.03.003. Peña, M.R., Rodriguez, J., Rodriguéz, J., Mara, D.D., Sepulveda, M., 2000. Greenhouse Gases From Wastewater Treatment View Project Study and Characterization of Constructed Wetlands Functionality by Laser Induced Fluorescence Spectroscopy View Project UASBs or Anaerobic Ponds in Warm Climates? A Preliminary Answer From Colombia. https://doi.org/10.2166/wst.2000.0609. Peng, Y., Zhu, G., 2006. Biological nitrogen removal with nitrification and denitrification via nitrite pathway. Appl. Microbiol. Biotechnol. 73 (1), 15–26. Phillips, S.A., 1975. Wastewater treatment plant handles cattle killing waste. Water & Sewage Works, pp. 50–51 August. Pijuan, M., Yuan, Z., 2010. Development and optimization of a sequencing batch reactor for nitrogen and phosphorus removal from abattoir wastewater to meet irrigation standards. Water Sci. Technol. 61, 2105–2112. https://doi.org/10.2166/wst.2010.973. Polprasert, C., Kemmadamrong, P., Tran, F.T., 1992. Anaerobic baffle reactor (ABR) process for treating a slaughterhouse wastewater. Environ. Technol. 13, 857–865. https://doi. org/10.1080/09593339209385220. Poommai, S., Pitaktunsakul, P., Chunkao, K., Dampin, N., 2015. Vertical-flow constructed wetlands in cooperating with oxidation ponds for high concentrated COD and BOD pig-slaughterhouse wastewater treatment system at Suphanburi-provincial municipality. Mod. Appl. Sci. 9. https://doi.org/10.5539/mas.v9n8p371 Vertical-Flow Constructed Wetlands in Cooperating with Oxidation Ponds for High Concentrated COD and BOD Pig-Slaughterhouse Wastewater Treatment System at SuphanburiProvincial Mun…. Rajab, A.R., Salim, M.R., Sohaili, J., Anuar, A.N., Salmiati, Lakkaboyana, S.K., 2017. Performance of integrated anaerobic/aerobic sequencing batch reactor treating poultry

707

slaughterhouse wastewater. Chem. Eng. J. 313, 967–974. https://doi.org/10.1016/J. CEJ.2016.10.144. Rajagopal, R., Massé, D.I., Singh, G., 2013. A critical review on inhibition of anaerobic digestion process by excess ammonia. Bioresour. Technol. 143, 632–641. https://doi. org/10.1016/J.BIORTECH.2013.06.030. Rajakumar, R., Meenambal, T., 2008. Comparative study on start-up performance of HUASB and AF reactors treating poultry slaughterhouse wastewater. Int. J. Environ. Res 2, 401–410. Rajakumar, R., Meenambal, T., Banu, J.R., Yeom, I.T., 2011. Treatment of poultry slaughterhouse wastewater in upflow anaerobic filter under low upflow velocity. International Journal of Environmental Science & Technology 8 (1), 149–158. Rajakumar, R., Meenambal, T., Saravanan, P.M., Ananthanarayanan, P., 2012. Treatment of poultry slaughterhouse wastewater in hybrid upflow anaerobic sludge blanket reactor packed with pleated poly vinyl chloride rings. Bioresour. Technol. 103, 116–122. https://doi.org/10.1016/J.BIORTECH.2011.10.030. Rao, P.V., Baral, S.S., Dey, R., Mutnuri, S., 2010. Biogas generation potential by anaerobic digestion for sustainable energy development in India. Renew. Sust. Energ. Rev. 14, 2086–2094. https://doi.org/10.1016/J.RSER.2010.03.031. Rinzema, A., Alphenaar, A., Lettinga, G., 1993. Anaerobic digestion of long-chain fatty acids in UASB and expanded granular sludge bed reactors. Process Biochem. 28, 527–537. https://doi.org/10.1016/0032-9592(93)85014-7. Rodríguez-Méndez, R., Le Bihan, Y., Béline, F., Lessard, P., 2017. Long chain fatty acids (LCFA) evolution for inhibition forecasting during anaerobic treatment of lipid-rich wastes: case of milk-fed veal slaughterhouse waste. Waste Manag. 67, 51–58. https://doi.org/10.1016/J.WASMAN.2017.05.028. Rosa, D.R., Cammarota, M.C., Freire, D.M.G., 2006. Production and utilization of a novel solid enzymatic preparation produced by Penicillium restrictum in activated sludge systems treating wastewater with high levels of oil and grease. Environ. Eng. Sci. 23, 814–823. https://doi.org/10.1089/ees.2006.23.814. Ruiz, I., Veiga, M.C., de Santiago, P., Blázquez, R., 1997. Treatment of slaughterhouse wastewater in a UASB reactor and an anaerobic filter. Bioresour. Technol. 60, 251–258. https://doi.org/10.1016/S0960-8524(97)00020-5. Ruiz, C., Torrijos, M., Sousbie, P., Lebrato Martinez, J., Moletta, R., 2001. The anaerobic SBR process: basic principles for design and automation. Water Sci. Technol. 43, 201–208. https://doi.org/10.2166/wst.2001.0138. Russell, J.M., van Oostrom, A.J., Lindsey, S.B., 1994. Denitrifying sites in constructed wetlands treating agricultural industry wastes: a note. Environ. Technol. 15, 95–99. https://doi.org/10.1080/09593339409385408. Saddoud, A., Sayadi, S., 2007. Application of acidogenic fixed-bed reactor prior to anaerobic membrane bioreactor for sustainable slaughterhouse wastewater treatment. J. Hazard. Mater. 149, 700–706. https://doi.org/10.1016/J. JHAZMAT.2007.04.031. Safley, L.M., Westerman, P.W., 1988. Biogas production from anaerobic lagoons. Biol. Wastes 23, 181–193. https://doi.org/10.1016/0269-7483(88)90033-X. Safley, L.M., Westerman, P.W., 1992. Performance of a low temperature lagoon digester. Bioresour. Technol. 41, 167–175. https://doi.org/10.1016/0960-8524(92)90188-4. Saghir, A., Hajjar, S., 2018. The Treatment of Slaughterhouses Wastewater by an Up Flow - Anaerobic Sludge Blanket (Uasb) Reactor. https://doi.org/10.16984/ saufenbilder.328852. Salminen, E.A., Rintala, J.A., 1999. Anaerobic digestion of poultry slaughtering wastes. Environ. Technol. 20, 21–28. https://doi.org/10.1080/09593332008616788. Salminen, E., Rintala, J., 2002. Anaerobic digestion of organic solid poultry slaughterhouse waste–a review. Bioresour. Technol. 83 (1), 13–26. Salminen, E., Einola, J., Rintala, J., 2001. Characterisation and anaerobic batch degradation of materials accumulating in anaerobic digesters treating poultry slaughterhouse waste. Environ. Technol. 22, 577–585. https://doi.org/10.1080/09593332208618261. Sawyer, C.N., McCarty, P.L., Parkin, G.F., 2003. Chemistry for Environmental Engineering and Science. fifth ed. McGraw Hill. Sayed, S.K.I., 1987. Anaerobic Treatment of Slaughterhouse Wastewater Using the UASB Process. Schneider, E., Cerqueira, A.C.F.P., Dezotti, M., 2011. MBBR evaluation for oil refinery wastewater treatment, with post-ozonation and BAC, for wastewater reuse. Water Sci. Technol. 63 (1), 143–148. Scholz, M., 2006. Comparison of novel membrane bioreactors and constructed wetlands for treatment of pre-processed animal rendering plant wastewater in Scotland. EWater ((on-line Publ. EWA), 14 pp.). Sengar, A., Aziz, A., Farooqi, I.H., Basheer, F., 2018a. Development of denitrifying phosphate accumulating and anammox micro-organisms in anaerobic hybrid reactor for removal of nutrients from low strength domestic sewage. Bioresour. Technol. 267, 149–157. https://doi.org/10.1016/J.BIORTECH.2018.07.023. Sengar, A., Basheer, F., Aziz, A., Farooqi, I.H., 2018b. Aerobic granulation technology: laboratory studies to full scale practices. J. Clean. Prod. 197. https://doi.org/10.1016/j. jclepro.2018.06.167. Seyhi, B., Drogui, P., Buelna, G., Blais, J.F., 2011. Modeling of sorption of bisphenol A in sludge obtained from a membrane bioreactor process. Chem. Eng. J. 172, 61–67. https://doi.org/10.1016/J.CEJ.2011.05.065. Shengquan, Y., Siyuan, G., Hui, W., 2008. High effective to remove nitrogen process in abattoir wastewater treatment. Desalination 222, 146–150. https://doi.org/10.1016/J. DESAL.2007.01.140. Shi, X., Lefebvre, O., Ng, K.K., Ng, H.Y., 2014. Sequential anaerobic–aerobic treatment of pharmaceutical wastewater with high salinity. Bioresour. Technol. 153, 79–86. https://doi.org/10.1016/J.BIORTECH.2013.11.045. Silva, S.A., Cavaleiro, A.J., Pereira, M.A., Stams, A.J.M., Alves, M.M., Sousa, D.Z., 2014. Long-term acclimation of anaerobic sludges for high-rate methanogenesis from LCFA. Biomass Bioenergy 67, 297–303. https://doi.org/10.1016/J. BIOMBIOE.2014.05.012.

708

A. Aziz et al. / Science of the Total Environment 686 (2019) 681–708

Sirianuntapiboon, S., 2006. Treatment of wastewater containing Cl2 residue by packed cage rotating biological contactor (RBC) system. Bioresour. Technol. 97, 1735–1744. https://doi.org/10.1016/J.BIORTECH.2005.07.030. Sirianuntapiboon, S., Yommee, S., 2006. Application of a new type of moving bio-film in aerobic sequencing batch reactor (aerobic-SBR). J. Environ. Manag. 78, 149–156. https://doi.org/10.1016/J.JENVMAN.2005.04.012. Skjelhaugen, O.J., Donantoni, L., 1998. Combined aerobic and electrolytic treatment of cattle slurry. J. Agric. Eng. Res. 70, 209–219. https://doi.org/10.1006/ JAER.1998.0267. Soroko, M., 2007. Treatment of wastewater from small slaughterhouse in hybrid constructed wetlands systems. Ecohydrol. Hydrobiol. 7, 339–343. https://doi.org/ 10.1016/S1642-3593(07)70117-9. Sousa, D.Z., Smidt, H., Alves, M.M., Stams, A.J.M., 2009. Ecophysiology of syntrophic communities that degrade saturated and unsaturated long-chain fatty acids. FEMS Microbiol. Ecol. 68, 257–272. https://doi.org/10.1111/j.1574-6941.2009.00680.x. Sriwiriyarat, T., Ungkurarate, W., Fongsatitkul, P., Chinwetkitvanich, S., 2008. Effects of dissolved oxygen on biological nitrogen removal in integrated fixed film activated sludge (IFAS) wastewater treatment process. J. Environ. Sci. Heal. Part A 43, 518–527. Sroka, E., Kamiński, W., Bohdziewicz, J., 2004. Biological treatment of meat industry wastewater. Desalination 162, 85–91. https://doi.org/10.1016/S0011-9164(04) 00030-X. Stebor, T.W., Berndt, C.L., Marman, S., Gabriel, R., 1990. Operating experience: anaerobic treatment at packerland packing. Proceedings of the Industrial Waste Conference. Purdue University. Steele, M.T., Hamilton, D.W., 2010. Continuous operation of a full scale anaerobic sequencing batch reactor treating low strength swine manure. 2010 Pittsburgh, Pennsylvania, June 20–June 23, 2010. American Society of Agricultural and Biological Engineers, p. 1. Steiner, A., 1987. Stand der Technik bei der anaeroben handlung von Schlachthofabwässemrn. Münchener Beitrage zur Abwasser-, Fischerei-und Fluβbiologie, pp. 41–266. Stephenson, T., Lester, J.N., 1986. Evaluation of startup and operation of four anaerobic processes treating a synthetic meat waste. Biotechnol. Bioeng. 28, 372–380. https:// doi.org/10.1002/bit.260280310. Stets, M.I., Etto, R.M., Galvão, C.W., Ayub, R.A., Cruz, L.M., Steffens, M.B.R., Barana, A.C., 2014. Microbial community and performance of slaughterhouse wastewater treatment filters. Genet. Mol. Res. 13, 4444–4455. Struseviciene, S.M., Strusevicius, Z., 2006. Efficiency of Wastewater Treatment in Slaughterhouse in Two-stage Constructed Wetlands. Subramaniam, K., Greenfield, P.F., Ho, K.M., Johns, M.R., Keller, J., 1994. Efficient biological nutrient removal in high strength wastewater using combined anaerobic-sequencing batch reactor treatment. Water Sci. Technol. 30, 315. Sung, S., Dague, R.R., 1995. Laboratory studies on the anaerobic sequencing batch reactor. Water Environ. Res. 67, 294–301. https://doi.org/10.2175/ 106143095X131501. Tanji, K., Ong, C., Dahlgren, R., Herbel, M., 1992. Salt deposits in evaporation ponds: an environmental hazard? Calif. Agric. 46, 18–21. Tanwar, P., Nandy, T., Khan, R., Biswas, R., 2007. Intermittent cyclic process for enhanced biological nutrient removal treating combined chemical laboratory wastewater. Bioresour. Technol. 98 (13), 2473–2478. Taşkan, E., 2016. Performance of mixed algae for treatment of slaughterhouse wastewater and microbial community analysis. Environ. Sci. Pollut. Res. 23 (20), 20474–20482. Tchobanoglous, G., Burton, F.L., Stensel, H.D., 2003. Wastewater Engineering Treatment and Reuse. McGraw-Hill Higher Education, Boston, US. Tezel, U., Guven, E., Erguder, T.H., Demirer, G.N., 2001. Sequential (anaerobic/aerobic) biological treatment of Dalaman SEKA Pulp and Paper Industry effluent. Waste Manag. 21, 717–724. https://doi.org/10.1016/S0956-053X(01)00013-7. Thayalakumaran, N., Bhamidimarri, R., Bickers, P.O., 2003. Biological nutrient removal from meat processing wastewater using a sequencing batch reactor. Water Sci. Technol. 47, 101–108. https://doi.org/10.2166/wst.2003.0549. Toldrá, F., Flors, A., Lequerica, J.L., Vallés, S., 1987. Fluidized bed anaerobic biodegradation of food industry wastewaters. Biol. Wastes 21, 55–61. https://doi.org/10.1016/02697483(87)90146-7. Torkian, A., Alinejad, K., Hashemian, S.J., 2003a. Posttreatment of upflow anaerobic sludge blanket-treated industrial wastewater by a rotating biological contactor. Water Environ. Res. 75, 232–237. https://doi.org/10.2175/106143003X141015. Torkian, A., Eqbali, A., Hashemian, S., 2003b. The effect of organic loading rate on the performance of UASB reactor treating slaughterhouse effluent. Resour. Conserv. Recycl. 40, 1–11. https://doi.org/10.1016/S0921-3449(03)00021-1. Toze, S., 1999. PCR and the detection of microbial pathogens in water and wastewater. Water Res. 33, 3545–3556. https://doi.org/10.1016/S0043-1354(99)00071-8.

Travers, Sm, Lovett, D.A., 1984. Activated sludge treatment of abattoir wastewater—II: Influence of dissolved oxygen concentration. Water Res. 18, 435–439. Tritt, W.P., 1992. The anaerobic treatment of slaughterhouse wastewater in fixed-bed reactors. Bioresour. Technol. 41, 201–207. https://doi.org/10.1016/0960-8524(92) 90002-F. Van Oostrom, A.J., 1995. Nitrogen removal in constructed wetlands treating nitrified meat processing effluent. Water Sci. Technol. 32, 137–147. https://doi.org/10.1016/02731223(95)00614-1. Viraraghavan, T., Varadarajan, R., 1996. Low-temperature kinetics of anaerobic-filter wastewater treatment. Bioresour. Technol. 57, 165–171. https://doi.org/10.1016/ 0960-8524(96)00067-3. Von Sperling, M., Freire, V.H., De Lemos Chernicharo, C.A., 2001. Performance evaluation of a UASB-activated sludge system treating municipal wastewater. Water Sci. Technol. 43, 323–328. Vymazal, J., 2011. Constructed wetlands for wastewater treatment: five decades of experience †. Environ. Sci. Technol. 45, 61–69. https://doi.org/10.1021/es101403q. Vymazal, J., 2014. Constructed wetlands for treatment of industrial wastewaters: a review. Ecol. Eng. 73, 724–751. https://doi.org/10.1016/J.ECOLENG.2014.09.034. Wang, Q., Kuninobu, M., Ogawa, H.I., Kato, Y., 1999. Degradation of volatile fatty acids in highly efficient anaerobic digestion. Biomass Bioenergy 16 (6), 407–416. Wang, S., Hawkins, G.L., Kiepper, B.H., Das, K.C., 2018. Treatment of slaughterhouse blood waste using pilot scale two-stage anaerobic digesters for biogas production. Renew. Energy 126, 552–562. https://doi.org/10.1016/J.RENENE.2018.03.076. Willers, H.C., ten Have, P.J.W., Derikx, P.J.L., Arts, M.W., 1993. Temperature-dependency of nitrification and required anoxic volume for denitrification in the biological treatment of veal calf manure. Bioresour. Technol. 43, 47–52. https://doi.org/10.1016/ 0960-8524(93)90081-L. Winkler, M.K., Straka, L., 2019. New directions in biological nitrogen removal and recovery from wastewater. Curr. Opin. Biotechnol. 57, 50–55. Wirtz, R.A., Dague, R.R., 1996. Enhancement of granulation and start-up in the anaerobic sequencing batch reactor. Water Environ. Res. 68, 883–892. https://doi.org/10.2175/ 106143096X127893. Wong, B.-T., Show, K.-Y., Su, A., Wong, R., Lee, D.-J., 2007. Effect of volatile fatty acid composition on upflow anaerobic sludge blanket (UASB) performance. Energy Fuel 22, 108–112. World Bank Group, 2007. Environmental, Health and Safety Guidelines for Meat Processing. https://www.ifc.org/wps/wcm/connect/e9ae040048865967b912fb6a6515bb18/ Final%2B-%2BMeat%2BProcessing.pdf?MOD=AJPERES, Accessed date: 19 September 2018. Yacob, S., Ali Hassan, M., Shirai, Y., Wakisaka, M., Subash, S., 2006. Baseline study of methane emission from anaerobic ponds of palm oil mill effluent treatment. Sci. Total Environ. 366, 187–196. https://doi.org/10.1016/J.SCITOTENV.2005.07.003. Yadvika, Santosh, Sreekrishnan, T.R., Kohli, S., Rana, V., 2004. Enhancement of biogas production from solid substrates using different techniques––a review. Bioresour. Technol. 95, 1–10. https://doi.org/10.1016/J.BIORTECH.2004.02.010. Yan, L., Ye, J., Zhang, P., Xu, D., Wu, Y., Liu, J., Zhang, H., Fang, W., Wang, B., Zeng, G., 2018. Hydrogen sulfide formation control and microbial competition in batch anaerobic digestion of slaughterhouse wastewater sludge: effect of initial sludge pH. Bioresour. Technol. 259, 67–74. Young, J.C., Mccarty, P.L., 1969. The anaerobic filter for waste treatment. J. (Water Pollut. Control FEd.) 41, 160–173. Zeng, R.J., Lemaire, R., Yuan, Z., Keller, J., 2004. A novel wastewater treatment process: simultaneous nitrification, denitrification and phosphorus removal. Water Sci. Technol. 50 (10), 163–170. Zhan, X., Healy, M.G., Li, J., 2009. Nitrogen removal from slaughterhouse wastewater in a sequencing batch reactor under controlled low DO conditions. Bioprocess Biosyst. Eng. 32, 607–614. https://doi.org/10.1007/s00449-008-0283-8. Zhang, Q., Hu, J., Lee, D.J., 2016. Aerobic granular processes: current research trends. Bioresour. Technol. 210, 74–80. https://doi.org/10.1016/j.biortech.2016.01.098. Zhao, X., Ma, J., Ma, H., Gao, D., Sun, Y., Guo, C., 2018. Removal of polyacrylate in aqueous solution by activated sludge: characteristics and mechanisms. J. Clean. Prod. 178, 59–66. https://doi.org/10.1016/J.JCLEPRO.2017.12.215. Zheng, Z., Liu, J., Yuan, X., Wang, X., Zhu, W., Yang, F., Cui, Z., 2015. Effect of dairy manure to switchgrass co-digestion ratio on methane production and the bacterial community in batch anaerobic digestion. Appl. Energy 151, 249–257. Zinatizadeh, A.A.L., Ghaytooli, E., 2015. Simultaneous nitrogen and carbon removal from wastewater at different operating conditions in a moving bed biofilm reactor (MBBR): process modeling and optimization. J. Taiwan Inst. Chem. Eng. 53, 98–111. https://doi.org/10.1016/J.JTICE.2015.02.034.