Performance improvement of an integrated anaerobic-aerobic hybrid reactor for the treatment of swine wastewater

Journal of Water Process Engineering 34 (2020) 101164

Contents lists available at ScienceDirect

Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe

Performance improvement of an integrated anaerobic-aerobic hybrid reactor for the treatment of swine wastewater

T

Perla A. Gonzalez-Tineoa, Ulises Durán-Hinojosac, Liliana R. Delgadillo-Mirquezd, Edna R. Meza-Escalantea, Pablo Gortáres-Moroyoquib, Ruth G. Ulloa-Mercadob, Denisse Serrano-Palaciosa,* a

Departamento De Ciencias Del Agua y Medio Ambiente. Instituto Tecnológico De Sonora. Calle 5 De Febrero 818 Sur. Col. Centro. Cd. Obregón, Sonora, Mexico Departamento De Biotecnología y Ciencias Alimentarias. Instituto Tecnológico De Sonora. Calle 5 De Febrero 818 Sur. Col. Centro. Cd. Obregón, Sonora, Mexico c Instituto De Ingeniería, UNAM, P.O. Box 70-186, Mexico City, Mexico d Facultad De Ingeniería. Universidad De Ibagué. Carrera 22 Calle 67 B/Ambalá: Ibagué, Tolima, Colombia b

A R T I C LE I N FO

A B S T R A C T

Keywords: Organic load rate Ammonification Hybrid reactor Specific methanogenic activity Swine wastewater

In this study, performance of a lab-scale anaerobic-aerobic hybrid reactor, treating swine wastewater was evaluated under three different organic loading rates (OLR). The operating of integral hybrid system consisted of two experimental sections: first, an UASB section, and second, a UASB section + aerobic packed-bed with polyethylene rings. During the reactor operation, three assays of SMA were carried out and according to these results (0.26, 0.32 and 0.81 kg COD-CH4/kg VSS·d), the OLR was gradually step increased from 3.26 to 4.02 and finally 10.14 kg COD/m3·d. With this strategy, the removal efficiency of organic matter during the last operational condition increased 34.3% compared to the initial, using the SMA as a control tool. In addition, the nitrogen accumulated that could not be removed in the UASB section was treated by the aerobic packed bed, by nitrification-denitrification simultaneous achieving almost a total removal. This removal was attributed 55 ± 11% to nitrification process, 30% to denitrification and stripping were 11 ± 1%. Therefore, this anaerobicaerobic hybrid reactor is an integral unit that allowed greater operating efficiencies than other hybrid systems that operate in two or more units, and is capable of complying with current regulations for discharge to water bodies.

1. Introduction It is estimated that in Mexico a pig produces around 0.27 m3 of effluent every month (feces and urine) [1], and it is report that around 38% of pig farms disposed their wastes without any treatment directly into soils and water bodies [2]. In addition, other authors reported that almost no farm in Mexico complies with Mexican regulations for discharge into water and national goods [3]. The above mentioned generates a significant impact on the environment owing to the large volumes of solids and wastewater generated in the pig farm whish altering the physical, chemical and microbiology composition of solid and water bodies [4]. Another important pollutant that has been found in the effluent of pig farms is total nitrogen and can be present in a concentration range between 524 to 1907 mg/L [3]. In this regard, systems used to treat porcine effluents are those focused on the removal of organic matter like: biodigesters with efficiencies ≤50% [5], anaerobic ponds ≤56% [6], facultative ponds ≤30% [3] and UASB reactors ⁎

≤60% [6]. On the contrary, organic nitrogenous compounds present in the wastewater, like proteins, amino-acids or urea, are mainly reduced to ammonia which is poorly degraded on anaerobic conditions [7]. Limited performance of nitrogen removal has been reported in anaerobic system; some examples are those reported by Karakashev et al. [6] in a UASB reactor with removal efficiencies of ≤ 11% and in an anaerobic digester of 0%. Techio et al. [5] reported removal of ≤ 56% using anaerobic ponds and biodigesters efficiencies were -17%. Quite often, the low nitrogen removal leads an unsuccessful anaerobic process accompanied with an acidification, and negative effects in the biogas production rate. Therefore, these biological processes are ungood enough to produce acceptable quality effluents to reuse in agricultural irrigation or included in the pig farm according to the legal Mexican standard. Due to the need to improve not only the removal of organic matter but also nutrients such as nitrogen, new wastewater treatment systems called hybrids have been introduced in the last years, which combine

Corresponding author. E-mail address: [email protected] (D. Serrano-Palacios).

https://doi.org/10.1016/j.jwpe.2020.101164 Received 12 October 2019; Received in revised form 10 January 2020; Accepted 23 January 2020 2214-7144/ © 2020 Elsevier Ltd. All rights reserved.

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

biological, chemical and/or physical processes in a single system or separated units [8,9]. Anaerobic hybrid reactors have been used to treat successfully industrial effluents, recalcitrant compounds and high loads of organic matter, such as, for example effluents from distilleries [10], slaughterhouses or pig farms [11]. Hybrid reactors are efficient, costeffective and small space requirement [12]. In addition, the used of support media into the hybrid reactors could improves the developed of biofilm biomass to increase pollutant removal and system stability due to the high sludge retention time (SRT) leads to the formation of bacterial community such as nitrifies and denitrifies microorganisms [13]. As a result, higher organic matter removal rates and better effluent quality are achieved in these systems compared to conventional processes treatment [14]. Despite these advantages, there are poor reported hybrid technologies to swine wastewater treatment [15,11]. In this context, it is necessary a new type of integral systems more efficient at higher organic matter and nitrogen removal, that operate with short HRT (< 1 d) and high OLR (> 10 kg COD/m3∙d) that allow to treat the significant amounts of swine wastes produced daily. The success of hybrid systems depends on the substrate and the quality of the biomass. Swine wastewater represent a good substrate that promotes the growth of anaerobic microorganisms, thanks to its content of carbohydrates (53%), hemicellulose and cellulose (20%) followed by proteins (20%), fats and lipids (7%) and a small amount of lignin (4.4%) and starch (1.6%) [16]. In addition, the high performance of a hybrid reactor which is contained an anaerobic section depends on the presence of an adequate level of methanogenic activity. Therefore, it is necessary to monitor changes in the groups or activities of the methanogenic microorganisms in the digester using such available techniques as a microscope count, most probable number, coenzyme F420 quantification or the Specific Methanogenic Activity (SMA) [17]. The disadvantage of some of these techniques is that is not practical and is too complex to the routine analysis. Nevertheless, the SMA technique is more rapid and reliable than the other test [18]. SMA is defined as the methane production capacity of a specific methanogenic population for a precise substrate, where the availability of the substrate is not a limiting factor [19]. Moreover, the SMA is also a valuable tool to determine the maximum Organic Load Rate (OLR) to be treated in a system, maintaining the capacity of anaerobic microorganisms to remove biodegradable organic matter and produce methane [20]. According to Yan and Tay [21] the OLR must correspond to the 60–80% of the SMA value, which has been proved as appropriate for rapid start-up to anaerobic system. This ratio resulting in high operating stability and an excellent COD removal in the anaerobic system, however, a low COD removal and poor stability can result when 80% of the value of the SMA is exceeded. The SMA test can be complemented with the quantification of Volatile Suspended Solids (VSS) to differentiate between active microbial biomass and any other inert particulate material [22]. The SMA has been used by several authors in various anaerobic processes. McHugh et al. [23] investigated the microbial community structure with the application the SMA test during the startup of psychrophilic anaerobic digesters treating Volatile Fatty Acids (VFA) and sucrose, which reached a high COD removal efficiency (90%) at an OLR of 20 kg COD/m3·d, as a consequence of a shift of the dominance response from acetoclastic to hydrogenotrophic. Oktem et al. [24] used a SMA initial test to control the OLR in the range of 3 to 9 kg COD/m3·d in a hybrid UASB reactor treating pharmaceutical wastewater, evidencing there was no obvious inhibitory effect and a 99% of COD removal was achieved. On the contrary, Wijekoon et al. [25] operated a Thermophilic Anaerobic Membrane Bioreactor (TAnMBR) to molasses residues treatment. The SMA test was used before OLR changes, though the COD removal decreased from 81 to 61% when the OLR increasing from 8 to 12 kg COD/m3·d. Based on these reports, it is important to emphasize the suitability of the anaerobicaerobic hybrid system in a unique unit for treatment of swine wastewater has been uninvestigated with the contribution of pertinent SMA information.

Table 1 Characteristics of the swine wastewater from a swine maternity farm. Parameters*

Concentration (g/L)

Total chemical oxygen demand (CODt) Soluble chemical oxygen demand (CODs) Nitrates as nitrogen (NO3--N) Nitrites as nitrogen (NO2--N) Ammonium as nitrogen (NH4+-N) Total solids (TS) Total volatile solids (TVS) Total carbohydrates Total proteins

11-55 5-12.5 0-0.13 0-0.2 0.4-2.1 12-42.5 11.8–32.5 0-0.3 0-0.7

*The parameters were quantified according to the techniques described in the analytical methods section.

In this context, the aim of this study was to develop an anaerobicaerobic hybrid reactor for the removal of macropollutants from swine wastewater. On one hand, the removal of the intensest amount of organic matter was carried out through the anaerobic section using the SMA as a control tool, for the purpose of to improve the operational efficiencies in a hybrid system. On the other hand, the aerobic packed bed section treated the nitrogen accumulated that could be unremoved by the anaerobic sludge by nitrification-denitrification simultaneous. 2. Materials and methods 2.1. Swine wastewater characteristics Swine wastewater was obtained from a pig farm located in Sonora Mexico. The parameters evaluated are shown in Table 1, and correspond to the effluents generated in a maternity farm. The ranges presented correspond to nine sample lots of wastewater analyzed during the 500 days of the operation of the hybrid reactor. The swine wastewater fed to the hybrid reactor was previously conditioned. In order to reduce the size of large solids and to prevent clogging system pipes, the liquid waste efficiently was blende and strain. Subsequently, the wastewater was diluted to achieve by adequate concentration of COD in the influent that fed to the system. 2.2. Characteristics of the anaerobic and aerobic biomass The anaerobic biomass was obtained from a stable UASB reactor used to treat wastewater from a brewery (Cervecería Cuauhtémoc Moctezuma) in Mexico City. The inoculum presented suitable physical characteristics such as an initial concentration of TSS of 33.93 g/L and VSS of 31.71 g/L and it was constituted by 96% of granules with an approximate diameter of 0.6 cm, with a sedimentation rate of 42.56 m/ h and a Sludge Volume Index (SVI) of 37 mL/g TSS. In addition, the inoculum was previously adapted with brewery wastewater at high OLR. Nitrifying biomass was obtained from an urban wastewater treatment plant located south of Ciudad Obregón, México. The aerobic biomass had a concentration of 20.4 g/L of TSS and 7.66 g/L of VSS. The initial physical characteristics of the biomass was a flocculent form with poor sedimentation (SVI > 200 mL/g TSS). 2.3. Start-up and operation of the anaerobic-aerobic hybrid reactor The experiment was carried out in a laboratory-scale hybrid reactor with a useful volume between 2 and 3 L, a flow rate of 2.82 ± 0.76 L/d and Hydraulic Retention Time (HRT) of 0.79 ± 0.20 days. A schematic representation of hybrid reactor is shown in Fig. 1. The system was configured in two-sections: (a) start-up and stabilization of the UASB section under anaerobic conditions (0–188 days) with an initial volume of 2 L, and (b) UASB section + aerobic packed bed (189–500 days) with 2

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

Fig. 1. Schematic diagram of the anaerobic-aerobic hybrid reactor.

a total volume of 3 L. The UASB section was inoculated with 800 mL of anaerobic granular sludge, which corresponded to a third of the volume’s section. The temperature inside the reactor was adjusted by an external, thermostatically controlled, hot water serpentine. On the other hand, the aerobic packed bed section was installed, which had a volume of 0.9 L, with a flow air that supply an average oxygen concentration of 3.35 mg/L provide by a flow meter. This section was filled with polyethylene rings of 3 cm in diameter and 3 cm in height, and a density of 77.8 g/L. The rings, used as support media, promoted the colonization of a biofilm inside and outside of them. The operation of the hybrid reactor was divided in three periods in which the OLR was increased progressively. The SMA measure was used previously to stablish each change in the OLR, as control tool for the reactor operation. The OLR was gradually increased from 3.26 (0–174 days) up to 4.02 (175–459 days), and finally to 10.17 kg COD/m3·d (460–500 days), according to the SMA test results. Therefore, the system constantly operated below its maximum OLR established by the SMA test avoiding exceeding the capacity of the anaerobic microorganisms due to the supplied substrate. Finally, the OLR increments were made by increasing the COD concentration in the feeding trying to have a constant flow.

(3.000). The operating conditions of the anaerobic tests were a substrate/biomass ratio of 0.4 g COD/g VSS, a temperature of 37 ± 2 °C and a pH of 7. Quantification of produced CH4 was carried out by gas chromatography (Fisher Gas Partitioner model 1200 with a thermal conductivity detector and a Porapak Q column). The SMA value (Eq. 1) was estimated by plotting the production of CH4 (kg of COD) against time (days) and dividing by the amount of VSS added to each bottle.

SMA(kg COD-CH 4 /KgVSS∙d)=

Methane production (kg COD-CH4/d) Biomass (kg VSS) (1)

Once the SMA was determined, the maximum OLR allowed by the reactor (kg COD−CH4/m3·d) was calculated with Eq. 2:

V OLR(kg COD/m3∙d) = ⎛ l ⎞ (VSS) (SMA) ⎝ Vr ⎠ ⎜

⎟

(2) 3

Where Vl is the volume of biomass in the reactor (m ), Vr is the reactor volume (m3), VSS is the amount of volatile suspended solids (kg/m3) and the SMA value of the biomass (kg COD−CH4/kg VSS·d). 2.5. Analytical methods

2.4. Determination of specific methanogenic activity (SMA)

The anaerobic biomass was used to calculate the sedimentation velocity, the Sludge Volume Index (SVI) and the distribution size of the granules, which was measured through 6- and 4-mm sieves. In the influent and effluent of the hybrid reactor, the following analyzes were performed: COD, Total solids (TS), Total Volatile Solids (TVS), NO3− -N -, NO2- -N, NH4+-N according to the [26]. Other parameters such as VFAs and alkalinity were also monitored following the method described by Anderson and Yang [27] and proteins and carbohydrates

Anaerobic biomass was sampled in the days 0, 175 and 460, during the reactor operation, in order to quantify their specific activities. SMA assays were performed in 60 mL serological bottles with a working volume of 20 mL: 4 mL of the anaerobic consortium and 16 mL of a mineral medium (g/L): NaH2PO4·H2O (0.703), K2HPO4 (0.600), NH4Cl (0.500), MgSO4·7H2O (0.111), CaCl2·2H2O (0.100) and NaHCO3 3

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

Table 2 Summary of operational data for different anaerobic processes. Feed type

Sludge type

Reactor type

OLR (kg COD/ m3·d)

T (°C)

SMA (kg COD-CH4/ kg VSS·d)

HRT (days)

Reference

Brewery Whey Acetate, ethanol, butyrate Nonfat dry milk, acetate, starch Swine manure Swine manure Swine manure Poultry wastewater Cattle manure Swine manure Swine wastewater Swine manure Swine wastewater

Suspended Granule Granule Suspended Granular Granular Granular granular NR NR NR NR Granule

AnMBR EGSB + AF UASB + AF AnMBR CSTR UASB AD UASB UASB ASBR DAF AD Hybrid reactor

1.5 1.3 20 1 2 16.4 1-3 2.9 2.3 1.1 15 4 10.2

37 37 37 25 35 36 39 34 37 20 35 37 35

0.1 0.6 0.4 0.2 0.6 0.6 0.7 0.3 0.4 0.3 0.4 0.3 0.8

NR 0.5-2 0.5 0.5 30 1.5 29 0.5 22 15 5 23 0.8

[40] [41] [23] [42] [43] [38] [44] [45] [46] [47] [39] [48] This study

AnMBR: Anaerobic Membrane Bioreactor; AF: Anaerobic Filter; ASBR: Anaerobic Sequencing Batch Reactor; UASB: Up-flow Anaerobic Sludge Bed reactor; AUBF: Anaerobic Upflow Bed Filter; CSTR: Continuously Stirred Tank Reactor; AD: Anaerobic Digester; DAF: Dispersed Anaerobic Fermenter; NR: not reported.

proportional way and in a steady state stage, in which only SMA increases due to the adaptation to the substrate. Najafpour et al. [31] reported an increased in the VSS from 41.7–74.2 g/L in an upflow anaerobic sludge-fixed film bioreactor, which is reflected in an increase in SMA from 0.14 to 0.46 kg COD-CH4 /kg VSS·d at the beginning of the reactor operation. Moreover, in a steady state an increase in SMA of 0.80 kg COD-CH4 /kg VSS·d was observed when the VSS had a concentration of 75.2 g/L. Additionally, Hussain and Dubey [20] observed in a UASB, an increase in the first stage of operation of SMA and VSS from 0.25 to 0.31 COD-CH4 /kg VSS·d and from 38 to 43 g/L, respectively. However, when the VSS concentration was maintained constant in a second period of UASB operation, the SMA increased to 0.66 CODCH4 /kg VSS·d. Furthermore, the SMA value obtained in this study is similar to other reports for methanogenic activity tests based on an acetoclastic pathway in granular sludge, which must be greater than or equal to 0.45 kg COD-CH4/kg VSS·d [32]. We want to underscore that our tests, after 460 days of operation, had a value of 0.81 kg COD-CH4/kg VSS·d, indicating an adaptation to the substrate as stated above. Additionally, the SMA values obtained from the reactor were higher than that reported by Colleran et al [17]. who places a reference value of 0.1 kg COD-CH4/kg VSS·d, as a criterion of low activity in continuous anaerobic reactors. Comparing our results with other hybrid or conventional systems, Table 2 shows SMA values lowest than the obtained in this study. Furthermore, the same Table shows that systems operating with suspended biomass form had lower values of SMA (0.1 -0.2 kg COD-CH4/ kg VSS·d) than granular sludge (0.4-0.8 kg COD-CH4/kg VSS·d). The above could be supported by the fact that the suspended biomass has higher specific surface area and suffers greater inhibition, in presence of toxic compounds [33]. This can indicate the value of SMA depends, among other factors, on physical properties like the granule size. The granule size can be a direct parameter to demonstrate the growth and aging process in these microbial consortiums, and plays a significant role in the limitation of mass transport and diffusion [34]. Bhunia and Ghangrekar [35] observed that increasing the diameter of the granule in a UASB reactor, the value of SMA also increased, when using granules of 0.27 mm of diameter. The maximum value of the SMA was 0.5 kg COD-CH4/kg VSS·d, when the diameter of granules augmented to 3 mm on average. These authors mention that the resistance to substrate diffusion inside the granule increases proportionally with physical size and eventually resulting in substrate deficiency or depletion inside large-sized granules [35]. However, the particle size of the granules of the hybrid reactor was 6 mm, while the sedimentation rate was 42.56 m/h, and both parameters remained was constant in every operation period. In this case, the large particle size did not imply a problem as

using the methodology of Lowry [28] and Michael [29] respectively. 2.6. Statistical analysis of results The results are expressed as means ± standard deviation. The data were analyzed using two-way analysis of variance (ANOVA), with Minitab software (version 17.0). When the ANOVA identified differences among groups, multiple comparisons among the means were performed using HSD (honestly-significant-difference) Tukey. A significance level of P < 0.05 was chosen. 3. Results and discussion 3.1. Determination of specific methanogenic activity (SMA) In this study, three SMA values were obtained for the anaerobic biomass in three different operational times of the hybrid reactor. On day 0, the SMA was 0.26 kg COD-CH4/kg VSS·d, increased to 0.32 on day 175 and finally to 0.81 on day 460. The statistical analysis shows that the mentioned increases in the SMA of the hybrid system improved and were significantly different for each of the periods, even without detecting a notable increase in the VSS from operational periods two to three. During the first operation period (0–174 days), the increase in VSS (31.71–55.44 g/L) is attributed to the stage of exponential growth of the microorganisms, at the start-up of the process and as consequence of the adaptation of the biomass is possible to promote the growth of the methanogenic microorganisms and increase the SMA [30]. However, in the third operational period (460–500 days) there was no significant increase in the biomass concentration (57.04 g/L) with respect to the second period, so it is inferred that the increase in SMA is because the same microorganisms were capable to adapt to the swine wastewater. A distinct behavior was found by Yan and Tay [21], who report a SMA increase from 0.07 to 1.4 kg COD-CH4/kg, almost immediately after UASB reactor start-up, due to the easy biodegradability of the substrate (glucose and peptone). Since it would be wiser to start with a more biodegradable substrate than swine wastewater and which leads to the rapid bacterial adaptation. Generally, the increase in SMA is due to an increase in the biomass concentration or its adaptation to specific types of wastewaters [31]. Moreover, other reasons for the SMA increase is high substrate sufficiency applied, the appropriate environment maintained, and rapid multiplication of the methanogenic microorganisms. The behavior observed has been confirmed both Najafpour et al. [31] and Hussain and Dubay [19] whom operated working anaerobic reactors with high load rates and palm oil mill effluent and phenolic wastewaters, respectively. These researches reported both increases in SMA and VSS at the start-up period in a 4

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

during the UASB section (0–174 days), which was 65 ± 13%. According to Akram and Stuckey [49] the start-up of anaerobic reactors is characterized by a low methanogenic activity related to the growth of the bacteria involved, which affects the removal of macropollutants and explains the observed results in the first period of this work. However, in the later days, with the aerobic packed bed (from day 188), showed a significant increase, leading to the removal of 99 ± 0.2% of COD which coincides with the maximum OLR value (10.17 kg COD/m3·d). Additional to these results, the hybrid system showed a TS removal of 83 ± 0.54% in the first period. After the aerobic packed stage operation, the removal TS increased to 93 ± 1.03 and 97 ± 2.62% in the last period, considering a TS concentration in the feed of 10.25 g/L. The above is consistent with Liu and Tay [50] where high OLRs maintain a rapid microbial growth, reflected in a greater removal efficiency of macropollutants. In this regard, continuous increments in methanogenic microbial activity indicate the ability of the reactor to continue operated in even higher OLR’s [25]. Nevertheless, reactors treating swine wastewater at high OLR and without a good strategy to operate the system might cause problems such as overloading, acidification risk and therefore process instability [51]. In this work the previous determination of the SMA had a positive impact on the system operation since these increases were made knowing the limitations of the biomass so as not to affect the removal efficiencies of the contaminants. In addition, the statistical analysis showed a significant difference at each OLR increment due to the SMA enhancement. Additionally, the Mexican legal standard indicates that the organic matter content, expressed in terms of biochemical oxygen demand should not exceed the maximum allowed limit of 150 mg/L, applicable to wastewater released into rivers whose water is used for agricultural irrigation [52]. There is no maximum permissible limit for COD in Mexico. However, given that COD is equivalent approximately to 1.33 times the BOD5, the effluent complied with the Mexican standards [3] showing a mean concentration in the last operation period of 84 ± 5 mg /L. Further, the international standards are stricter than those in Mexico. For example, the maximum permissible limit for using wastewater treated in agriculture in Italy is 100 mg/L [53]. Therefore, the COD levels in the effluent of this research would comply with the standard for wastewater reuse in some other countries. Additionally, Fig. 2 (b) shows that the OLR was increased in the hybrid reactor based on the SMA of the biomass previously measured. Yan and Tay [21] recommended an SOLR-SMA ratio of 0.8, which means an increasing of the OLR based on an 80% reduction of biodegradable COD. Accordingly, the OLR value during the first operation period was maintained at 88% of the SMA. This ratio indicating that the system was operating near its maximum load, leading to the conclusion that further increments in OLR without the prior knowledge about the limitation of the biomass, probably have resulted in a sharp increase in volatile fatty acids in the system causing a decrease in the COD removal efficiency. Whereas, in the second period this percentage was 69% and

the SMA showed. Therefore, even it was enough to reduce operational problems like poor sedimentation, washing of the biomass and degranulation. Moreover, the granules of the hybrid reactor could reduce the effect of OLR increase preserving the stability of the system, because of the use of the SMA as a strategy. The OLR is another essential operational condition and allow the mass transfer, preventing the accumulation of microorganisms with low activity, which improves the biogas production and the characteristics of the biomass [36]. In addition, CH4 production in our system was increased from 0.16 to 0.84 L/d when the OLR enhanced from 4.02–10.17 kg DQO/ m3·d. According to Wijekoon et al. [37], this can be attributed to two facts, the increased microbial activity and the increased of organic matter content. Table 2 shows two different SMA values achieved in reactors feeding with swine waste with higher OLR’s than 10 kg DQO/ m3·d, similar to this study. The biggest SMA reported by Rico [38] (0.6 kg COD-CH4/kg VSS·d) in a UASB reactor was achieved as a consequence to operate with an OLR progressive due to the variation of the HRT (3, 2 y 1.5 d), which were two-fold higher than this study. In contrast, Hill and Bolte [39] report a DAF reactor with the same strategy increased the OLR by a reduction of the HRT progressively, obtaining activity values from 0.4 to 0.2 kg COD-CH4/kg VSS·d with HRT´s from 5 to 2 d, respectively. However, the principal difference between the two systems was the acclimation period in the first that could have influenced to achieve a higher value. In addition, SMA test was used to measure the methanogenic activity after carry out changes in the operation of both reactors and not as a previous tool to prevent possible inhibition, as it happened in the DAF system [20]. Currently, limited information is available about the treatment of swine wastewater in integrated hybrid reactors and most of the information reported is on complex systems or operated in different stages [20]. The few studies applicable to the swine waste treatment reported the SMA test is used only as a technique at the start-up of the reactor to measure the quality of the inoculum and not as a periodic control parameter of the system, obtaining a poor performance of the systems as well a very low capacity to tolerate high OLR. As a result, it is necessary to monitor any change in the activities of the methanogenic microorganisms in the anaerobic reactors using available techniques. SMA is attractive because of rapid, reliable results with a low cost to employ as routine analysis. In this study, we observe a positive impact on the anaerobic-aerobic hybrid reactor operation allowing suitable OLR’s applied knowing the limitations of the biomass by SMA analysis so as not to affect the removal efficiencies of the pollutants. 3.2. Operation of the anaerobic-aerobic hybrid reactor The three periods in which the hybrid reactor was operated correspond to increases in OLR, using the previous determination of the SMA as a basis (Eq. 2). Fig. 2(a) shows the average removal efficiency of COD

Fig. 2. (a) Relation between the removal efficiency of COD (▴) and OLR (◇) with the SMA determined in each period of operation, (b) Specific Organic Loading Rate (SOLR)/SMA ratio in each OLR increment; by the hybrid reactor. 5

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

Fig. 3. a) Description of the COD removal efficiency in each OLR (kg COD/ m3·day) and b) Ammonium removal efficiency according to the increases of NH4+-N concentration. Percentage of removal (♦) and OLR or NH4+-N concentration (●).

oxygen is scarce or null, resulting in denitrifying metabolic processes [56]. Table 3 shows a balance of nitrogen species in the hybrid reactor where the NO3−-N produced in the second and third operation period were 49% and 54% of the total at the influent. The results obtained in first generation systems like anaerobic ponds have a removal efficiency of organic matter between 47 and 51% [54]. Conventional reactors such as UASB have removal efficiencies of 70% with an OLR of 4.09 kg COD/m3·d [57] and 57% removal with an OLR of 3.8 kg COD/m3·d [6]. All those examples have lower efficiencies than this study using an OLR higher than 10 kg COD/m3·d. Other authors have reported higher removal efficiencies using more advanced systems than conventional ones. Deng [15] evaluated the treatment of swine wastewater in a combined system of internal circulation anaerobic reactor and sequencing batch reactor (IC-SBR) and obtained removal efficiencies of 95.5% of organic matter and 99.4% of ammoniacal nitrogen, operating with an OLR of 7 kg COD/m3·d and HRT of 5–6 days. However, we observe that this last parameter is superior to the one applied to the hybrid system of this study which was 0.79 ± 0.20 days and that operates with higher loads (10.17 kg COD/m3·d). Shin [58] evaluated the combination of two systems; an anaerobic up-flow bed filter was followed by a submerged membrane bioreactor (AUBF-MBR) to treat swine wastewater. The efficiency of both systems, operating with a maximum OLR of 3 kg COD/m3·d and in a range of Hydraulic Retention Time (HRT) of 1.5–7.8 days, reports a removal of organic matter of 91% whiles for the removal of ammoniacal nitrogen was 60%. It should be noted the hybrid systems operate as uncoupled units while

according to these it was assumed that the hybrid system could be loaded at higher OLRs. Furthermore, in the third operation period, the reactor was at 56% of their capacity, stating the hybrid reactor can operate with OLR higher than 10 kg DQO/m3∙d, in the future. Fig. 3 shows the total COD and ammonium removal efficiencies according with OLR variations. From day 0–188, there was a indeed higher ammonium accumulation (183 ± 104 mg/L) (Fig. 3b) and there are within the typical range of discharges from pig farms [3]. In addition, an increase of ammonium was observed in the effluent of the UASB section of the hybrid reactor, recording an outlet concentration of 253 ± 158 mg NH4+-N/L. This process known as ammonification due to the degradation of organic compounds such as urea, proteins and amino acids from the excreta of pigs and where the final product is the ammonium ion [54]. A similar behavior has been observed in a methanogenic anaerobic system when treating slaughterhouse waste with ammonium concentrations ≤500 mg/L [55]. As a result, of the ammonification, from day 189 an aerobic packed bed section was added to the reactor to increase nitrogen removal, which reached an efficiency of 99.83 ± 0.1% (Fig. 3b). At the end of the hybrid reactor operation, the percentage of nitrogen species in the effluent was 57%. The remaining percentage can be attributed to two phenomena in the packed bed section: i) 11 ± 1% losses by stripping and ii) 30% removed as molecular nitrogen by simultaneous nitrification and denitrification. The latter due to the nitrates produced on the surface of the biomass, which can to penetrate by concentration difference the deeper layers of the biofilm, where

Table 3 Summary of nitrogen balance in anaerobic-aerobic hybrid reactor. Operational periods

I (anaerobic) II III

Final concentration of Nitrogen species (mg/L) Time (days)

TN influent

NH4+-N

NO3−-N

NO2−-N

TN effluent

0-174 175-459 460-500

211 ± 141 146 ± 64 146 ± 6

253 ± 158 20 ± 73 0.8 ± 0

2±1 72 ± 27 79 ± 4

0.4 ± 1 13 ± 27 0.5 ± 4

202 ± 163 83 ± 34 80 ± 4

TN: Total Nitrogen. 6

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

Acknowledgements

the system evaluated in this study is a single unit. In addition, we report the removal process of organic matter carried out in anaerobic digestion and removal of ammonium, by simultaneous nitrification-denitrification in the packed area. The latter, due to the anoxic microzones formed in the biofilm and to nitrification through autotrophic bacteria in suspension [59]. On balance, the hybrid anaerobic-aerobic system technology is a promising solution for swine wastewater treatment due to the compact reactor required, low waste generation and high process efficiency. Accordingly, the anaerobic-aerobic hybrid reactor demonstrated a satisfactory performance operating with OLR superior to those shown in other studies and very short HRT, as well as concentration > 200 mg NH4+-N/L, achieving up to 99% removal of the aforementioned compounds. In agreement with the advantages above mentioned the authors infer that the integrated anaerobic-aerobic hybrid system using the SMA as control parameter might be a good option to treat complex wastewater with a high content of organic matter and decreasing the total nitrogen discharges of the reactor. Some examples of wastewater that can be treat in the hybrid system are from food industry, milk and starch production, sugar processing and brewery with a high COD (> 5000 mg/L) [60]. However, wastewater with low OLR and chemical complexity by the presence of certain compounds as the case of textile wastewater is another option, in which the anaerobic zone could be reduce the azo bond, resulting aromatic amines, that aerobic zone could be completely mineralized by the biofilm and/or suspended bacteria [61]. Finally, the hybrid system could be economically advantageous both on a pilot-scale or large-scale reactor due to the high removal efficiency obtained compared to other systems shown; and which have a highenergy potential by the biogas production from pig waste [62]. Goffi et al. [63] realized an economic feasibility analysis for selecting wastewater treatment systems, thus the hybrid system cost could be inferred. For example, the cost of the energy demand of the anaerobicaerobic system has a maximum cost of $3.50 USD/W·person, lower than aerobic conventional systems. In addition, regarding to cost of land used a UASB + aerated biofilter similar to hybrid system but decoupled, it is up to 90% cheaper than anaerobic ponds commonly used in the swine wastewater treatment, due to its compact design. Furthermore, operation investment of an anaerobic-aerobic system is more economical (26.67 U$D/person) compared with an aerobic system coupled to tertiary treatment ($50.67 USD/person) and a conventional nitrification-denitrification system ($45.33 USD/person).

This work was supported by CONACYT fund Projects of Scientific Development to attend National Problems 2016 [Grand number APN2016-2737] also by PROFAPI _2020. References [1] Instituto Nacional de Estadistica y Geografia, INEGI. Censo Agropecuario. La Porcicultura En Sonora, (2007). [2] J.L. De Victorica-Almeida, M. Galván-García, R. Ayala-Ruiz, Sustainable management of effluents from small piggery farms in Mexico, Am. J. Environ. Sci. 4 (3) (2008) 171–174. [3] M.A. Garzón-Zúñiga, G. Buelna, Caracterización de aguas residuales porcinas y su tratamiento por diferentes procesos en México, Rev. Int. Contam. Ambient. 30 (1) (2014) 65–79. [4] R.A.S. Terán, C. de la, M. Orozco, I.J.G. Acuña, S.G. Rosales, G.D. Araujo, H.O.R. Arias, Emoving organic matter and nutrients from swine wastewater after anaerobic-aerobic treatment, Water (Switzerland) 9 (10) (2017) 1–11. [5] V.H. Techio, J. Stolberg, A. Kunz, E. Zanin, C.C. Perdomo, Genotoxicity of swine effluents, Water Sci. Technol. 63 (5) (2011) 970–976. [6] D. Karakashev, J.E. Schmidt, I. Angelidaki, Innovative process scheme for removal of organic matter, phosphorus and nitrogen from pig manure, Water Res. 42 (15) (2008) 4083–4090. [7] N. Bernet, N. Delgenes, J.C. Akunna, J.P. Delgenes, R. Moletta, Combined anaerobic-aerobic SBR for the treatment of piggery wastewater, Water Res. 34 (2) (2000) 611–619. [8] Y.S. Lee, G.B. Han, Pig slurry treatment by a hybrid multi-stage unit system consisting of an ATAD and an EGSB followed by a SBR reactor, Biosyst. Eng. 111 (3) (2012) 243–250. [9] C. Huang, Y. Shi, J. Xue, Y. Zhang, M. Gamal El-Din, Y. Liu, Comparison of biomass from integrated fixed-film activated sludge (IFAS), moving bed biofilm reactor (MBBR) and membrane bioreactor (MBR) treating recalcitrant organics: importance of attached biomass, J. Hazard. Mater. 326 (2017) 120–129. [10] G. Sunil Kumar, S.K. Gupta, G. Singh, Biodegradation of distillery spent wash in anaerobic hybrid reactor, Water Res. 41 (4) (2007) 721–730. [11] Y.S. Lee, G.B. Han, Pig slurry treatment by a hybrid multi-stage unit system consisting of an ATAD and an EGSB followed by a SBR reactor, Biosyst. Eng. 111 (3) (2012) 243–250. [12] E.H. Ezechi, S.R.M. Kutty, K. Muda, A. Yaqub, J. Water Proc. Eng. A Comp. Eval. Integr. Hybrid Bioreactor Treating Industrial Wastewater 31 (December) (2018) 2019. [13] J. González-lópez, J.M. Poyatos, Anaerobic / Anoxic / Oxic Configuration in Hybrid Moving Bed Biofilm Reactor-Membrane Bioreactor for Nutrient Removal from Municipal Wastewater 91 (2016), pp. 449–458. [14] L. Rodriguez, A.L. Esteban, I. Tejero, Bioresource Technology Comparison between a fixed bed hybrid membrane bioreactor and a conventional membrane bioreactor for municipal wastewater treatment: A pilot-scale study, Bioresour. Technol. 152 (2014) 212–219. [15] L.W. Deng, P. Zheng, Z.A. Chen, Anaerobic digestion and post-treatment of swine wastewater using IC-SBR process with bypass of raw wastewater, Process Biochem. 41 (4) (2006) 965–969. [16] B. Riaño, B. Molinuevo, M.C. García-González, Potential for methane production from anaerobic co-digestion of swine manure with winery wastewater, Bioresour. Technol. 102 (5) (2011) 4131–4136. [17] E. Colleran, F. Concannon, T. Golden, F. Geoghegan, J. Coates, Use of methanogenic activity tests to characterize anaerobic sludges, screen for anaerobic biodegradability and determine toxicity threshold against individual anaerobic trophic groups and species, Sixth Int. Symp. Anaerob. Dig. Sao Paulo, Brazil - 12 - 16 May 1991; Pap. Repr. 25 (4) (1991) 31–40. [18] O. Ince, G.K. Anderson, B. Kasapgil, Control of organic loading rate using the specific methanogenic activity test during start-up of an anaerobic digestion system, Water Res. 29 (1) (1995) 349–355. [19] A. Hussain, S.K. Dubey, Specific methanogenic activity test for anaerobic treatment of phenolic wastewater, Desalin. Water Treat. 52 (37–39) (2014) 7015–7025. [20] A. Hussain, S.K. Dubey, Specific methanogenic activity test for anaerobic degradation of influents, Appl. Water Sci. 7 (2) (2017) 535–542. [21] Y. Yan, S. Engineering, N. Avenue, Characterization of the granulation process during UASB start-up 31 (7) (1997) 1573–1580. [22] A. Hussain, S.K. Dubey, Specific methanogenic activity test for anaerobic degradation of influents, Appl. Water Sci. 7 (2) (2017) 535–542. [23] S. McHugh, M. Carton, G. Collins, V. O’Flaherty, Reactor performance and microbial community dynamics during anaerobic biological treatment of wastewaters at 16-37°C, FEMS Microbiol. Ecol. 48 (3) (2004) 369–378. [24] Y.A. Oktem, O. Ince, P. Sallis, T. Donnelly, B.K. Ince, Anaerobic treatment of a chemical synthesis-based pharmaceutical wastewater in a hybrid upflow anaerobic sludge blanket reactor, Bioresour. Technol. 99 (5) (2008) 1089–1096. [25] K.C. Wijekoon, C. Visvanathan, A. Abeynayaka, Effect of organic loading rate on VFA production, organic matter removal and microbial activity of a two-stage thermophilic anaerobic membrane bioreactor, Bioresour. Technol. 102 (9) (2011) 5353–5360. [26] APHA/AWWA/WEF, American Public Health Association, American Water Works Asso- Ciation, Water Environment Federation (APHA-AWWA-WEF) .2001. Standard

4. Conclusions Integrated anaerobic-aerobic hybrid reactor showed advantage over other schemes with separate units being a feasible technology for treating real swine wastewater. The use of SMA to improve its performance provides a value addition to the hybrid technology maintaining a SOLR-SMA ratio under 0.8 and achieving an adequate stability with an OLR of 10 kg COD/m3·d. Hybrid system complying with current regulations for water bodies discharge, achieving high removal efficiencies of COD (99%) and a complete ammonium elimination (99.8%). The proposal technology could be used for other industrial wastewater with high organic load rates with a possible economic advantage over conventional systems.

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

7

Journal of Water Process Engineering 34 (2020) 101164

P.A. Gonzalez-Tineo, et al.

[27]

[28] [29] [30]

[31]

[32]

[33]

[34]

[35] [36]

[37]

[38]

[39]

[40]

[41]

[42]

[43] [44]

Manag. 71 (2018) 532–541. [45] E.I. Atuanya, M. Aigbirior, Mesophilic Biomethanation and Treatment of Poultry Waste-Water Using Pilot Scale UASB Reactor, Environmental monitoring and assessment, 2002, pp. 139–147. [46] E. Marañón, L. Castrillón, I. Vózquez, H. Sastre, The influence of hydraulic residence time on the treatment of cattle manure in UASB reactors, Waste Manag. Res. 19 (5) (2001) 436–441. [47] D.I. Massé, L. Masse, F. Croteau, The effect of temperature fluctuations on psychrophilic anaerobic sequencing batch reactors treating swine manure, Bioresour. Technol. 89 (1) (2003) 57–62. [48] H.B. Møller, A.M. Nielsen, R. Nakakubo, H.J. Olsen, Process performance of biogas digesters incorporating pre-separated manure, Livest. Sci. 112 (3) (2007) 217–223. [49] A. Akram, D.C. Stuckey, Biomass acclimatisation and adaptation during start-up of a submerged anaerobic membrane bioreactor (SAMBR), Environ. Technol. 29 (10) (2008) 1053–1065. [50] Y. Liu, J.H. Tay, State of the art of biogranulation technology for wastewater treatment, Biotechnol. Adv. 22 (7) (2004) 533–563. [51] N. Duan, et al., Effect of organic loading rate on anaerobic digestion of pig manure: methane production, mass flow, reactor scale and heating scenarios, J. Environ. Manage. 231 (October 2018) (2019) 646–652. [52] SEMARNAT, Normas oficiales mexicanas normas oficiales mexicanas NOM-003SEMARNAT-1997, Conagua (2013) 1–65. [53] G. Wriedt, et al., Water Requirements for Irrigation in the European Union - A Model Based Assessment of Irrigation Water Requirements and Regional Water Demands in Europe EUR 23453 (2008). [54] M.A. Garzón-zúñiga, Mecanismos no convencionales de transformación y remoción del nitrógeno en sistemas de tratamiento de aguas residuales vol. XX, (2005), pp. 137–149. [55] S. Bayr, M. Rantanen, P. Kaparaju, J. Rintala, Mesophilic and thermophilic anaerobic co-digestion of rendering plant and slaughterhouse wastes, Bioresour. Technol. 104 (2012) 28–36. [56] J.P. Bassin, I.N. Dias, S.M.S. Cao, E. Senra, Y. Laranjeira, M. Dezotti, Effect of increasing organic loading rates on the performance of moving-bed biofilm reactors filled with different support media: Assessing the activity of suspended and attached biomass fractions, Process Saf. Environ. Prot. 100 (2016) 131–141. [57] V. Escalante, M. Garzón, S. Valle, Remoción de macronutrientes en el tratamiento de aguas residuales porcinas. vol. 8, (2012), pp. 75–82. [58] J.H. Shin, S.M. Lee, J.Y. Jung, Y.C. Chung, S.H. Noh, Enhanced COD and nitrogen removals for the treatment of swine wastewater by combining submerged membrane bioreactor (MBR) and anaerobic upflow bed filter (AUBF) reactor, Process Biochem. 40 (12) (2005) 3769–3776. [59] P. Pearce, Trickling filters for upgrading low technology wastewater plants for nitrogen removal, Water Sci. Technol. 49 (11–12) (2004) 47–52. [60] G.S. Simate, S.E. Iyuke, S. Ndlovu, M. Heydenrych, The heterogeneous coagulation and flocculation of brewery wastewater using carbon nanotubes, Water Res. 46 (4) (2012) 1185–1197. [61] K. Sarayu, S. Sandhya, Current technologies for biological treatment of textile wastewater-A review, Appl. Biochem. Biotechnol. 167 (3) (2012) 645–661. [62] E. Chan, A. Xia, J.D. Murphy, Can Slurry Biogas Systems Be Cost Effective Without Subsidy in Mexico? 95 (2016), pp. 22–30. [63] A. Goffi, J. Flavio Trojan, D. de Lima, F. Mauro Lizot, M. Trojan, Lizot, S. Thesari, S. Thesari, Economic Feasibility for Selecting Wastewater Treatment Systems, (2019), pp. 1–14.

Methods for the Examination of Water and Wastewater, 22nd Edn 5 (2001), pp. 185–186 Washington, DC. G.K. Anderson, G. Yang, Determination of bicarbonate and total volatile acid concentration in anaerobic digesters using a simple titration, Water Enviroment Res. 64 (February) (1992) 53–59. R.J. Lowry, O.H. Rosebrough, N.J. Farr, A.L. Randall, The folin by oliver, Anal. Biochem. 217 (2) (1951) 220–230. D. Michael, G. K., H. J., R. P, S. Fred, Colorimetric method for determination of sugars and related substances, Anal. Chem. 28 (1956) 350–356. P. Torres, A. Pérez, Á. Cajigas, C. Jurado, N. Ortiz, Seleccion de inoculos para el tratamiento anaerobico de aguas residuales del proceso de extraccion de almidon, Rev. Lasallista Investig. 1 (2007) 8. G.D. Najafpour, A.A.L. Zinatizadeh, A.R. Mohamed, M. Hasnain Isa, H. Nasrollahzadeh, High-rate anaerobic digestion of palm oil mill effluent in an upflow anaerobic sludge-fixed film bioreactor, Process Biochem. 41 (2) (2006) 370–379. F. Omil, P. Lens, L.W. Hulshoff Pol, G. Lettinga, Characterization of biomass from a sulfidogenic, volatile fatty acid-degrading granular sludge reactor, Enzyme Microb. Technol. 20 (3) (1997) 229–236. W. Ben, Z. Qiang, C. Adams, H. Zhang, L. Chen, Simultaneous determination of sulfonamides, tetracyclines and tiamulin in swine wastewater by solid-phase extraction and liquid chromatography-mass spectrometry, J. Chromatogr. A 1202 (2) (2008) 173–180. S.K. Toh, J.H. Tay, B.Y.P. Moy, V. Ivanov, S.T.L. Tay, Size-effect on the physical characteristics of the aerobic granule in a SBR, Appl. Microbiol. Biotechnol. 60 (6) (2003) 687–695. P. Bhunia, M.M. Ghangrekar, Required minimum granule size in UASB reactor and characteristics variation with size, Bioresour. Technol. 98 (5) (2007) 994–999. S. Aiyuk, H. Xu, A. van Haandel, W. Verstraete, Removal of ammonium nitrogen from pretreated domestic sewage using a natural ion exchanger, Environ. Technol. 25 (11) (2004) 1321–1330. K.C. Wijekoon, C. Visvanathan, A. Abeynayaka, Effect of organic loading rate on VFA production, organic matter removal and microbial activity of a two-stage thermophilic anaerobic membrane bioreactor, Bioresour. Technol. 102 (9) (2011) 5353–5360. C. Rico, J.A. Montes, J.L. Rico, Evaluation of different types of anaerobic seed sludge for the high rate anaerobic digestion of pig slurry in UASB reactors, Bioresour. Technol. 238 (2017) 147–156. D.T. Hill, J.P. Bolte, Methane production from low solid concentration liquid swine waste using conventional anaerobic fermentation, Bioresour. Technol. 74 (3) (2000) 241–247. O. Ince, M. Kolukirik, N.A. Oz, B.K. Ince, Comparative evaluation of full-scale UASB reactors treating alcohol distillery wastewaters in terms of performance and methanogenic activity, J. Chem. Technol. Biotechnol. 80 (2) (2005) 138–144. S. McHugh, G. Collins, T. Mahony, V. O’Flaherty, Biofilm reactor technology for low temperature anaerobic waste treatment: microbiology and process characteristics, Water Sci. Technol. 52 (7) (2005) 107–113. J. Ho, S. Sung, Methanogenic activities in anaerobic membrane bioreactors (AnMBR) treating synthetic municipal wastewater, Bioresour. Technol. 101 (7) (2010) 2191–2196. X. Song, K. Zhang, B. Han, J. Liang, Z. Zhai, L. Du, Anaerobic Co-digestion of pig manure with dried maize straw, BioResources 11 (4) (2016) 8914–8928. C. Dennehy, et al., Anaerobic co-digestion of pig manure and food waste; effects on digestate biosafety, dewaterability, and microbial community dynamics, Waste

8