- Email: [email protected]
aerobic system
Desalination 253 (2010) 158–163
Contents lists available at ScienceDirect
Desalination j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / d e s a l
Treatment of high strength wastewater from fruit juice industry using integrated anaerobic/aerobic system Hala El-Kamah a, Ahmed Tawfik a, Mohamed Mahmoud a,⁎, Hisham Abdel-Halim b a b
Water Pollution Research Department, National Research Centre, Cairo, Egypt Faculty of Engineering, Cairo University, Cairo, Egypt
a r t i c l e
i n f o
Article history: Received 23 September 2009 Received in revised form 9 November 2009 Accepted 10 November 2009 Available online 5 December 2009 Keywords: Fruit juice industry UASR Activated sludge process Agricultural reuse
a b s t r a c t This work aimed to study the treatment of wastewater generated from fruit juice industry (24–30 m3/batch). Three treatment schemes have been investigated. The first treatment scheme was a batch activated sludge (AS) system and was operated at different aeration time up to 48 h. The second scheme was two-stage upflow anaerobic sponge reactors (UASRs). Two-stage UASRs were operated at a total hydraulic retention time (HRT) of 13 h corresponding to an organic loading rate (OLR) of 8.7 kg COD/m3 d. While, the third treatment scheme consisted of a two-stage UASR followed by an AS system which was operated at three different HRTs namely 10, 12, and 14 h. Long term experiments indicated the superiority of the third treatment scheme which operated at a total HRT of 23 h (UASRs: 13 h and AS: 10 h) in terms of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total suspended solids (TSS) and oil & grease removal. The integrated system achieved an overall removal efficiency of 97.5% for COD, 99.2% for BOD5, 94.5% for TSS and 98.9% for oil & grease. The treated wastewater produced from the UASR–AS system complied with the standards set by the Egyptian law regulating the reuse of treated wastewater in agricultural purposes. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Food-processing industries in Egypt are under increasing pressure to reduce the impact of their wastewater streams on the environment. The production of large volumes of untreated wastewater can thus become a very serious financial burden. Most of the wastewater generated from food industries is highly contaminated with organic matter, dissolved solids, suspended solids and oil & grease [1]. Wastewater must be properly treated to the degree necessary to comply with the regulatory standards for discharge into surface water or reuse for agricultural application [2,3]. Anaerobic digestion technology has been applied for treatment of a wide variety of industrial wastewaters with high organic matter content, including dairy wastewater [4], cheese whey wastewater [5], distillery spent wash water [6], starch wastewater [7], and slaughterhouse wastewater [8]. The up-flow anaerobic sludge bed (UASB) reactor technology is considered a breakthrough in the development and application of anaerobic high-rate technology for industrial wastewater especially for wastewaters coming from food-processing industries [9]. Problems with the UASB reactor treating wastewater result from washout of biomass which deteriorates the effluent quality [10]. In the anaerobic biofilm reactors, the support medium acts as a physical pro⁎ Corresponding author. Tel./fax: + 20 2 33351573. E-mail addresses: [email protected] (H. El-Kamah), [email protected] (M. Mahmoud). 0011-9164/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2009.11.013
tective factor against washout, thus being potentially attractive for biomass retention in the reactor. El-Gohary et al. [11] compared between classical UASB and anaerobic hybrid reactor (AHR) for the treatment of pre-treated catalytically oxidized olive mill wastewater (OMW) at an HRT of 24 h and an OLR of 2 kg COD/m3 d. After reaching the steady state, the AHR removed 64% of the COD which was higher by 14% than that obtained in the UASB reactor. In this study, the polyurethane foam was used as packing media and randomly distributed in anaerobic reactors to: (i) improve the solids– microbial contact, and even the contact between the solids and the extracellular enzymes, (ii) overcome washout of suspended solids, (iii) enhance hydrolysis of the particulate organic matter, (iv) increase the sludge residence time (SRT), and reduces the applied hydraulic retention time. However, the effluent of the anaerobic reactors generally does not comply with standards for discharge into receiving water bodies. Therefore, post-treatment is required. Malaspina et al. [12] investigated the integrated system consisting of down-flow–up-flow hybrid reactor (DUHR) followed by sequencing batch reactor (SBR) as post-treatment system for treatment of dairy wastewater. The whole system achieved more than 90% removal of COD, nitrogen and phosphorus. In another study, Wahaab and El-Awady [13] investigated the feasibility of using rotating biological contactors (RBC) as post-treatment system for treatment of pre-anaerobically meat processing wastewater. RBC was operated at an OLR of 0.288 kg BOD5/m2 d. RBC system achieved a substantial reduction of COD, BOD5, TSS and oil & grease resulting effluent quality with residual values of 132, 40, 44 and 10 mg/L, respectively.
H. El-Kamah et al. / Desalination 253 (2010) 158–163
This work presents a feasibility study for the treatment of wastewater generated from fruit juice industry. The factory produces natural concentrated syrups of different fruits (Apple, Orange, Cherry etc.). Wastewater generated from the factory varied from 24 to 30 m3/batch. Wastewater is characterized by high BOD5 and COD values representing their high organic content. These effluents may cause serious problems, in terms of organic load on the local sewerage system. Therefore, appropriate treatment is required prior to reuse treated effluent in irrigation purposes [14]. So, the aim of this research work was to investigate a simple, low-cost integrated system for treatment of high strength fruit juice wastewater to produce treated wastewater complies with the national regulatory standards for reuse in agricultural application. 2. Materials and methods In this study, three treatment schemes have been designed and manufactured. The first scheme was an activated sludge (AS) system. The second scheme was a two-stage up-flow anaerobic sponge reactor (UASR). While, the third one was a two-stage UASR followed by an AS system. The three schemes were located out-door and were operated at a temperature of 25 °C. A schematic block diagram of the experimental layout is shown in Fig. 1. 2.1. The first treatment scheme The activated sludge (AS) system used in this experiment was a batch scale complete mixed reactor model. The bioreactor system was made from glass with a working volume of 2 L. The bioreactor was initially inoculated with 1 L biomass. The used biomass (3.6 g VSS/L and SVI of 62 mL/g TSS) was taken from a near-by full scale activated sludge plant treating domestic wastewater (Zeneen, Cairo). AS system was aerated through an air diffuser, under these conditions the dissolved oxygen concentration in the reactor was kept between 2 and 3 mg/L. To attain the acclimated state, the AS system was fed twice a day with a mixture of domestic and industrial wastewater for 1 week. This was followed by 2 weeks of operation using the raw industrial wastewater. After reaching the acclimated state, the AS system was fed with 1 L of raw wastewater and then 100 mL of the mixed liquor was taken from the AS system at a different aeration time. The mixed liquor was allowed to settle for 1 h, and then the supernatant was withdrawn and analyzed to determine the optimum contact time from COD removal standpoint. This experiment was repeated six times.
159
shaped bottom and gas solid separator (GSS). The UASR had a height of 70 cm, and an internal diameter of 10 cm (Fig. 2). Each reactor was seeded with sludge obtained from the pilot plant anaerobic hybrid reactor treating municipal wastewater [15]. The sludge had a concentration of 22 g/L for total solids at 105 °C, 13.6 g/L for volatile solids at 550 °C and 44.5 mL/gTS for SVI. The total amount of sludge added to the reactor was approximately 2 L which represented 40% of the total reactor volume. The floating polyurethane foam was used as packing media and was randomly distributed in the anaerobic reactors. The dimensions of the used sponge (cylindrical shape) amounted to 27 mm in height× 22 mm in diameter. The polyurethane material used in this study was supported by a polypropylene plastic material with fins. The sponge characteristics parameters were surface area (256 m2/m3), density (30 kg/m3), void ratio (0.9), and pore size (0.63 mm). The total amount of sponge added to the reactor was approximately 1.5 L. The UASRs were operated at a total HRT of 13 h, throughout the study. OLR's varied from 5.49 to 15.5 kg COD/m3 d with an average value of 8.7 kg COD/m3 d. During start-up, the reactor was operated at 25 °C with a total HRT of 24 h to allow sludge adaptation to fruit juice wastewater. Afterwards, the HRT was gradually shortened with the corresponding increase in organic load to reach the desired HRT (13 h). For calculating the SRT of the UASRs, it is assumed that the effluent VSS had the same SRT as the excess sludge. The SRT of the UASRs were calculated according to Eq. (1).
SRT =
V ⋅X Qw ⋅ Xw + Q ⋅ Xe
ð1Þ
where V is the reactor volume (L), X is the average sludge concentration in the reactor (g VSS/L), Q w is the excess sludge (L/d), Xw is the concentration of the excess sludge (g VSS/L), Q is the wastewater flow rate (L/d), and Xe is VSS concentration in the effluent (g VSS/L). 2.3. The third treatment scheme The UASRs effluent (pre-treated effluent) was subjected directly into an activated sludge system as post-treatment step. To attain the acclimated state, the AS system was fed twice a day with a mixture of domestic and industrial wastewater for 1 week. After reaching the acclimated state, the AS system was fed continuously with the anaerobic effluent and was operated at three different HRTs namely, 10, 12 and 14 h.
2.2. The second treatment scheme
2.4. Fruit juice wastewater
This experiment was carried out using a two-identical-stage UASR. UASRs were manufactured from PVC and were connected in series. Each UASR (5 L) consisted of a cylindrical column with a conical
The end of pipe effluent used in this study was collected from a fruit juice factory. The wastewater that was generated from the factory varied from 24 to 30 m3/batch. Wastewater was mainly produced from production lines, equipments and floor cleaning operations. Fruit juice wastewater contains a relatively high biodegradable organic matter (BOD5/COD ratio = 0.61). The pH of the raw wastewater was slightly acidic. So, to provide buffering capacity, 1.5–2 mol of bicarbonate was added to ensure that the wastewater pH did not drop below 7.4 [16,17]. 2.5. Sample collection and analysis
Fig. 1. Schematic block diagram of the proposed treatment schemes.
The performance of the treatment schemes was monitored by implementing an extensive sampling and analysis program. Samples from influent and effluent of each treatment step were collected for analyses. The analyses covered: pH-value, chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total suspended solids (TSS), total kjeldahl nitrogen (TKN), total phosphorous (Total-P), sulfate, hydrogen sulfide and oil & grease. The raw sample was used for COD and BOD5, and a 0.45 µm membrane filtered the samples for soluble COD and BOD5, respectively. The particulate COD and BOD5 were calculated by the
160
H. El-Kamah et al. / Desalination 253 (2010) 158–163
Fig. 2. Two-stage up-flow anaerobic sponge reactors (UASRs).
difference between COD and CODsoluble, and BOD5 and BOD5 soluble, respectively. Moreover, sludge characteristics including: sludge volume, total solids, volatile solids and sludge volume index were also carried out. All analyses were carried out according to APHA [18]. 2.6. Kinetics modeling The kinetics modeling used in this study was based on basic Monod model. Two limiting cases of the Monod model were considered. 2.6.1. Zero order model In the cases of constant biomass concentrations with low biomass change, i.e., ΔX ≪ X0, and high substrate concentration (S ≫ Ks), Monod equation can be reduced to a zero order reaction [19]: dS = kX : dt
ð2Þ
Therefore, the kinetics constants “kX” can be measured by zero order linear regression using substrate S versus time plot, with the slope being equal to the product of “k” and X. Thus “k” is the slope of the zero order coefficient versus biomass concentration (X). 2.6.2. First order model On the other hand, based on the same constant biomass concentration condition, with Ks ≫ S, Monod equation can be simplified to a first order reaction: dS kXS = dt Ks
ð3Þ
Therefore, the first order biodegradation kinetics coefficient “kX/Ks” can be determined from ln(S /S0) versus time plot. The slope of the first order biodegradation coefficient versus biomass is thus k /Ks. 2.7. Engineering studies Based on the results of treatability study, engineering design related to final recommendations was carried out. Preparation of preliminary cost estimation for the suggested scheme was conducted.
3. Results and discussion 3.1. Wastewater characteristics The characteristics of the investigated wastewater are presented in (Table 1). Available data indicates great fluctuations in the strength of the wastewater during the study period; this could be due to variations in the production processes. COD varied from 2280 to 10,913 mg/L with an average value of 5157 mg/L. Corresponding BOD5 varied from 1650 to 6900 mg/L with an average concentration of 3134 mg/L. The average TSS and oil & grease concentrations were 323 mg/L and 74 mg/L, respectively.
3.2. Treatment schemes 3.2.1. The first treatment scheme The temporal variation of COD in the batch scale operated with fruit juice wastewater at initial substrate to microorganism ratio of 1.11 mg COD/mg VSS is depicted in Fig. 3. As apparent from Fig. 3, COD removal was accomplished within 30 h, and no further reduction in Table 1 Mean characteristics of the fruit juice wastewater. Parameters
Unit
Min
Max.
Average ⁎
pH-value COD CODsoluble BOD5 BOD5 soluble TSS (105 °C) VSS (550 °C) TDS (105 °C) TKN Total phosphorous Oil & grease⁎⁎
– mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
5.4 2280 1900 1650 1080 118 14 2304 38.0 4.6 18.0 72 0.0 0.1 80
8 10,913 2875 6900 1620 1534.0 580 17,918 252 20.8 717.8 214 20.0 4.4 1000
– 5157 ± 2897 2429 ± 401 3134 ± 1546 1289 ± 261 323 ± 349 183 ± 152.4 5483 ± 3941 58.2 ± 59 10.2 ± 5.3 74 ± 180 144.3 ± 59 10.7 ± 9 1.03 ± 1.5 260 ± 271
Sulfate Hydrogen sulfide Iron Chloride
⁎ An average of 20 samples. ⁎⁎ Oil & grease and all extractable matter by chloroform.
H. El-Kamah et al. / Desalination 253 (2010) 158–163
161
Fig. 3. COD batch removal kinetics.
COD was observed after that, with the steady state COD stabilizing at 30–50 mg/L. Furthermore, the results of this test clearly show that COD removal efficiencies ranged from 10 to 99.5% with about 1% of the initial COD was non-biodegradable even after 30 h of treatment. This is to be excepted since any organic loading above the maximum microbial uptake will be untreated. As elaborated upon earlier, both limiting cases of the Monod model i.e., zero order and first order kinetics were investigated. A summary of the zero order and first order coefficients for the various batches is listed in Table 2 together with the various correlation coefficients. Fig. 4 illustrates graphically the fit of the data from the batch AS system to the first order kinetic model. It is apparent from the data that the first order kinetic model fit the data well; with an R2 value of 0.921 from the first order kinetics. The reasonably good fit of the data to the first order model approximations may be explained by a varying biomass concentration or prevalence of wide values in substrate concentrations within the vicinity of this Ks value in any given batch. The results presents in Fig. 5 show that by increasing HRT from 28 to 30 h, the COD, BOD5 and TSS concentrations in the final effluent significantly dropped from 175 to 30, 38 to 8 and 82 to 36 mg/L, respectively. However, further removal of COD and BOD5 did not occur by increasing the HRT to 48 h. On the other hand, TSS concentrations in the final effluent significantly dropped from 36 to 5 mg/L by increasing HRT from 30 to 48 h to produce effluent with quality complying with the national allowable limits which regulate the reuse of treated wastewater in agricultural purposes (COD = 80 mg/L, BOD5 = 60 mg/L and TSS = 50 mg/L). This excellent performance towards the removal of organic matter can be attributed to the high active biomass present in the system. Moreover, the results also clearly demonstrate that the activated sludge system can produce an effluent quality containing low concentration of TSS. The suspended matter could be adsorbed on and/or enmeshed into the biomass and then hydrolyzed by extra-cellular enzymes [12]. Sludge analyses showed that, the sludge volume index ranged from 50 to 83 mL/gTS which gives an indication for the good settle ability of sludge. Microscopic examination of the sludge indicated the presence of many colonies of protozoa, especially stalked ciliates such as Vorticella, Opercularia and Rotatoria (not shown).
3.2.2. The second treatment scheme The two-stage UASRs were operated at a total constant HRT of 13 h, throughout the study. OLR's varied from 5.49 to 15.5 kg COD/ m3 d with an average value of 8.7 kg COD/m3 d due to a change in the
Fig. 4. Zero order COD removal kinetics (a); first order COD removal kinetics (b).
influent composition. Despite variations in OLR, the reactors provided effluent quality of around 2033 mg/L for COD, and 910 mg/L for BOD5 corresponding to the percentage removal values of 61 and 70%, respectively (Fig. 6a). Also the results clearly show that, a substantial reduction of TSS was achieved resulting in an average percentage removal of 69%. This indicates the high efficiency of the UASRs for the removal of suspended solids at a relatively high suspended solids loading rate of 0.8 kg TSS/m3 d. This relatively good performance could be attributed to the long sludge residence time (SRT = 76 d) which would effectively increase the efficiency of hydrolysis and subsequent digestion of organic matter. In this investigation, COD removal was lower than that previously reported for UASB reactor treating cheese production wastewater at a lower OLR (1.5–1.9 kg COD/m3 d) and substantially longer HRT (30–40 h) [20] and also lower than those obtained from the UASB reactor treating dairy wastewater at an OLR ranging from 2.4 to 13.5 kg COD/m3 d and shorter HRT of 3 h. The COD removal ranged from 61 to 95.6% [4]. The adsorption phenomena play an important role for COD and TSS removal which occurs in anaerobic treatment of complex fat containing effluents, it is acceptable to assume that in an anaerobic reactor, the sludge bed acts as a filter retaining the organic matter which leads to the growth of sludge [21]. Once the storage capacity is exhausted, unintentional washout of the sludge together with the effluent takes place. This indicates that the sludge bed of the anaerobic reactor had lost its adsorption or retention capacity originating a breakthrough phenomenon similar to that common in an adsorption column. In this study, the washout of biomass did not occur; this was due to the use of floating polyurethane foam at the top portion of the reactor.
Table 2 Kinetics of zero order and first order modeling. Batch
Fruit juice wastewater
Zero order kinetics
First order kinetics
k′ (kX) (mg/L d)
R2
K″ (kX / Ks) (L/d)
R2
1657.75
0.6297
2.764
0.921
Fig. 5. AS system's performance for fruit juice wastewater treatment at different HRTs.
162
H. El-Kamah et al. / Desalination 253 (2010) 158–163
increased. The residual values in the AS effluent at HRT of 14, 12 and 10 h were 21, 50 and 65 mg/L for COD; 10, 10 and 16 mg/L for BOD5 and 3, 5 and 15 mg/L for TSS, respectively (Fig. 7a). The results presented in Fig. 7b show no significant improvement in the removal efficiency of Total-P and TKN by increasing the HRT. These results are comparable to the results obtained by Malaspina et al. [12] who used a sequencing batch reactor for treatment of the anaerobic down-flow–up-flow hybrid reactor effluent and activated sludge system treating the anaerobic reactor effluent [25]. Over 90% of COD was removed at a sludge age of 20 days. Consequently, residual values of the pollution parameters in the final effluent of the anaerobic–aerobic system complied with the national allowable limit which regulates the reuse of wastewater for irrigation purposes. 3.3. Cost estimation of the proposed wastewater treatment plant
Fig. 6. Concentrations of COD, BOD5 and TSS (a); TKN, Total-P and oil &grease (b) in fruit juice wastewater and UASRs effluent.
Residual total phosphorous, TKN and oil &grease in the treated effluent were 9.1, 28.4 and 21.6 mg/L corresponding to average percentage removal of 11, 51 and 70%, respectively (Fig. 6b). Apparently, the removal of phosphorous and nitrogen was due to precipitation, while the removal of oil and grease was due to entrapment/adsorption to the sludge bed of the UASB reactor [22]. The characteristics of the retained and excess sludge from the twostage UASRs are presented in Table 3. The VS/TS ratio of wasted sludge was 0.66 which indicates that the wasted sludge was almost stabilized. The mean value of the net sludge yield coefficient was found to be 0.2 g VSS/g COD removed per day, corresponding to 20% of the total influent COD. This is a very important feature of the UASR, since it is significantly lower than that normally found in conventional aerobic systems. Sludge production in the UASRs may be attributed to flocculation of non-biodegradable particulate matter, forming the inert sludge mass fraction and the biological sludge mass that is generated as a result of anaerobic conversion in the UASR [23,24].
In most developing countries, industrial wastewater treatment and disposal is a matter of concern that needs to be addressed. The prospects for economic and social development, poverty and priorities for industrial investments are the main obstacles in making decisions about wastewater facilities. Since financing, constructing, operation and maintenance of wastewater treatment plants are quite costly, most developing countries [26] including Egypt, avoid these projects. Based on the above results, the preliminary cost estimation for a fruit juice wastewater treatment plant was conducted. Fig. 8 shows the schematic diagram of the proposed system, which consists of: two-stage UASRs as pre-treatment step followed by an AS step. The fixed capital cost was 1,554,000 LE. The values shown are based on the available market prices of 2009 for similar works. The work shall comprise supply of all materials, construction of civil work, and supply and erection of all mechanical and electrical equipments. While the annual operation and maintenance (O&M) cost including electrical energy cost, labor cost, insurance cost... etc. was 100,000 LE. 4. Conclusion and recommendation In this study, three treatment schemes have been manufactured and studied for the treatment of fruit juice wastewater. The first
3.2.3. The third treatment scheme The effluent quality of the anaerobic step does not meet the standards set regulating the reuse of treated wastewater in agricultural purposes. Therefore, the activated sludge system has been investigated as a posttreatment for the UASRs effluent. The AS system was operated at three different HRTs namely, 10, 12 and 14 h. The obtained results show that by increasing the HRT from 10 to 14 h the removal efficiency of COD, BOD5 and TSS in the AS system
Table 3 Characteristics of the retained and excess sludge from UASRs. Parameters
Unit
Sludge volume Total solids at 105 °C Volatile solids at 105 °C VS/TS Sludge volume index (SVI) Sludge production Sludge yield coefficient Sludge residence time (SRT)
mL/L 980 ± 142 g/L 28 ± 12 g/L 18 ± 9 – 0.64 ± 0.18 mL/g TSS 35 ± 12 g VSS/d – g VSS/g COD removed⋅d d –
Retained sludge
Excess sludge 55 ± 23 0.6 ± 0.2 0.4 ± 0.15 0.66 ± 0.2 91.6 ± 23 2.0 ± 0.8 0.2 76
Fig. 7. Concentrations of COD, BOD5 and TSS (a); TKN and Total-P (b) Concentrations of TKN and Total-P in AS effluent treating UASRs effluent.
H. El-Kamah et al. / Desalination 253 (2010) 158–163
163
Fig. 8. Schematic diagram of the proposed treatment system.
scheme consists of an AS system. The second scheme is a two-stage UASR. While, the third one is a two-stage UASR as a pre-treatment followed by an AS system. Based on the available results, the following conclusions were drawn: (1) The two-stage UASR is an efficient technique for the pretreatment of fruit juice wastewater at an HRT of 13 h. The reactor achieved percentage removal values of 61% for COD, 70% for BOD5, 69% for TSS, 51% for TKN, 11% for Total-P and 70% for oil & grease. (2) The wasted sludge from the UASR reactor was almost stabilized (VS/TS ratio = 0.66). The sludge yield coefficient was around 0.2 g VSS/g COD totally removed per day, corresponding to 20% of the total influent COD. Moreover, the use of polyurethane foam as a packing media sheets overcome the washout out of biomass which occur in a classical UASB reactor. (3) The combination of the two-stage UASR and the AS system represents a very promising option for the treatment of juice industry wastewater. The combined system achieved an average removal efficiency of 97.5% for COD, 99.2% for BOD5, 94.5% for TSS and 98.9% for oil & grease. The effluent quality of the integrated anaerobic/aerobic system complies with the national allowable standards required for reuse in agricultural purposes. (4) Accordingly, the proposed system can thus be recommended as a techno-economically feasible fruit juice wastewater treatment system.
Acknowledgements The technical support provided by K. Abdel Wahad, F. Rifaat, H. Hegazy and A. Nasr is gratefully acknowledged.
References [1] L. Guerrero, F. Omil, R. Mendez, J.M. Lema, Water Res. 33 (1999) 3281–3290. [2] Metcalf & Eddy, Inc. (4th Ed.), Wastewater engineering: Treatment and reuse, McGraw-Hill, New York, 2003. [3] WHO, Health guidelines for the use of wastewater in agriculture and aquaculture. Technical report series No. 778. Geneva, 1989. [4] E.V. Ramasamy, S. Gajalakshmi, R. Sanjeevi, M.N. Jithesh, S.A. Abbasi, Biores. Technol. 93 (2004) 209–212. [5] S.V. Kalyuzhnyi, E. Perez Martinez, J. Rodriguez Martinez, Biores. Technol. 60 (1997) 59–65. [6] C.B. Shivayogimath, T.K. Ramanujam, Bioprocess Eng. 21 (1999) 255–259. [7] B.K. Rajbhandari, A.P. Annachhatre, Biores. Technol. 95 (2004) 135–143. [8] R. Borja, C.J. Banks, Z. Wang, A. Mancha, Biores. Technol. 65 (1998) 125–133. [9] J.B. Van Lier, Proc. of ACHEMA 2006, 28th Int. Exhibition Conference on Chemical Technology, Environmental Protection and Biotechnology. May 15–19, Frankfurt, Germany, 2006. [10] A. Rinzema, M. Boone, K. van Knippenberg, G. Lettinga, Water Env. Res. 66 (1994) 40–49. [11] F. El-Gohary, A. Tawfik, M. Badawy, M.A. El-Khateeb, Biores. Technol. 100 (2009) 2147–2154. [12] F. Malaspina, L. Stante, C.M. Cellamare, A. Tilche, Water Sci. Technol. 32 (1995) 59–72. [13] R.A. Wahaab, M.H. El-Awady, The Environmentalist 19 (1999) 61–65. [14] N. Benet, E. Paul, in: F.J. Cervantres, S.G. Pavlostathis, A.C. Van Haandel (Eds.), IWA Publishing, London, 2006, pp. 237–266. [15] M. Mahmoud, A. Tawfik, F. Samhan, F. El-Gohary, Desal. Water Treat. 4 (2009) 168–176. [16] S. Rebac, J.B. Van Lier, P. Lens, A.J. Stams, F. Dekkers, K.T. Swinkels, G. Lettinga, Water Sci. Technol. 39 (1999) 203–210. [17] Z. Xu, G. Nakhla, J. Chem. Technol. Biotechnol. 81 (2006) 580–587. [18] Standard Methods for the Examination of Water and Wastewater, 21st Ed., American Public Health Association, Washington, DC, 2005. [19] V.A. Vavilin, L.Y. Lokshina, Biores. Technol. 1 (1996) 69–80. [20] H.N. Gavala, H. Kopsinis, I.V. Skiadas, K. Stamatelatou, G.L. Lyberatos, J. Agric. Eng. Res. 73 (1999) 59–63. [21] H. Nadais, I. Capela, L. Arroja, A. Duarte, Water Res. 39 (2005) 1511–1518. [22] B. Vinneras, PhD Thesis, Swedish University of Agricultural Sciences, Uppsala, 2002. [23] K.Y. Show, J.H. Tay, Water Res. 33 (1999) 1471–1481. [24] D. Orhon, G. Yildiz, E.U. Cokgor, S. Sozen, Water Sci. Technol. 32 (1995) 11–19. [25] M.J. Donkin, J.M. Russell, Water Sci. Technol. 36 (1997) 79–86. [26] H.A. Bakir, J. Env. Manag. 61 (2001) 319–328.
Contents lists available at ScienceDirect
Desalination j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / d e s a l
Treatment of high strength wastewater from fruit juice industry using integrated anaerobic/aerobic system Hala El-Kamah a, Ahmed Tawfik a, Mohamed Mahmoud a,⁎, Hisham Abdel-Halim b a b
Water Pollution Research Department, National Research Centre, Cairo, Egypt Faculty of Engineering, Cairo University, Cairo, Egypt
a r t i c l e
i n f o
Article history: Received 23 September 2009 Received in revised form 9 November 2009 Accepted 10 November 2009 Available online 5 December 2009 Keywords: Fruit juice industry UASR Activated sludge process Agricultural reuse
a b s t r a c t This work aimed to study the treatment of wastewater generated from fruit juice industry (24–30 m3/batch). Three treatment schemes have been investigated. The first treatment scheme was a batch activated sludge (AS) system and was operated at different aeration time up to 48 h. The second scheme was two-stage upflow anaerobic sponge reactors (UASRs). Two-stage UASRs were operated at a total hydraulic retention time (HRT) of 13 h corresponding to an organic loading rate (OLR) of 8.7 kg COD/m3 d. While, the third treatment scheme consisted of a two-stage UASR followed by an AS system which was operated at three different HRTs namely 10, 12, and 14 h. Long term experiments indicated the superiority of the third treatment scheme which operated at a total HRT of 23 h (UASRs: 13 h and AS: 10 h) in terms of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total suspended solids (TSS) and oil & grease removal. The integrated system achieved an overall removal efficiency of 97.5% for COD, 99.2% for BOD5, 94.5% for TSS and 98.9% for oil & grease. The treated wastewater produced from the UASR–AS system complied with the standards set by the Egyptian law regulating the reuse of treated wastewater in agricultural purposes. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Food-processing industries in Egypt are under increasing pressure to reduce the impact of their wastewater streams on the environment. The production of large volumes of untreated wastewater can thus become a very serious financial burden. Most of the wastewater generated from food industries is highly contaminated with organic matter, dissolved solids, suspended solids and oil & grease [1]. Wastewater must be properly treated to the degree necessary to comply with the regulatory standards for discharge into surface water or reuse for agricultural application [2,3]. Anaerobic digestion technology has been applied for treatment of a wide variety of industrial wastewaters with high organic matter content, including dairy wastewater [4], cheese whey wastewater [5], distillery spent wash water [6], starch wastewater [7], and slaughterhouse wastewater [8]. The up-flow anaerobic sludge bed (UASB) reactor technology is considered a breakthrough in the development and application of anaerobic high-rate technology for industrial wastewater especially for wastewaters coming from food-processing industries [9]. Problems with the UASB reactor treating wastewater result from washout of biomass which deteriorates the effluent quality [10]. In the anaerobic biofilm reactors, the support medium acts as a physical pro⁎ Corresponding author. Tel./fax: + 20 2 33351573. E-mail addresses: [email protected] (H. El-Kamah), [email protected] (M. Mahmoud). 0011-9164/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2009.11.013
tective factor against washout, thus being potentially attractive for biomass retention in the reactor. El-Gohary et al. [11] compared between classical UASB and anaerobic hybrid reactor (AHR) for the treatment of pre-treated catalytically oxidized olive mill wastewater (OMW) at an HRT of 24 h and an OLR of 2 kg COD/m3 d. After reaching the steady state, the AHR removed 64% of the COD which was higher by 14% than that obtained in the UASB reactor. In this study, the polyurethane foam was used as packing media and randomly distributed in anaerobic reactors to: (i) improve the solids– microbial contact, and even the contact between the solids and the extracellular enzymes, (ii) overcome washout of suspended solids, (iii) enhance hydrolysis of the particulate organic matter, (iv) increase the sludge residence time (SRT), and reduces the applied hydraulic retention time. However, the effluent of the anaerobic reactors generally does not comply with standards for discharge into receiving water bodies. Therefore, post-treatment is required. Malaspina et al. [12] investigated the integrated system consisting of down-flow–up-flow hybrid reactor (DUHR) followed by sequencing batch reactor (SBR) as post-treatment system for treatment of dairy wastewater. The whole system achieved more than 90% removal of COD, nitrogen and phosphorus. In another study, Wahaab and El-Awady [13] investigated the feasibility of using rotating biological contactors (RBC) as post-treatment system for treatment of pre-anaerobically meat processing wastewater. RBC was operated at an OLR of 0.288 kg BOD5/m2 d. RBC system achieved a substantial reduction of COD, BOD5, TSS and oil & grease resulting effluent quality with residual values of 132, 40, 44 and 10 mg/L, respectively.
H. El-Kamah et al. / Desalination 253 (2010) 158–163
This work presents a feasibility study for the treatment of wastewater generated from fruit juice industry. The factory produces natural concentrated syrups of different fruits (Apple, Orange, Cherry etc.). Wastewater generated from the factory varied from 24 to 30 m3/batch. Wastewater is characterized by high BOD5 and COD values representing their high organic content. These effluents may cause serious problems, in terms of organic load on the local sewerage system. Therefore, appropriate treatment is required prior to reuse treated effluent in irrigation purposes [14]. So, the aim of this research work was to investigate a simple, low-cost integrated system for treatment of high strength fruit juice wastewater to produce treated wastewater complies with the national regulatory standards for reuse in agricultural application. 2. Materials and methods In this study, three treatment schemes have been designed and manufactured. The first scheme was an activated sludge (AS) system. The second scheme was a two-stage up-flow anaerobic sponge reactor (UASR). While, the third one was a two-stage UASR followed by an AS system. The three schemes were located out-door and were operated at a temperature of 25 °C. A schematic block diagram of the experimental layout is shown in Fig. 1. 2.1. The first treatment scheme The activated sludge (AS) system used in this experiment was a batch scale complete mixed reactor model. The bioreactor system was made from glass with a working volume of 2 L. The bioreactor was initially inoculated with 1 L biomass. The used biomass (3.6 g VSS/L and SVI of 62 mL/g TSS) was taken from a near-by full scale activated sludge plant treating domestic wastewater (Zeneen, Cairo). AS system was aerated through an air diffuser, under these conditions the dissolved oxygen concentration in the reactor was kept between 2 and 3 mg/L. To attain the acclimated state, the AS system was fed twice a day with a mixture of domestic and industrial wastewater for 1 week. This was followed by 2 weeks of operation using the raw industrial wastewater. After reaching the acclimated state, the AS system was fed with 1 L of raw wastewater and then 100 mL of the mixed liquor was taken from the AS system at a different aeration time. The mixed liquor was allowed to settle for 1 h, and then the supernatant was withdrawn and analyzed to determine the optimum contact time from COD removal standpoint. This experiment was repeated six times.
159
shaped bottom and gas solid separator (GSS). The UASR had a height of 70 cm, and an internal diameter of 10 cm (Fig. 2). Each reactor was seeded with sludge obtained from the pilot plant anaerobic hybrid reactor treating municipal wastewater [15]. The sludge had a concentration of 22 g/L for total solids at 105 °C, 13.6 g/L for volatile solids at 550 °C and 44.5 mL/gTS for SVI. The total amount of sludge added to the reactor was approximately 2 L which represented 40% of the total reactor volume. The floating polyurethane foam was used as packing media and was randomly distributed in the anaerobic reactors. The dimensions of the used sponge (cylindrical shape) amounted to 27 mm in height× 22 mm in diameter. The polyurethane material used in this study was supported by a polypropylene plastic material with fins. The sponge characteristics parameters were surface area (256 m2/m3), density (30 kg/m3), void ratio (0.9), and pore size (0.63 mm). The total amount of sponge added to the reactor was approximately 1.5 L. The UASRs were operated at a total HRT of 13 h, throughout the study. OLR's varied from 5.49 to 15.5 kg COD/m3 d with an average value of 8.7 kg COD/m3 d. During start-up, the reactor was operated at 25 °C with a total HRT of 24 h to allow sludge adaptation to fruit juice wastewater. Afterwards, the HRT was gradually shortened with the corresponding increase in organic load to reach the desired HRT (13 h). For calculating the SRT of the UASRs, it is assumed that the effluent VSS had the same SRT as the excess sludge. The SRT of the UASRs were calculated according to Eq. (1).
SRT =
V ⋅X Qw ⋅ Xw + Q ⋅ Xe
ð1Þ
where V is the reactor volume (L), X is the average sludge concentration in the reactor (g VSS/L), Q w is the excess sludge (L/d), Xw is the concentration of the excess sludge (g VSS/L), Q is the wastewater flow rate (L/d), and Xe is VSS concentration in the effluent (g VSS/L). 2.3. The third treatment scheme The UASRs effluent (pre-treated effluent) was subjected directly into an activated sludge system as post-treatment step. To attain the acclimated state, the AS system was fed twice a day with a mixture of domestic and industrial wastewater for 1 week. After reaching the acclimated state, the AS system was fed continuously with the anaerobic effluent and was operated at three different HRTs namely, 10, 12 and 14 h.
2.2. The second treatment scheme
2.4. Fruit juice wastewater
This experiment was carried out using a two-identical-stage UASR. UASRs were manufactured from PVC and were connected in series. Each UASR (5 L) consisted of a cylindrical column with a conical
The end of pipe effluent used in this study was collected from a fruit juice factory. The wastewater that was generated from the factory varied from 24 to 30 m3/batch. Wastewater was mainly produced from production lines, equipments and floor cleaning operations. Fruit juice wastewater contains a relatively high biodegradable organic matter (BOD5/COD ratio = 0.61). The pH of the raw wastewater was slightly acidic. So, to provide buffering capacity, 1.5–2 mol of bicarbonate was added to ensure that the wastewater pH did not drop below 7.4 [16,17]. 2.5. Sample collection and analysis
Fig. 1. Schematic block diagram of the proposed treatment schemes.
The performance of the treatment schemes was monitored by implementing an extensive sampling and analysis program. Samples from influent and effluent of each treatment step were collected for analyses. The analyses covered: pH-value, chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total suspended solids (TSS), total kjeldahl nitrogen (TKN), total phosphorous (Total-P), sulfate, hydrogen sulfide and oil & grease. The raw sample was used for COD and BOD5, and a 0.45 µm membrane filtered the samples for soluble COD and BOD5, respectively. The particulate COD and BOD5 were calculated by the
160
H. El-Kamah et al. / Desalination 253 (2010) 158–163
Fig. 2. Two-stage up-flow anaerobic sponge reactors (UASRs).
difference between COD and CODsoluble, and BOD5 and BOD5 soluble, respectively. Moreover, sludge characteristics including: sludge volume, total solids, volatile solids and sludge volume index were also carried out. All analyses were carried out according to APHA [18]. 2.6. Kinetics modeling The kinetics modeling used in this study was based on basic Monod model. Two limiting cases of the Monod model were considered. 2.6.1. Zero order model In the cases of constant biomass concentrations with low biomass change, i.e., ΔX ≪ X0, and high substrate concentration (S ≫ Ks), Monod equation can be reduced to a zero order reaction [19]: dS = kX : dt
ð2Þ
Therefore, the kinetics constants “kX” can be measured by zero order linear regression using substrate S versus time plot, with the slope being equal to the product of “k” and X. Thus “k” is the slope of the zero order coefficient versus biomass concentration (X). 2.6.2. First order model On the other hand, based on the same constant biomass concentration condition, with Ks ≫ S, Monod equation can be simplified to a first order reaction: dS kXS = dt Ks
ð3Þ
Therefore, the first order biodegradation kinetics coefficient “kX/Ks” can be determined from ln(S /S0) versus time plot. The slope of the first order biodegradation coefficient versus biomass is thus k /Ks. 2.7. Engineering studies Based on the results of treatability study, engineering design related to final recommendations was carried out. Preparation of preliminary cost estimation for the suggested scheme was conducted.
3. Results and discussion 3.1. Wastewater characteristics The characteristics of the investigated wastewater are presented in (Table 1). Available data indicates great fluctuations in the strength of the wastewater during the study period; this could be due to variations in the production processes. COD varied from 2280 to 10,913 mg/L with an average value of 5157 mg/L. Corresponding BOD5 varied from 1650 to 6900 mg/L with an average concentration of 3134 mg/L. The average TSS and oil & grease concentrations were 323 mg/L and 74 mg/L, respectively.
3.2. Treatment schemes 3.2.1. The first treatment scheme The temporal variation of COD in the batch scale operated with fruit juice wastewater at initial substrate to microorganism ratio of 1.11 mg COD/mg VSS is depicted in Fig. 3. As apparent from Fig. 3, COD removal was accomplished within 30 h, and no further reduction in Table 1 Mean characteristics of the fruit juice wastewater. Parameters
Unit
Min
Max.
Average ⁎
pH-value COD CODsoluble BOD5 BOD5 soluble TSS (105 °C) VSS (550 °C) TDS (105 °C) TKN Total phosphorous Oil & grease⁎⁎
– mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
5.4 2280 1900 1650 1080 118 14 2304 38.0 4.6 18.0 72 0.0 0.1 80
8 10,913 2875 6900 1620 1534.0 580 17,918 252 20.8 717.8 214 20.0 4.4 1000
– 5157 ± 2897 2429 ± 401 3134 ± 1546 1289 ± 261 323 ± 349 183 ± 152.4 5483 ± 3941 58.2 ± 59 10.2 ± 5.3 74 ± 180 144.3 ± 59 10.7 ± 9 1.03 ± 1.5 260 ± 271
Sulfate Hydrogen sulfide Iron Chloride
⁎ An average of 20 samples. ⁎⁎ Oil & grease and all extractable matter by chloroform.
H. El-Kamah et al. / Desalination 253 (2010) 158–163
161
Fig. 3. COD batch removal kinetics.
COD was observed after that, with the steady state COD stabilizing at 30–50 mg/L. Furthermore, the results of this test clearly show that COD removal efficiencies ranged from 10 to 99.5% with about 1% of the initial COD was non-biodegradable even after 30 h of treatment. This is to be excepted since any organic loading above the maximum microbial uptake will be untreated. As elaborated upon earlier, both limiting cases of the Monod model i.e., zero order and first order kinetics were investigated. A summary of the zero order and first order coefficients for the various batches is listed in Table 2 together with the various correlation coefficients. Fig. 4 illustrates graphically the fit of the data from the batch AS system to the first order kinetic model. It is apparent from the data that the first order kinetic model fit the data well; with an R2 value of 0.921 from the first order kinetics. The reasonably good fit of the data to the first order model approximations may be explained by a varying biomass concentration or prevalence of wide values in substrate concentrations within the vicinity of this Ks value in any given batch. The results presents in Fig. 5 show that by increasing HRT from 28 to 30 h, the COD, BOD5 and TSS concentrations in the final effluent significantly dropped from 175 to 30, 38 to 8 and 82 to 36 mg/L, respectively. However, further removal of COD and BOD5 did not occur by increasing the HRT to 48 h. On the other hand, TSS concentrations in the final effluent significantly dropped from 36 to 5 mg/L by increasing HRT from 30 to 48 h to produce effluent with quality complying with the national allowable limits which regulate the reuse of treated wastewater in agricultural purposes (COD = 80 mg/L, BOD5 = 60 mg/L and TSS = 50 mg/L). This excellent performance towards the removal of organic matter can be attributed to the high active biomass present in the system. Moreover, the results also clearly demonstrate that the activated sludge system can produce an effluent quality containing low concentration of TSS. The suspended matter could be adsorbed on and/or enmeshed into the biomass and then hydrolyzed by extra-cellular enzymes [12]. Sludge analyses showed that, the sludge volume index ranged from 50 to 83 mL/gTS which gives an indication for the good settle ability of sludge. Microscopic examination of the sludge indicated the presence of many colonies of protozoa, especially stalked ciliates such as Vorticella, Opercularia and Rotatoria (not shown).
3.2.2. The second treatment scheme The two-stage UASRs were operated at a total constant HRT of 13 h, throughout the study. OLR's varied from 5.49 to 15.5 kg COD/ m3 d with an average value of 8.7 kg COD/m3 d due to a change in the
Fig. 4. Zero order COD removal kinetics (a); first order COD removal kinetics (b).
influent composition. Despite variations in OLR, the reactors provided effluent quality of around 2033 mg/L for COD, and 910 mg/L for BOD5 corresponding to the percentage removal values of 61 and 70%, respectively (Fig. 6a). Also the results clearly show that, a substantial reduction of TSS was achieved resulting in an average percentage removal of 69%. This indicates the high efficiency of the UASRs for the removal of suspended solids at a relatively high suspended solids loading rate of 0.8 kg TSS/m3 d. This relatively good performance could be attributed to the long sludge residence time (SRT = 76 d) which would effectively increase the efficiency of hydrolysis and subsequent digestion of organic matter. In this investigation, COD removal was lower than that previously reported for UASB reactor treating cheese production wastewater at a lower OLR (1.5–1.9 kg COD/m3 d) and substantially longer HRT (30–40 h) [20] and also lower than those obtained from the UASB reactor treating dairy wastewater at an OLR ranging from 2.4 to 13.5 kg COD/m3 d and shorter HRT of 3 h. The COD removal ranged from 61 to 95.6% [4]. The adsorption phenomena play an important role for COD and TSS removal which occurs in anaerobic treatment of complex fat containing effluents, it is acceptable to assume that in an anaerobic reactor, the sludge bed acts as a filter retaining the organic matter which leads to the growth of sludge [21]. Once the storage capacity is exhausted, unintentional washout of the sludge together with the effluent takes place. This indicates that the sludge bed of the anaerobic reactor had lost its adsorption or retention capacity originating a breakthrough phenomenon similar to that common in an adsorption column. In this study, the washout of biomass did not occur; this was due to the use of floating polyurethane foam at the top portion of the reactor.
Table 2 Kinetics of zero order and first order modeling. Batch
Fruit juice wastewater
Zero order kinetics
First order kinetics
k′ (kX) (mg/L d)
R2
K″ (kX / Ks) (L/d)
R2
1657.75
0.6297
2.764
0.921
Fig. 5. AS system's performance for fruit juice wastewater treatment at different HRTs.
162
H. El-Kamah et al. / Desalination 253 (2010) 158–163
increased. The residual values in the AS effluent at HRT of 14, 12 and 10 h were 21, 50 and 65 mg/L for COD; 10, 10 and 16 mg/L for BOD5 and 3, 5 and 15 mg/L for TSS, respectively (Fig. 7a). The results presented in Fig. 7b show no significant improvement in the removal efficiency of Total-P and TKN by increasing the HRT. These results are comparable to the results obtained by Malaspina et al. [12] who used a sequencing batch reactor for treatment of the anaerobic down-flow–up-flow hybrid reactor effluent and activated sludge system treating the anaerobic reactor effluent [25]. Over 90% of COD was removed at a sludge age of 20 days. Consequently, residual values of the pollution parameters in the final effluent of the anaerobic–aerobic system complied with the national allowable limit which regulates the reuse of wastewater for irrigation purposes. 3.3. Cost estimation of the proposed wastewater treatment plant
Fig. 6. Concentrations of COD, BOD5 and TSS (a); TKN, Total-P and oil &grease (b) in fruit juice wastewater and UASRs effluent.
Residual total phosphorous, TKN and oil &grease in the treated effluent were 9.1, 28.4 and 21.6 mg/L corresponding to average percentage removal of 11, 51 and 70%, respectively (Fig. 6b). Apparently, the removal of phosphorous and nitrogen was due to precipitation, while the removal of oil and grease was due to entrapment/adsorption to the sludge bed of the UASB reactor [22]. The characteristics of the retained and excess sludge from the twostage UASRs are presented in Table 3. The VS/TS ratio of wasted sludge was 0.66 which indicates that the wasted sludge was almost stabilized. The mean value of the net sludge yield coefficient was found to be 0.2 g VSS/g COD removed per day, corresponding to 20% of the total influent COD. This is a very important feature of the UASR, since it is significantly lower than that normally found in conventional aerobic systems. Sludge production in the UASRs may be attributed to flocculation of non-biodegradable particulate matter, forming the inert sludge mass fraction and the biological sludge mass that is generated as a result of anaerobic conversion in the UASR [23,24].
In most developing countries, industrial wastewater treatment and disposal is a matter of concern that needs to be addressed. The prospects for economic and social development, poverty and priorities for industrial investments are the main obstacles in making decisions about wastewater facilities. Since financing, constructing, operation and maintenance of wastewater treatment plants are quite costly, most developing countries [26] including Egypt, avoid these projects. Based on the above results, the preliminary cost estimation for a fruit juice wastewater treatment plant was conducted. Fig. 8 shows the schematic diagram of the proposed system, which consists of: two-stage UASRs as pre-treatment step followed by an AS step. The fixed capital cost was 1,554,000 LE. The values shown are based on the available market prices of 2009 for similar works. The work shall comprise supply of all materials, construction of civil work, and supply and erection of all mechanical and electrical equipments. While the annual operation and maintenance (O&M) cost including electrical energy cost, labor cost, insurance cost... etc. was 100,000 LE. 4. Conclusion and recommendation In this study, three treatment schemes have been manufactured and studied for the treatment of fruit juice wastewater. The first
3.2.3. The third treatment scheme The effluent quality of the anaerobic step does not meet the standards set regulating the reuse of treated wastewater in agricultural purposes. Therefore, the activated sludge system has been investigated as a posttreatment for the UASRs effluent. The AS system was operated at three different HRTs namely, 10, 12 and 14 h. The obtained results show that by increasing the HRT from 10 to 14 h the removal efficiency of COD, BOD5 and TSS in the AS system
Table 3 Characteristics of the retained and excess sludge from UASRs. Parameters
Unit
Sludge volume Total solids at 105 °C Volatile solids at 105 °C VS/TS Sludge volume index (SVI) Sludge production Sludge yield coefficient Sludge residence time (SRT)
mL/L 980 ± 142 g/L 28 ± 12 g/L 18 ± 9 – 0.64 ± 0.18 mL/g TSS 35 ± 12 g VSS/d – g VSS/g COD removed⋅d d –
Retained sludge
Excess sludge 55 ± 23 0.6 ± 0.2 0.4 ± 0.15 0.66 ± 0.2 91.6 ± 23 2.0 ± 0.8 0.2 76
Fig. 7. Concentrations of COD, BOD5 and TSS (a); TKN and Total-P (b) Concentrations of TKN and Total-P in AS effluent treating UASRs effluent.
H. El-Kamah et al. / Desalination 253 (2010) 158–163
163
Fig. 8. Schematic diagram of the proposed treatment system.
scheme consists of an AS system. The second scheme is a two-stage UASR. While, the third one is a two-stage UASR as a pre-treatment followed by an AS system. Based on the available results, the following conclusions were drawn: (1) The two-stage UASR is an efficient technique for the pretreatment of fruit juice wastewater at an HRT of 13 h. The reactor achieved percentage removal values of 61% for COD, 70% for BOD5, 69% for TSS, 51% for TKN, 11% for Total-P and 70% for oil & grease. (2) The wasted sludge from the UASR reactor was almost stabilized (VS/TS ratio = 0.66). The sludge yield coefficient was around 0.2 g VSS/g COD totally removed per day, corresponding to 20% of the total influent COD. Moreover, the use of polyurethane foam as a packing media sheets overcome the washout out of biomass which occur in a classical UASB reactor. (3) The combination of the two-stage UASR and the AS system represents a very promising option for the treatment of juice industry wastewater. The combined system achieved an average removal efficiency of 97.5% for COD, 99.2% for BOD5, 94.5% for TSS and 98.9% for oil & grease. The effluent quality of the integrated anaerobic/aerobic system complies with the national allowable standards required for reuse in agricultural purposes. (4) Accordingly, the proposed system can thus be recommended as a techno-economically feasible fruit juice wastewater treatment system.
Acknowledgements The technical support provided by K. Abdel Wahad, F. Rifaat, H. Hegazy and A. Nasr is gratefully acknowledged.
References [1] L. Guerrero, F. Omil, R. Mendez, J.M. Lema, Water Res. 33 (1999) 3281–3290. [2] Metcalf & Eddy, Inc. (4th Ed.), Wastewater engineering: Treatment and reuse, McGraw-Hill, New York, 2003. [3] WHO, Health guidelines for the use of wastewater in agriculture and aquaculture. Technical report series No. 778. Geneva, 1989. [4] E.V. Ramasamy, S. Gajalakshmi, R. Sanjeevi, M.N. Jithesh, S.A. Abbasi, Biores. Technol. 93 (2004) 209–212. [5] S.V. Kalyuzhnyi, E. Perez Martinez, J. Rodriguez Martinez, Biores. Technol. 60 (1997) 59–65. [6] C.B. Shivayogimath, T.K. Ramanujam, Bioprocess Eng. 21 (1999) 255–259. [7] B.K. Rajbhandari, A.P. Annachhatre, Biores. Technol. 95 (2004) 135–143. [8] R. Borja, C.J. Banks, Z. Wang, A. Mancha, Biores. Technol. 65 (1998) 125–133. [9] J.B. Van Lier, Proc. of ACHEMA 2006, 28th Int. Exhibition Conference on Chemical Technology, Environmental Protection and Biotechnology. May 15–19, Frankfurt, Germany, 2006. [10] A. Rinzema, M. Boone, K. van Knippenberg, G. Lettinga, Water Env. Res. 66 (1994) 40–49. [11] F. El-Gohary, A. Tawfik, M. Badawy, M.A. El-Khateeb, Biores. Technol. 100 (2009) 2147–2154. [12] F. Malaspina, L. Stante, C.M. Cellamare, A. Tilche, Water Sci. Technol. 32 (1995) 59–72. [13] R.A. Wahaab, M.H. El-Awady, The Environmentalist 19 (1999) 61–65. [14] N. Benet, E. Paul, in: F.J. Cervantres, S.G. Pavlostathis, A.C. Van Haandel (Eds.), IWA Publishing, London, 2006, pp. 237–266. [15] M. Mahmoud, A. Tawfik, F. Samhan, F. El-Gohary, Desal. Water Treat. 4 (2009) 168–176. [16] S. Rebac, J.B. Van Lier, P. Lens, A.J. Stams, F. Dekkers, K.T. Swinkels, G. Lettinga, Water Sci. Technol. 39 (1999) 203–210. [17] Z. Xu, G. Nakhla, J. Chem. Technol. Biotechnol. 81 (2006) 580–587. [18] Standard Methods for the Examination of Water and Wastewater, 21st Ed., American Public Health Association, Washington, DC, 2005. [19] V.A. Vavilin, L.Y. Lokshina, Biores. Technol. 1 (1996) 69–80. [20] H.N. Gavala, H. Kopsinis, I.V. Skiadas, K. Stamatelatou, G.L. Lyberatos, J. Agric. Eng. Res. 73 (1999) 59–63. [21] H. Nadais, I. Capela, L. Arroja, A. Duarte, Water Res. 39 (2005) 1511–1518. [22] B. Vinneras, PhD Thesis, Swedish University of Agricultural Sciences, Uppsala, 2002. [23] K.Y. Show, J.H. Tay, Water Res. 33 (1999) 1471–1481. [24] D. Orhon, G. Yildiz, E.U. Cokgor, S. Sozen, Water Sci. Technol. 32 (1995) 11–19. [25] M.J. Donkin, J.M. Russell, Water Sci. Technol. 36 (1997) 79–86. [26] H.A. Bakir, J. Env. Manag. 61 (2001) 319–328.