Desalination 198 (2006) 16–23
Removal of organic compounds from municipal landfill leachate in a membrane bioreactor Michał Bodzek*, Ewa Łobos-Moysa, Marlena Zamorowska Silesian University of Technology, ul. Konarskiego 18, 44-100 Gliwice, Poland Tel./fax: +48 (32) 237-2368; email:
[email protected] Received 3 November 2005; Accepted 13 December 2005
Abstract Landfill leachate is highly loaded, toxic and is bad for the sanitation of wastewater. The management of leachate can be carried out by applying treatment or pre-treatment, recirculation (spraying), evaporation to the solid phase and discharge into sewer systems or transfer to a wastewater treatment plant. Research is presented into the biodegradation of leachate collected from the municipal landfill in Gliwice, which was added to a medium that simulated municipal wastewater. The tests were carried out in two systems: a laboratory bioreactor with activated sludge and a membrane bioreactor. The biodegradation of organic compounds was assessed on the basis of reduction in the contaminants denoted by BOD, COD, TOC and changes in IC. The results revealed a considerable impact of the amount of added leachate (2.5, 5 and 10%) on the effectiveness of biodegradation. The application of membrane operations instead of the conventional secondary tank enhanced the treatment of wastewater that contained municipal landfill leachate. Keywords: Membrane bioreactor; Biodegradation; Landfill leachate
1. Introduction Leachate is generated in landfill sites by hydrolysis processes (products of biochemical changes in organic substances) or is the result of *Corresponding author.
water penetration, e.g., rain through deposited waste [1,2]. It is extremely difficult to render it harmless due to its qualitative and quantitative composition. Leachate is composed of large amounts of both organic and inorganic compounds, and their concentration depends to the age of a landfill site
Presented at the 2nd Membrane Science and Technology Conference of Visegrad Countries (PERMEA), Polanica Zdroj, Poland, 18–22 September 2005. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.09.004
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[1,3–5]. Organic compounds are usually present in fresh waste. The successive phases of biodegradation during waste deposition cause a reduction in COD and BOD, and the only substances left in the leachate are scarcely biodegradable compounds. COD and BOD may differ depending on the age of the landfill: 23,800 mg/dm3 (fresh waste), 1,160 mg/dm3 (old waste) and 11,900 mg/dm3, 260 mg/dm3, respectively [1]. For biogenic elements, e.g., ammonium nitrogen, the concentration may range from 20 to 2000 mg/dm3 [3]. Leachate also contains AOX compounds regarded as harmful due to their toxic properties and accumulation in the environment [2,5]. Leachate is a hazard to sanitation. The number of E. coli and Streptococcus organisms, e.g., is estimated to be 106–107 per 100 cm3 (during the summer months) [1,4]. Their penetration into the ground poses a serious hazard to natural waters [6,7]. Leachate can be managed in a landfill site in many ways: treatment or pre-treatment, recirculation (spraying) in the site to speed up the process of waste methanation and evaporation of leachate to the solid phase using biogas [2–4,8, 9]. It can also be discharged into a sewer system or transferred to a wastewater treatment plant. There are various technologies used to treat it, but unfortunately, some of them are costly. The physicochemical processes worth mentioning are: evaporation, sedimentation, adsorption on activated carbon, coagulation, ion exchange and membrane operations which can be used solely or in combination with other processes. Oxygenation might be recommended as one of the chemical processes [2,3,10–18]. Membrane processes combined with biological ones, e.g., activated sludge and RO [19], NF [20] and UF [21–23], or UF and RO [24], as well as biomass adsorbed on activated carbon and UF [25], have been used to treat this type of highly loaded wastewater. The treatment of leachate with high COD (3,000 mg/dm3) and low BOD5
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(450 mg/dm3) by means of an activated sludge system produced a COD removal of 69%. The addition of NF increased the efficiency up to 71% [20]. The retentate (concentrate) from the membrane module was recirculated to raw wastewater through the reactors with chemical oxygenation and activated carbon. The addition of successive membrane operations to biological treatment offered new advantages [24]. The UF membrane initially separated the treated leachate from activated sludge which was recirculated into the bioreactor. Then, the leachate was directed to RO modules where inorganic compounds and non-biodegradable organic ones were removed, and the permeate of suitable composition could be discharged into surface waters. Its volume was approximately 70–80% of leachate flux. RO concentrate was evaporated and dried (the resultant waste constituted 1–2% of leachate weight) or was transferred back to the landfill site. The process was intensified by pre-treating the leachate by means of coagulation or sedimentation [25]. The removal of COD, TOC and BOD ranged from 8.5–13%. The subsequent use of adsorbed biomass and UF resulted in a further reduction from 95 to 97%. The process of UF retained bacteria and viruses as well. 2. Materials and methods 2.1. Objective The study aimed to treat municipal wastewater with an addition of landfill leachate and to assess the influence of the increasing dosages of leachate on biodegradation. 2.2. Medium The leachate was collected at the municipal landfill site situated in the southeast of Gliwice, approximately 4 km away from the city center. The amount of waste deposited in the 32-ha
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landfill site reaches 75,000 tons annually. The old part whose area is 11 ha is being recultivated and the new one’s capacity is estimated to be 1.9 Mm3 of waste. The new landfill site was constructed according to EU standards and is equipped with numerous installations and facilities such as a leachate pumping station, retention reservoir, drainage and girdling ditch, disinfection tank, biogas power plant, waste compactors, loading machines and bulldozers. The properly formed and secured substratum (thickened, drainage of ground waters in the sand-gravel layer, foil, drainage of leachate in the sand layer, tires) allows the collection of leachate which is subsequently pumped into the retention reservoir. Part of the leachate is recirculated to the landfill to ensure proper humidity of the waste, while the remaining part is discharged into the sewer system. The leachate collected in spring and summer was used as a 2.5–10% addition to prepare model wastewater which contained an easily accessible source of carbon and macro- and microelements (NH4Cl, CaCl2·H2O, MgSO4·7H2O). 2.3. Apparatus and procedures The tests were carried our under aerobic conditions using the activated sludge system in a laboratory bioreactor equipped with a secondary tank and membrane bioreactor. The total capacity of both installations was 19 dm3. The 0.015 m2 tubular UF membranes used were made of polysulfone. Their efficiency was 4.3×10!5 m3/m2·s at 0.02 MPa during distilled water filtration and 1.5×10!5 m3/m2·s during leachate filtration. The membrane retention of COD and BOD from the leachate was 50% and 54%, respectively. The first step of the research involved culturing activated sludge in the aerobic bioreactor under flow conditions for 30 days. During that time, the bioreactor was fed with medium only. The experimental results provided a basis for
determining the characteristics of activated sludge. Leachate biodegradation in the bioreactor was in the range of substrate loadings of 0.22– 0.37 gBOD/gTS×d, gradually adding leachate (2.5, 5 and 10%) to the model medium. The process enabled the formation of a specific mixed population of activated sludge which contained bacteria and coexisting organisms. As far as the membrane bioreactor is concerned, only the 10% addition of leachate and the loading of 0.2 gBOD/gTS×d were used. The effectiveness of the process in both installations was assessed on the basis of the following results: BOD (OxiTop, WTW), COD (SQ 118 spectrophotometer, Merck), total carbon, inorganic carbon and organic carbon (multiN/C, Analityc Jena) and absorbance at 254 nm (Cecil 1000 spectrophotometer, ABA Analytical). 3. Results and discussion 3.1. Biodegradation of leachate by activated sludge The biodegradation of model wastewater prepared from an enriched medium (without any additions) resulted in a decrease in BOD in the effluent down to 10–20 mgO2/dm3 (Fig. 1). It corresponded to an efficiency of 94.6% to 90.2%. The introduction of 2.5% volumetric addition of landfill leachate on the fifth day, then 5% on the eighth day did not bring about marked changes in the quality of the effluent and effectiveness of the process. Significant differences, however, were observed after adding the 10% dosage on the 22nd day. BOD in the effluent differed markedly from 10 to 100 mgO2/dm3 affecting the biodegradation efficiency which varied greatly from 96% to 58%. The concentration of TOC and inorganic carbon (IC) in the bioreactor effluent ranged from 11.5 to 24.6 mgTOC/dm3 (efficiency from 88.9% to 76.1%) and 55 mg IC/dm3 (on average), respectively (Figs. 2 and 3). Slight changes in the
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Fig. 1. Correlation of BOD, its removal and municipal leachate dosage.
Fig. 2. Correlation of TOC concentration, its removal and municipal leachate dosage.
quality of the effluent started at a 5% dosage. The changes increased with an increasing amount of leachate in the wastewater, i.e., TOC concentration at the 2.5% and 5% additions ranged from 21.7 mg/dm3 (77.6%) to 29.9 mg/dm3 (82%),
while at the 10% addition it displayed a wide range of 30.6 mg/dm3 (78.2%) to 86.2 mg/dm3 (47.9%). IC concentration in the effluent at the leachate dosages ranged from 43.1 to 47 mg/dm3 and 52 to 159.5 mg/dm3, respectively.
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Fig. 3. Correlation of IC concentration and municipal leachate dosage.
Fig. 4. BOD values in treated wastewater and its removal during particular hours of MB operation at 10 % dosage of municipal leachate and loading of 0.2 gBOD/gTS×d
It was concluded that a longer contact time between the microorganisms in the activated sludge and the wastewater with the 10% addition of municipal landfill leachate might result in a population which would be more resistant to the contaminants specific to the leachate, and the effectiveness, though lower, would not be so wide.
3.2. Leachate biodegradation by activated sludge in a membrane bioreactor The combination of several individual processes of high efficiency enhanced the effectiveness of the wastewater treatment. The application of the membrane bioreactor with activated sludge increased the efficiency of the biodegradation of the wastewater with a 10% addition of leachate up to 98.3% (BOD) (Fig. 4), while the average
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Fig. 5. TOC and IC concentration in treated wastewater and TOC removal during particular hours of MB operation at a 10% dosage of municipal leachate and a loading of 0.2 gBOD/ gTS×d. Table 1 Changes in the concentrations of organic compounds in wastewater with a 10% addition of municipal landfill leachate during treatment in a membrane bioreactor at a loading of 0.2 gBOD/ gTS×d Parameters
Raw wastewater
Treated wastewater
Removal [%]
In bioreactora
BOD [mgO2/dm3] COD [mgO2/dm3] TOC [mg/dm3] Absorbance at 254 nm
290 442 127 0.795
5 78 32.2 0.386
98.3 82.4 74.7 —
90 190 45 0.822
a
Sample from bioreactor.
efficiency for the bioreactor with a secondary settling tank was only 80%. The membrane bioreactor also produced a stable quality of the effluent (after the system stabilized) i.e., 5 mgO2/dm3. Simultaneously, no accumulation of the contaminants (BOD) in the bioreactor was observed since they were retained on the membrane. Similar effects were found for TOC (Fig. 5). Its concentration in the effluent of the membrane bioreactor was 32.2 mg TOC/dm3 on average; after 12 h of tank operation the value dropped from 87.7 to 45 mg TOC/dm3. For IC, the values
were 62.6 and 69.4 mg IC/dm3, respectively. They were lower than the ones obtained even after 20 days of treatment of wastewater with the 10% addition of leachate in the activated sludge bioreactor equipped with a secondary settling tank, i.e., from 47.7 to 57.6 mg TOC/dm3 and from 76.4 to 94 mg IC/dm3. Table 1 shows the average values for BOD, COD, TOC and contaminants denoted as UV absorbance at 254 nm in raw and treated wastewater, and the values observed after 12 h in the sample filtered from the bioreactor.
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Fig. 6. Effect of loading and methods applied on the effectiveness of leachate-enriched wastewater treatment.
3.3. Effect of activated sludge loading and leachate dosage on changes in the effectiveness of wastewater treatment The investigation into the influence of landfill leachate dosage on wastewater biodegradation with respect to the contamination loading of activated sludge revealed that the higher contribution of leachate (10%) in wastewater reduced the efficiency of the process (Fig. 6.). It also ranged widely with increasing loading, i.e., from 58.3% to 95.9%. A similar correlation was not found for the model wastewater nor for smaller leachate dosages (2.5% and 5%). The loadings of 0.22– 0.37 gBOD/gTS×d produced an efficiency of 89.7–96.4%. Small amounts of leachate (2.5 and 5%) added to domestic sewage may be successfully treated in a municipal wastewater treatment plant; however, larger additions substantially impair the efficiency of the process. In that case, more effective technologies are recommended. The application of a membrane bioreactor produces better results, i.e., approximately 98.3% at 0.2 gBOD/gTS×d. 4. Conclusions It is concluded that municipal landfill leachate might significantly affect biodegradation. Its
large additions result in changes of the technological parameters of wastewater treatment plants, and in the case of plants being designed, other technologies such as membrane operations should be considered. References [1] M. Żygadłó, Municipal Waste Management, Kielce University of Technology Press, Kielce, 1998 (in Polish). [2] M. Bodzek, J. Surmacz-Górska and Y.-T. Hung, Treatment of landfill leachate, in: Handbook of Industrial and Hazardous Wastes Treatment, L.K. Wang, Y.-T. Hung, H.H. Lo and C. Yapijakis, eds., Marcel Dekker, New York, 2004, pp. 1155–1208. [3] J. Oleszkiewicz, Exploitation of Waste Landfills. Handbook, Lemprojekt, Kraków, 1999 (in Polish). [4] St. Łuniewski, Bezpieczne składowanie odpadów, Ekonomia i Środowisko, Białystok, 2000 (in Polish). [5] B. Gade, M. Layh, H. Westermann and N. Amsoneit, Determination of organic parameters in water and laechates from the hazardius waste landfill of Rainndorf, Germany. Water Mng. Res., 14 (1996) 553–569. [6] Y. Abu-Rukah and O. Al-Kofahi, The assessment of the effect of landfill leachate on ground-water quality — a case study. El-Akader landfill site — north Jordan. J. Arid Environ., 49 (1991) 615–630. [7] P. Kjeldsen, P.L. Bjerg, P. Rügger, J.K. Pedersen, B. Skov, A. Foverskov and Th.H. Christensen,
M. Bodzek et al. / Desalination 198 (2006) 16–23
[8] [9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
Assessment of the spatial variability in leachate migration from an old landfill site. Inter. J. Rock Mechanics Mining Sci. Geomechanics Abstracts, 32(7) (1995) 313 A. F.G. Pohland, Landfill bioreactors: fundamentals and practice. Water Q. Inter., 9–10 (1996) 18–22. D.R. Reihart and A. Basel Al-Yousfi, The impact of leachate recirculation on municipal solid waste landfill operating characteristics. Waste Mngmt. Res., 14 (1996) 337–346. B. Bilitewski, G, Härdtle and K. Marek, Handbook of Waste Management, Seidel-Przywecki, Warsaw, 2003 (in Polish). J. Surmacz-Górska, Degradation of organics compounds in municipal landfill leachates, Environmental Engineering Committee of the Polish Academy of Science, No. 5, Lublin, 2001 (in Polish). A.A. Tatsi, A.I. Zouboulis, K.A. Matis and P. Samaras, Coagulation–flocculation pretreatment of sanitary landfill leachates. Chemosphere, 53 (2003) 737–744. J. Rodriguez, L. Castrillon, E. Maranon, H. Sastre and E. Fernandez, Removal of non-biodegradable organic matter from landfill leachates by adsorption. Water Res., 38 (2004) 3297–3303. T.A. Peters, Purification on landfill leachate with membrane filtration. Filtr. Sep., Jan/Feb (1998) 33–36. T.A. Peters, Purification of landfill leachate with reverse osmosis and nanofiltration. Desalination, 119 (1998) 289–293. K. Linde, A.S. Jönsson and R. Wimmerstedt, Treatment of three types of landfill leachate with reverse osmosis. Desalination, 101 (1995) 21–30. J. Wiszniowski, D. Robert, J. Surmacz-Górska, K. Miksch, S. Malato and J.V. Weber, Solar photo-
[18]
[19]
[20]
[21]
[22] [23]
[24]
[25]
23
catalytic degradation of humic acids as a model of organic compounds of landfill leachate in pilot-plant experiments: influence of inorganic salts. Appl. Catalysis B: Environ., 53 (2004) 127–137. S.K. Marttinen, R.H. Kettunen, K.M. Sormunen, R.M. Soimasuo and J.A. Rintala, Screening of physical-chemical methods for removal of organic material, nitrogen and toxicity from low strength landfill leachates. Chemosphere, 4 (2002) 851–858. M. Bodzek, J. Bohdziewicz and K. Konieczny, Membrane techniques in environmental protection, Silesian University of Technology Press, Gliwice, 1997 (in Polish). R. Rautenbach and R. Mellis, Waste water treatment by combination of bioreactor and nanofiltration, ICOM, 1993. T. Arnot and N. Zahir, A review of the potential of membrane bioreactor for waste water treatment, in: Towards Hybrid Membrane and Biotechnology Solutions for Polish Environmental Problems, Wrocław Technical University Press, Wrocław, 1995, pp. 149–161. S. Monti, ZenoGem process, in: Engineering of Membrane Processes II, Tuscany, 1994. S. Lubbecke and A. Vogelpohl, Wastewater treatment in a biological high-performance system with high biomass concentration. Water Res., 29(3) (1995) 793–802. A. Noworyta, Membrane processes in environmental protection, First Conference: Membrane and membrane processes in environmental protection, Silesian University of Technology Press, Gliwice, 1995, pp. 95–110 (in Polish). M. Pirbazari, V. Ravindran, B. Badriyha and S. Kim, Hybrid membrane filtration process for leachate treatment. Water Res., 30(11) (1996) 2691–2706.
