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Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Reverse osmosis and nanofiltration of biologically treated leachate a
a
a
a
b
Aare Kuusik , Karin Pachel , Argo Kuusik , Enn Loigu & Walter Z. Tang a
Department of Environmental Engineering, Tallinn University of Technology, Tallinn 19086, Estonia b
Department of Civil and Environmental Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174, USA Published online: 15 May 2014.
To cite this article: Aare Kuusik, Karin Pachel, Argo Kuusik, Enn Loigu & Walter Z. Tang (2014) Reverse osmosis and nanofiltration of biologically treated leachate, Environmental Technology, 35:19, 2416-2426, DOI: 10.1080/09593330.2014.908241 To link to this article: http://dx.doi.org/10.1080/09593330.2014.908241
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 19, 2416–2426, http://dx.doi.org/10.1080/09593330.2014.908241
Reverse osmosis and nanofiltration of biologically treated leachate Aare Kuusika , Karin Pachela , Argo Kuusika , Enn Loigua and Walter Z. Tangb∗ a Department
of Environmental Engineering, Tallinn University of Technology, Tallinn 19086, Estonia; b Department of Civil and Environmental Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174, USA
Downloaded by [University of Winnipeg] at 07:00 28 August 2014
(Received 25 October 2013; final version received 20 March 2014 ) Experiments of nano-filtration (NF) and reverse osmosis (RO) were conducted to remove most pollutants from the biological treated leachate. For example, the purified permeate after reverse osmosis treatment with spiral membranes reached effluent water quality as follows: COD of 57 mg O2 /l, BOD7 of 35 mg O2 /l, and suspended solid of 1 mg/l which satisfies the discharge standards in Estonia. For both RO and NF, conductivity can be reduced by 91% from 6.06 to 0.371 mS/cm by RO and 99% from 200 to 1 mS/cm by NF. To test the service life of the RO spiral membranes, the process was able to reduce chemical oxygen demand (COD) and biological oxygen demand (BOD) of biologically treated leachate by 97.9% and 93.2% even after 328 and 586 hours, respectively. However, only 39.0% and 21.7% reductions of Ptot and Ntot were achieved. As a result, neither RO (spiral membranes process) nor NF was able to reduce the total nitrogen (TN) to the required discharge limit of 15 mg/l. Keywords: landfill leachate; leachate characteristics; pre-treatment; biological treatment; reverse osmosis; nanofiltration
1. Introduction More than 500 thousand tons of municipal solid waste are being disposed annually at five landfills in Estonia. Effective management of landfill leachate is one of the major challenges to meet strict European Union discharge standards at these landfills.[1] For example, leachate treated by activated sludge (AS) from the Väätsa landfill is directly discharged into a small river. Due to the small flow rate, the discharged leachate could impose significant impact on the water quality due to insufficient dilution if the discharge standards were not met.[2] The quantity of leachate depends not only on the characteristics of climatic and meteorological conditions of the site, but also on the physical characteristics of waste. The flow rate of landfill leachate in Väätsa site is directly related to the intensity of rainfall and melting of snow. Diurnal, weekly and annual flow rates of landfill leachate have large variations. For example, the leachate flow rate in Väätsa landfill ranged from 2 to 130 m3 /day in the past. Annual mean flow rate was in the range from 10 to 20 m3 /day. Calculated specific leachate runoff was 8 l/s/ha. The leachate flow rate from Väätsa landfill was 5500 m3 /yr in the rainy year of 2008 and only 2000 m3 /yr in the draught year of 2006. Since the leachate flow rate changes significantly, mean leachate quality, as given in Table 1, shows a low BOD7 /COD ratio of 0.38 and high ammonia concentration of 198 mg/l. After six years of successful operation from 2002 to 2008, AS treatment process was not working at its design ∗ Corresponding
author. Email: tangz@fiu.edu
© 2014 Taylor & Francis
conditions. As the landfill ages, more and more nonbiodegradable organic compounds, such as humic and fulvic acids, are produced.[3] In addition, ammonia concentration increased significantly from 50 to 164 mg/l. As a result, ammonia–nitrogen concentration could not be reduced to the discharge standard of 15 mg/l without additional treatment. Ammonia toxicity to microorganisms in the AS tank also made the sedimentation tank not working as it was designed. Consequently, the effluent was dark and contained high concentration solids. Since AS was not primarily designed to remove non-biodegradable organic chemicals, removal of non-biodegradable after AS is critical to meet the discharge standards especially after the BOD7 /COD ratio dropped to less than 0.18 in 2011, which prompted this study by using reverse osmosis (RO) and nanofiltration (NF) to improve the discharge quality. In the literature, Mohammad et al. [4] investigated NF of leachate. Turan et al. [5] compared RO and NF performance in treating diary wastewater. To meet the Estonia discharge standards, membrane technologies, such as RO, can be used either as a main step in a landfill leachate treatment chain or as single posttreatment step. Membranes such as RO and NF have pore sizes that are sufficient to retain non-biodegradable organic pollutants and are very effective in the physical separation of a variety of large non-biodegradable compounds from water.[6] Mohammad et al. [4] reported that NF removed more than 85% total suspended solids, heavy metals,
Environmental Technology
Downloaded by [University of Winnipeg] at 07:00 28 August 2014
Table 1.
Leachate water quality.
Parameter
Unit
Concentration
BOD7 COD TN NH4 TP Conductivity SO4 Cl−
mg O2 /l mg O/l mg N/l mg N/l mg P/l μS/cm mg/l mg/l
529 1366 298 198 4.6 8090 588 439
2.2. Experimental set-up of RO and NF The flow diagram for the experimental set-up of RO and NF is shown in Figure 2. The Ultra-FLO pilot plant of lowpressure reverse osmosis (LRO) was purchased from the Ultra-FLO Pte Ltd. in Singapore. The system consists of two LRO membrane (4040 – spiral membranes) cartridges and one BT420 UF cartridge, one 5 μm guard-filter, one feed pump, as well as control valves, pressure gauges and flow meters. The system was connected with either Polyvinyl Chloride or stainless steel pipes. According to the manufacturer’s recommendation, the flow rates for RO were kept at the following ranges: permeate at 0.2 m3 /h, concentrate at 0.3 m3 /h, while the feedback flow rate was kept from 0.9 to 1.2 m3 /h. When NF-filter was tested, the flow rate through the NF filter is about 0.3 m3 /h, while the feedback flow rate was operated from 0.9 to 1.2 m3 /h. Figure 3 shows the photos of experimental set-up from both the front and side views. The front two cartridges are pre-treated to remove suspended particles. The RO or NF membranes can be seen from the side view of the two stainless steel columns.
conductivity and Chemical Oxygen Demand (COD). However, only 45.4% and 20.5% removal was achieved for nitrate and ammonia–nitrogen, respectively. Therefore, the objectives of this study are to assess the treatment efficiencies of RO and NF of the biologically treated leachate so that the effluent qualities can meet the Estonia discharge standards. In addition, after treatment efficiencies by both RO and NF were compared, the best membrane for fullscale implementation was selected. This study reports the treatment efficiencies of the biologically treated leachate at the Väätsa landfill by pilot-scale RO and NF.
2.
2.3. Experimental procedure The Ultra-FLO pilot plant was operated in either RO or NF mode to test the treatment efficiency of either RO or NF. NF testing spiral filtration uses NE 4040-90 membrane. The permeate expense ratio (P/F) was kept at 1.7. Biologically treated landfill leachate passed through a cloth filter and two microfilter cartridges BB 5 mm. Finally, it passed through either RO membrane or NF spiral wound NE 4040-90 membrane. During the exhaustion test, two successive 5 mm microfilter BB Cartridge Filters, or two new filters of spiral wound PP 5 μm, and two consecutive PO spiral wound NF 24040 or NF spiral wound NE 4040-90 were used to test the lifetime of these membranes in treating the biologically
Experimental design
2.1. Biological leachate treatment systems The biological treatment systems as shown in Figure 1 include a biological lagoon and an AS which were built in 2002. Väätsa biological treatment process of leachate has two components. One is biological lagoon which has been further divided into two processes, aerobic vs. anoxic and the other is AS. All the data were taken after either biological lagoon or AS treatment of the effluent from biological lagoon.
Inlet leachate 30 m3/d BOD 7 =3000 mg/l COD= 4000 mg/l
Excess sludge
Phosphoric acid 1,6 l/d Lamella separator Oxidation tank Return sludge
Effluent for diluting 40 m3/d
Figure 1.
2417
Väätsa landfill biological treatment process.
70 m3/d
Excess sludge
Lagoon
Oxidation part
Excess sludge tank
Outlet effluent 30 m3/d BOD 7
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Reverse osmosis and nanofiltration of biologically treated leachate a
a
a
a
b
Aare Kuusik , Karin Pachel , Argo Kuusik , Enn Loigu & Walter Z. Tang a
Department of Environmental Engineering, Tallinn University of Technology, Tallinn 19086, Estonia b
Department of Civil and Environmental Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174, USA Published online: 15 May 2014.
To cite this article: Aare Kuusik, Karin Pachel, Argo Kuusik, Enn Loigu & Walter Z. Tang (2014) Reverse osmosis and nanofiltration of biologically treated leachate, Environmental Technology, 35:19, 2416-2426, DOI: 10.1080/09593330.2014.908241 To link to this article: http://dx.doi.org/10.1080/09593330.2014.908241
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 19, 2416–2426, http://dx.doi.org/10.1080/09593330.2014.908241
Reverse osmosis and nanofiltration of biologically treated leachate Aare Kuusika , Karin Pachela , Argo Kuusika , Enn Loigua and Walter Z. Tangb∗ a Department
of Environmental Engineering, Tallinn University of Technology, Tallinn 19086, Estonia; b Department of Civil and Environmental Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174, USA
Downloaded by [University of Winnipeg] at 07:00 28 August 2014
(Received 25 October 2013; final version received 20 March 2014 ) Experiments of nano-filtration (NF) and reverse osmosis (RO) were conducted to remove most pollutants from the biological treated leachate. For example, the purified permeate after reverse osmosis treatment with spiral membranes reached effluent water quality as follows: COD of 57 mg O2 /l, BOD7 of 35 mg O2 /l, and suspended solid of 1 mg/l which satisfies the discharge standards in Estonia. For both RO and NF, conductivity can be reduced by 91% from 6.06 to 0.371 mS/cm by RO and 99% from 200 to 1 mS/cm by NF. To test the service life of the RO spiral membranes, the process was able to reduce chemical oxygen demand (COD) and biological oxygen demand (BOD) of biologically treated leachate by 97.9% and 93.2% even after 328 and 586 hours, respectively. However, only 39.0% and 21.7% reductions of Ptot and Ntot were achieved. As a result, neither RO (spiral membranes process) nor NF was able to reduce the total nitrogen (TN) to the required discharge limit of 15 mg/l. Keywords: landfill leachate; leachate characteristics; pre-treatment; biological treatment; reverse osmosis; nanofiltration
1. Introduction More than 500 thousand tons of municipal solid waste are being disposed annually at five landfills in Estonia. Effective management of landfill leachate is one of the major challenges to meet strict European Union discharge standards at these landfills.[1] For example, leachate treated by activated sludge (AS) from the Väätsa landfill is directly discharged into a small river. Due to the small flow rate, the discharged leachate could impose significant impact on the water quality due to insufficient dilution if the discharge standards were not met.[2] The quantity of leachate depends not only on the characteristics of climatic and meteorological conditions of the site, but also on the physical characteristics of waste. The flow rate of landfill leachate in Väätsa site is directly related to the intensity of rainfall and melting of snow. Diurnal, weekly and annual flow rates of landfill leachate have large variations. For example, the leachate flow rate in Väätsa landfill ranged from 2 to 130 m3 /day in the past. Annual mean flow rate was in the range from 10 to 20 m3 /day. Calculated specific leachate runoff was 8 l/s/ha. The leachate flow rate from Väätsa landfill was 5500 m3 /yr in the rainy year of 2008 and only 2000 m3 /yr in the draught year of 2006. Since the leachate flow rate changes significantly, mean leachate quality, as given in Table 1, shows a low BOD7 /COD ratio of 0.38 and high ammonia concentration of 198 mg/l. After six years of successful operation from 2002 to 2008, AS treatment process was not working at its design ∗ Corresponding
author. Email: tangz@fiu.edu
© 2014 Taylor & Francis
conditions. As the landfill ages, more and more nonbiodegradable organic compounds, such as humic and fulvic acids, are produced.[3] In addition, ammonia concentration increased significantly from 50 to 164 mg/l. As a result, ammonia–nitrogen concentration could not be reduced to the discharge standard of 15 mg/l without additional treatment. Ammonia toxicity to microorganisms in the AS tank also made the sedimentation tank not working as it was designed. Consequently, the effluent was dark and contained high concentration solids. Since AS was not primarily designed to remove non-biodegradable organic chemicals, removal of non-biodegradable after AS is critical to meet the discharge standards especially after the BOD7 /COD ratio dropped to less than 0.18 in 2011, which prompted this study by using reverse osmosis (RO) and nanofiltration (NF) to improve the discharge quality. In the literature, Mohammad et al. [4] investigated NF of leachate. Turan et al. [5] compared RO and NF performance in treating diary wastewater. To meet the Estonia discharge standards, membrane technologies, such as RO, can be used either as a main step in a landfill leachate treatment chain or as single posttreatment step. Membranes such as RO and NF have pore sizes that are sufficient to retain non-biodegradable organic pollutants and are very effective in the physical separation of a variety of large non-biodegradable compounds from water.[6] Mohammad et al. [4] reported that NF removed more than 85% total suspended solids, heavy metals,
Environmental Technology
Downloaded by [University of Winnipeg] at 07:00 28 August 2014
Table 1.
Leachate water quality.
Parameter
Unit
Concentration
BOD7 COD TN NH4 TP Conductivity SO4 Cl−
mg O2 /l mg O/l mg N/l mg N/l mg P/l μS/cm mg/l mg/l
529 1366 298 198 4.6 8090 588 439
2.2. Experimental set-up of RO and NF The flow diagram for the experimental set-up of RO and NF is shown in Figure 2. The Ultra-FLO pilot plant of lowpressure reverse osmosis (LRO) was purchased from the Ultra-FLO Pte Ltd. in Singapore. The system consists of two LRO membrane (4040 – spiral membranes) cartridges and one BT420 UF cartridge, one 5 μm guard-filter, one feed pump, as well as control valves, pressure gauges and flow meters. The system was connected with either Polyvinyl Chloride or stainless steel pipes. According to the manufacturer’s recommendation, the flow rates for RO were kept at the following ranges: permeate at 0.2 m3 /h, concentrate at 0.3 m3 /h, while the feedback flow rate was kept from 0.9 to 1.2 m3 /h. When NF-filter was tested, the flow rate through the NF filter is about 0.3 m3 /h, while the feedback flow rate was operated from 0.9 to 1.2 m3 /h. Figure 3 shows the photos of experimental set-up from both the front and side views. The front two cartridges are pre-treated to remove suspended particles. The RO or NF membranes can be seen from the side view of the two stainless steel columns.
conductivity and Chemical Oxygen Demand (COD). However, only 45.4% and 20.5% removal was achieved for nitrate and ammonia–nitrogen, respectively. Therefore, the objectives of this study are to assess the treatment efficiencies of RO and NF of the biologically treated leachate so that the effluent qualities can meet the Estonia discharge standards. In addition, after treatment efficiencies by both RO and NF were compared, the best membrane for fullscale implementation was selected. This study reports the treatment efficiencies of the biologically treated leachate at the Väätsa landfill by pilot-scale RO and NF.
2.
2.3. Experimental procedure The Ultra-FLO pilot plant was operated in either RO or NF mode to test the treatment efficiency of either RO or NF. NF testing spiral filtration uses NE 4040-90 membrane. The permeate expense ratio (P/F) was kept at 1.7. Biologically treated landfill leachate passed through a cloth filter and two microfilter cartridges BB 5 mm. Finally, it passed through either RO membrane or NF spiral wound NE 4040-90 membrane. During the exhaustion test, two successive 5 mm microfilter BB Cartridge Filters, or two new filters of spiral wound PP 5 μm, and two consecutive PO spiral wound NF 24040 or NF spiral wound NE 4040-90 were used to test the lifetime of these membranes in treating the biologically
Experimental design
2.1. Biological leachate treatment systems The biological treatment systems as shown in Figure 1 include a biological lagoon and an AS which were built in 2002. Väätsa biological treatment process of leachate has two components. One is biological lagoon which has been further divided into two processes, aerobic vs. anoxic and the other is AS. All the data were taken after either biological lagoon or AS treatment of the effluent from biological lagoon.
Inlet leachate 30 m3/d BOD 7 =3000 mg/l COD= 4000 mg/l
Excess sludge
Phosphoric acid 1,6 l/d Lamella separator Oxidation tank Return sludge
Effluent for diluting 40 m3/d
Figure 1.
2417
Väätsa landfill biological treatment process.
70 m3/d
Excess sludge
Lagoon
Oxidation part
Excess sludge tank
Outlet effluent 30 m3/d BOD 7
