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Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Leachate recirculation between alternating aged refuse bioreactors and its effect on refuse decomposition a
b
c
c
Xiaojie Sun , Yingjie Sun , Youcai Zhao & Ya-Nan Wang a
College of Environmental Science and Engineering, Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guangxi, Guilin 541004, People's Republic of China b
School of Environment and Municipal Engineering, Qingdao Technological University, Qingdao 266033, People's Republic of China c
School of Environmental Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China Published online: 04 Nov 2013.
To cite this article: Xiaojie Sun, Yingjie Sun, Youcai Zhao & Ya-Nan Wang (2014) Leachate recirculation between alternating aged refuse bioreactors and its effect on refuse decomposition, Environmental Technology, 35:7, 799-807, DOI: 10.1080/09593330.2013.852625 To link to this article: http://dx.doi.org/10.1080/09593330.2013.852625
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. 7, 799–807, http://dx.doi.org/10.1080/09593330.2013.852625
Leachate recirculation between alternating aged refuse bioreactors and its effect on refuse decomposition Xiaojie Suna , Yingjie Sunb∗ , Youcai Zhaoc and Ya-Nan Wangc a College of Environmental Science and Engineering, Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guangxi, Guilin 541004, People’s Republic of China; b School of Environment and Municipal Engineering, Qingdao Technological University, Qingdao 266033, People’s Republic of China; c School of Environmental Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Downloaded by [Northeastern University] at 15:05 21 October 2014
(Received 12 June 2013; final version received 25 September 2013 ) In a sequencing batch bioreactor landfill system which combined a fresh and an aged refuse bioreactor, blockage occurred frequently in the aged refuse bioreactor during the treatment of leachate from the fresh refuse bioreactor. To overcome this problem, another aged refuse bioreactor was added, when blockage occurred, the two aged refuse bioreactor operated alternatively. A fresh refuse bioreactor F combined with two alternating aged refuse bioreactors A1 and A2 was called alternate recirculation process (ARP) in this study. The bioreactor system was operated in three stages, and the three bioreactors were exposed to air to facilitate surface re-aeration. The effect of the ARP on the accelerated degradation of fresh refuse was compared before and after blockage occurs in A1. The results indicated that ARP can improve the leachate production rate. The average daily net production rates of leachate in Stages 2 and 3 were approximately 2.1 and 1.6 mL (kg refuse d)−1 , respectively, which exceeded that of Stage 1 (1.3 mL (kg refuse d)−1 ). The chemical oxygen demand and NH3 –N concentrations of the leachate from Stage 1 are 1000 and 25 mg L−1 after 2.1 and 2.7 y, respectively. For Stages 2 and 3, these concentrations reach approximately after 0.877 and 1.3 y. Faster refuse settlement was observed in Stages 2 and 3, with an average daily settlement of ∼0.11%, as compared with Stage 1 (∼0.099%). ARP can accelerate the biodegradation of the fresh refuse and overcome the problem of the blockage in the aged refuse reactor. Keywords: leachate recirculation; bioreactor landfill; aged refuse bioreactor; blockage; leachate treatment
1. Introduction Sanitary landfilling is a common method for the solid waste disposal because of advantages such as its simple disposal procedure, low cost, and landscape-restoring effect on holes from mineral workings.[1,2] Landfill is designed to limit water entry, consequently reducing their environmental impact. However, such designs can hamper the process of waste degradation, which is strongly dependent on the moisture in the waste.[3] Another major drawback of this method is the production of highly contaminated leachate.[4] Leachate generated from landfills may have a long-term environmental impact if proper management is overlooked for several centuries.[5,6] By contrast, bioreactors aim to support waste degradation while providing the necessary moisture. A principal technique for leachate recirculation is the solid waste mass.[3] Leachate recirculation is an inexpensive option for leachate management because it improves the biodegradation of organic matter. Thus, the refuse can be stabilized faster, the amount of leachate is reduced, the organics and inorganics in the leachate are removed, the active
∗ Corresponding
author. Email: [email protected]
© 2013 Taylor & Francis
life of landfills is reduced, and landfill gas production is increased.[7–11] However, recent findings have indicated that traditional leachate recirculation has drawbacks. Recycled landfill leachate is often characterized by its high ammonia concentration, as compared with conventional single pass leaching.[12] Leachate recirculation during the first phase of waste decomposition leads to the accumulation of fermentation products, which primarily consist of volatile organic acids and alcohols because of the imbalance of the growth rates between fast-growing acidogenic bacteria and slow-growing methanogens.[13,14] Consequently, methanogenesis may be delayed or inhibited.[15–17] These problems are more serious in China, where the refuse is rich in food waste. To address these problems, different solutions have been proposed for changing the design of landfills and improving the leachate quality. Onay and Pohland [18] placed an air inlet at the bottom of the reactor to form vertical aerobic/anoxic/anaerobic biological zones in a simulated landfill system for the in situ attenuation of high ammonia
Downloaded by [Northeastern University] at 15:05 21 October 2014
800
X. Sun et al.
nitrogen concentrations in residual leachate. The results of He and Shen [19] indicate that intermittent aeration at the top of landfilled waste could stimulate the growth of nitrifying and denitrifying bacteria in the top and middle layers of waste. Öncü et al. [20] investigated the impact of the combined in situ intermittent aeration and leachate recirculation on the leachate quality. The changing leachate quality indicated that the changing biological activity increased the initial leachate strength. After a year of operation, the emission potential of the landfill was reduced in their study. The methods to improve leachate quality include ion exchange, air stripping, chemical precipitation, reverse osmosis, and biological treatment. Among all these options, biological treatment is most commonly used to remove ammonia from leachate because of its low cost.[21,22] Recirculating leachate between landfill cells combined with biological treatments, such as the use of an anaerobic digester or mature landfill cell, could solve this problem on at least three fronts: (1) removing acids formed in the new cells, (2) buffering landfill waste with low pH, and (3) providing inoculum to quickly establish a microbial population with the proper balance between acidogenic and methanogenic organisms.[14,23,24] Zhao et al. [25] reported that aged refuse reactors have long been used for the cost-effective treatment of landfill leachate. Moreover, the chemical oxygen demand (COD), biological oxygen demand, and ammonia–nitrogen (NH3 –N) content can be reduced, thereby making the effluent clear and odourless.[26] Xie et al. [27] constructed aged refuse bioreactors to simulate the landfill leachate degradation process. Their results show that the aged refuse bioreactor could effectively remove leachate pollutants at a hydraulic loading rate of 20 L (m3 d)−1 . However, the aged refuse bioreactor can often be blocked during operation, which could deteriorate the effluent quality. A combination of the semi-aerobic and anaerobic fresh refuse bioreactor with the aged refuse bioreactor was developed in a previous study.[28] Their results indicated that the semi-aerobic leachate recirculation process can improve the biodegradation of organic matter from fresh refuse. However, the aged refuse bioreactor is often blocked during anaerobic recirculation. The COD concentration of the leachate from A2 was 26,200 mg L−1 on day 308 because of blockage. The blockage can affect, and even disrupt, the normal operation of the system. Therefore, further research is needed. Based on the previously mentioned studies, a combined system with a fresh refuse bioreactor and two alternating Table 1.
aged refuse bioreactors (alternate recirculation process (ARP)) was developed to remove the previously observed blockage of the aged refuse reactor. The effluent from the fresh refuse bioreactor was placed in the first aged refuse bioreactor. After that, the effluent from the first aged refuse bioreactor was recirculated into the fresh refuse bioreactor. This process was performed repeatedly. When the blockage occurred or the effluent leachate quality deteriorated in the first aged refuse bioreactor, the effluent from the fresh refuse bioreactor was placed in the second aged refuse bioreactor repeatedly. The main objective of this study was to investigate the effect of the ARP on accelerating the degradation of refuse. Parameters of the leachate quality before and after the blockage of the first aged refuse bioreactor were measured and calculated. Based on the data, the effects of the blockage before and after the ARP on the degradation of refuse were compared. The attenuation mechanisms of leachate were subsequently discussed.
2. Materials and methods 2.1. Fresh refuse and aged refuse Approximately 230 kg fresh refuse was obtained daily from a residential area near Tongji University, Shanghai, China. Approximately 1200 kg fresh refuse was then transported to the laboratory in Tongji University. The refuse was weighed, bag broken, and screened by hand. The sieves used in this study had three aperture grades: 120, 40, and 8 mm. The refuse was screened into four portions with different grain sizes: >120, 40–120, 8–40, and 120 mm was not used, whereas that with a grain size of
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Leachate recirculation between alternating aged refuse bioreactors and its effect on refuse decomposition a
b
c
c
Xiaojie Sun , Yingjie Sun , Youcai Zhao & Ya-Nan Wang a
College of Environmental Science and Engineering, Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guangxi, Guilin 541004, People's Republic of China b
School of Environment and Municipal Engineering, Qingdao Technological University, Qingdao 266033, People's Republic of China c
School of Environmental Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China Published online: 04 Nov 2013.
To cite this article: Xiaojie Sun, Yingjie Sun, Youcai Zhao & Ya-Nan Wang (2014) Leachate recirculation between alternating aged refuse bioreactors and its effect on refuse decomposition, Environmental Technology, 35:7, 799-807, DOI: 10.1080/09593330.2013.852625 To link to this article: http://dx.doi.org/10.1080/09593330.2013.852625
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. 7, 799–807, http://dx.doi.org/10.1080/09593330.2013.852625
Leachate recirculation between alternating aged refuse bioreactors and its effect on refuse decomposition Xiaojie Suna , Yingjie Sunb∗ , Youcai Zhaoc and Ya-Nan Wangc a College of Environmental Science and Engineering, Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guangxi, Guilin 541004, People’s Republic of China; b School of Environment and Municipal Engineering, Qingdao Technological University, Qingdao 266033, People’s Republic of China; c School of Environmental Science and Engineering, Tongji University, Shanghai 200092, People’s Republic of China
Downloaded by [Northeastern University] at 15:05 21 October 2014
(Received 12 June 2013; final version received 25 September 2013 ) In a sequencing batch bioreactor landfill system which combined a fresh and an aged refuse bioreactor, blockage occurred frequently in the aged refuse bioreactor during the treatment of leachate from the fresh refuse bioreactor. To overcome this problem, another aged refuse bioreactor was added, when blockage occurred, the two aged refuse bioreactor operated alternatively. A fresh refuse bioreactor F combined with two alternating aged refuse bioreactors A1 and A2 was called alternate recirculation process (ARP) in this study. The bioreactor system was operated in three stages, and the three bioreactors were exposed to air to facilitate surface re-aeration. The effect of the ARP on the accelerated degradation of fresh refuse was compared before and after blockage occurs in A1. The results indicated that ARP can improve the leachate production rate. The average daily net production rates of leachate in Stages 2 and 3 were approximately 2.1 and 1.6 mL (kg refuse d)−1 , respectively, which exceeded that of Stage 1 (1.3 mL (kg refuse d)−1 ). The chemical oxygen demand and NH3 –N concentrations of the leachate from Stage 1 are 1000 and 25 mg L−1 after 2.1 and 2.7 y, respectively. For Stages 2 and 3, these concentrations reach approximately after 0.877 and 1.3 y. Faster refuse settlement was observed in Stages 2 and 3, with an average daily settlement of ∼0.11%, as compared with Stage 1 (∼0.099%). ARP can accelerate the biodegradation of the fresh refuse and overcome the problem of the blockage in the aged refuse reactor. Keywords: leachate recirculation; bioreactor landfill; aged refuse bioreactor; blockage; leachate treatment
1. Introduction Sanitary landfilling is a common method for the solid waste disposal because of advantages such as its simple disposal procedure, low cost, and landscape-restoring effect on holes from mineral workings.[1,2] Landfill is designed to limit water entry, consequently reducing their environmental impact. However, such designs can hamper the process of waste degradation, which is strongly dependent on the moisture in the waste.[3] Another major drawback of this method is the production of highly contaminated leachate.[4] Leachate generated from landfills may have a long-term environmental impact if proper management is overlooked for several centuries.[5,6] By contrast, bioreactors aim to support waste degradation while providing the necessary moisture. A principal technique for leachate recirculation is the solid waste mass.[3] Leachate recirculation is an inexpensive option for leachate management because it improves the biodegradation of organic matter. Thus, the refuse can be stabilized faster, the amount of leachate is reduced, the organics and inorganics in the leachate are removed, the active
∗ Corresponding
author. Email: [email protected]
© 2013 Taylor & Francis
life of landfills is reduced, and landfill gas production is increased.[7–11] However, recent findings have indicated that traditional leachate recirculation has drawbacks. Recycled landfill leachate is often characterized by its high ammonia concentration, as compared with conventional single pass leaching.[12] Leachate recirculation during the first phase of waste decomposition leads to the accumulation of fermentation products, which primarily consist of volatile organic acids and alcohols because of the imbalance of the growth rates between fast-growing acidogenic bacteria and slow-growing methanogens.[13,14] Consequently, methanogenesis may be delayed or inhibited.[15–17] These problems are more serious in China, where the refuse is rich in food waste. To address these problems, different solutions have been proposed for changing the design of landfills and improving the leachate quality. Onay and Pohland [18] placed an air inlet at the bottom of the reactor to form vertical aerobic/anoxic/anaerobic biological zones in a simulated landfill system for the in situ attenuation of high ammonia
Downloaded by [Northeastern University] at 15:05 21 October 2014
800
X. Sun et al.
nitrogen concentrations in residual leachate. The results of He and Shen [19] indicate that intermittent aeration at the top of landfilled waste could stimulate the growth of nitrifying and denitrifying bacteria in the top and middle layers of waste. Öncü et al. [20] investigated the impact of the combined in situ intermittent aeration and leachate recirculation on the leachate quality. The changing leachate quality indicated that the changing biological activity increased the initial leachate strength. After a year of operation, the emission potential of the landfill was reduced in their study. The methods to improve leachate quality include ion exchange, air stripping, chemical precipitation, reverse osmosis, and biological treatment. Among all these options, biological treatment is most commonly used to remove ammonia from leachate because of its low cost.[21,22] Recirculating leachate between landfill cells combined with biological treatments, such as the use of an anaerobic digester or mature landfill cell, could solve this problem on at least three fronts: (1) removing acids formed in the new cells, (2) buffering landfill waste with low pH, and (3) providing inoculum to quickly establish a microbial population with the proper balance between acidogenic and methanogenic organisms.[14,23,24] Zhao et al. [25] reported that aged refuse reactors have long been used for the cost-effective treatment of landfill leachate. Moreover, the chemical oxygen demand (COD), biological oxygen demand, and ammonia–nitrogen (NH3 –N) content can be reduced, thereby making the effluent clear and odourless.[26] Xie et al. [27] constructed aged refuse bioreactors to simulate the landfill leachate degradation process. Their results show that the aged refuse bioreactor could effectively remove leachate pollutants at a hydraulic loading rate of 20 L (m3 d)−1 . However, the aged refuse bioreactor can often be blocked during operation, which could deteriorate the effluent quality. A combination of the semi-aerobic and anaerobic fresh refuse bioreactor with the aged refuse bioreactor was developed in a previous study.[28] Their results indicated that the semi-aerobic leachate recirculation process can improve the biodegradation of organic matter from fresh refuse. However, the aged refuse bioreactor is often blocked during anaerobic recirculation. The COD concentration of the leachate from A2 was 26,200 mg L−1 on day 308 because of blockage. The blockage can affect, and even disrupt, the normal operation of the system. Therefore, further research is needed. Based on the previously mentioned studies, a combined system with a fresh refuse bioreactor and two alternating Table 1.
aged refuse bioreactors (alternate recirculation process (ARP)) was developed to remove the previously observed blockage of the aged refuse reactor. The effluent from the fresh refuse bioreactor was placed in the first aged refuse bioreactor. After that, the effluent from the first aged refuse bioreactor was recirculated into the fresh refuse bioreactor. This process was performed repeatedly. When the blockage occurred or the effluent leachate quality deteriorated in the first aged refuse bioreactor, the effluent from the fresh refuse bioreactor was placed in the second aged refuse bioreactor repeatedly. The main objective of this study was to investigate the effect of the ARP on accelerating the degradation of refuse. Parameters of the leachate quality before and after the blockage of the first aged refuse bioreactor were measured and calculated. Based on the data, the effects of the blockage before and after the ARP on the degradation of refuse were compared. The attenuation mechanisms of leachate were subsequently discussed.
2. Materials and methods 2.1. Fresh refuse and aged refuse Approximately 230 kg fresh refuse was obtained daily from a residential area near Tongji University, Shanghai, China. Approximately 1200 kg fresh refuse was then transported to the laboratory in Tongji University. The refuse was weighed, bag broken, and screened by hand. The sieves used in this study had three aperture grades: 120, 40, and 8 mm. The refuse was screened into four portions with different grain sizes: >120, 40–120, 8–40, and 120 mm was not used, whereas that with a grain size of
