Aerobic and anaerobic biodegradation of polyacrylamide as the sole carbon source
Wenzhe SONG1,2,, Yu ZHANG1,2,,, Min YANG1,2 1.State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 2.University of Chinese Academy of Sciences, Beijing 100049, China
Abstract:Polymer flooding was used to enhance the oil recovery in the oilfield, and the partial hydrolyzed anionic high molecular weight polyacrylamide (PAM) would remained in the produced wastewater. It was found the cleavage of the main carbon backbone and biodegradability of PAM will occur under aerobic and anaerobic conditions using the PAM and coexisting starch as the carbon sources, while the biodegradability of PAM is uncertainty when it was used as the sole carbon source. Aerobic suspended sludge reactor (ASSR) and upflow anaerobic sludge blanket (UASB) were used to treat the synthetic wastewater containing PAM as the sole carbon source (hydraulic residence time (HRT) 2 d, PAM concentration 200 mg·L-1), respectively. The results indicated that PAM concentration and viscosity of ASSR effluent did not decrease, after 84 d running, the biomass was washed out and ASSR system collapsed. However, PAM concentration and the viscosity of UASB effluent decreased to 169.81 mg·L-1 and 1.50 mPa·s, respectively. Through the analysis of the flow field fractionation coupled with multi-angles laser lights method, the molecular weight of PAM decreased from 2.17×107 Da to 3.35×106 Da by. This indicated that the anaerobic biodegradation of PAM could occur when it was used as the sole carbon source, as well as the disruption of its main carbon backbone. Extending the HRT from 2 d to 8 d could improve the anaerobic biodegradation of PAM as the sole carbon source, and PAM molecular weight in UASB effluent further declined to 1.60×106 Da. At the same time, the viscosity of UASB effluent decreased from 1.50 mPa·s to 1.21 mPa·s. The tanks-in-series biofilm reactors could also improve the anaerobic biodegradation of PAM as the sole carbon source, and PAM molecular weight and the viscosity of reactor effluent were 1.87×106 Da and 1.26 mPa·s at the HRT of 4 d, respectively. Key words:polyacrylamide/ produced wastewater/ sole carbon sources/ extension of the hydraulic residence time.
图4场流光散射分析进出水聚丙烯酰胺保留时间 Figure4.Retention time of inlet and effluent PAM with the analysis of flow field fractionation coupled with multi-angles laser light
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1.State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 2.University of Chinese Academy of Sciences, Beijing 100049, China Received Date: 2019-01-04 Accepted Date: 2019-03-25 Available Online: 2019-09-30 Keywords:polyacrylamide/ produced wastewater/ sole carbon sources/ extension of the hydraulic residence time Abstract:Polymer flooding was used to enhance the oil recovery in the oilfield, and the partial hydrolyzed anionic high molecular weight polyacrylamide (PAM) would remained in the produced wastewater. It was found the cleavage of the main carbon backbone and biodegradability of PAM will occur under aerobic and anaerobic conditions using the PAM and coexisting starch as the carbon sources, while the biodegradability of PAM is uncertainty when it was used as the sole carbon source. Aerobic suspended sludge reactor (ASSR) and upflow anaerobic sludge blanket (UASB) were used to treat the synthetic wastewater containing PAM as the sole carbon source (hydraulic residence time (HRT) 2 d, PAM concentration 200 mg·L-1), respectively. The results indicated that PAM concentration and viscosity of ASSR effluent did not decrease, after 84 d running, the biomass was washed out and ASSR system collapsed. However, PAM concentration and the viscosity of UASB effluent decreased to 169.81 mg·L-1 and 1.50 mPa·s, respectively. Through the analysis of the flow field fractionation coupled with multi-angles laser lights method, the molecular weight of PAM decreased from 2.17×107 Da to 3.35×106 Da by. This indicated that the anaerobic biodegradation of PAM could occur when it was used as the sole carbon source, as well as the disruption of its main carbon backbone. Extending the HRT from 2 d to 8 d could improve the anaerobic biodegradation of PAM as the sole carbon source, and PAM molecular weight in UASB effluent further declined to 1.60×106 Da. At the same time, the viscosity of UASB effluent decreased from 1.50 mPa·s to 1.21 mPa·s. The tanks-in-series biofilm reactors could also improve the anaerobic biodegradation of PAM as the sole carbon source, and PAM molecular weight and the viscosity of reactor effluent were 1.87×106 Da and 1.26 mPa·s at the HRT of 4 d, respectively.
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