Laboratory Treatment Of Landfill Leachate Using An Integrated UASB-Anoxic-MBR Process

Landfill leachate refers to the wastewater generated from the municipal solid waste landfill and contains a variety of inorganic and organic chemicals. The MBR (Membrane BioReactor) technology is an advanced wastewater treatment technology using a combination of membrane filtration and activated sludge biological degradation process. In the past decade, it has gradually become a promising technology due to its unique advantages over conventional technologies in cost-effectively treating domestic wastewater and some of the industrial wastewater. However, when the MBR is applied to landfill leachate treatment. a common challenge for the membranes is their fouling problem, leading to quick drop of flow flux and then system failure. Therefore, in many cases, pre-treatment steps and processes have to be addedd before the membrane module in order to protect the membrane unit and improved the treatement effectiveness and efficiency.In this study. an integrated treatment process including hydrolysis acidification, anoxic treatment and submerged MBR with PTFE (Polytetrafluorothylene) membrane was designed to treat aged landfill leachate collected from the Asuwei Municipal Landfill in Beijing for assessing the system performance as well as the optimal conditions for operating the system.In this study, a series of experiments were designed and conducted to investigate the system performance in terms of COD removal and ammonia nitrogen removal under different levels of hydraulic retention time (HRT), sludge return ratio and aeration intensity. The results showed that the integrated system performed well in removing COD and ammonia nitrogen:the PTFE membrane did not break or damage at all during the test; when HRT=12.8h, sludge retentsion ratio=300%and aeration intensity21.8L/min, the system achieved its best performance, andthe COD removal rate can reachas high as94.96%. The results also indicate that a nonlinear relationship exists between aeration intensity and membrance fouling rate (expressed as membrance permeability rate); and an optimal balance could be achieved between membrance fouling rate and aeration energy consumption when the aeration intensity equals21.86L/min.In this study,SEM, FTIR, X-ray techniques were also used to analyze the membrane surface structure and chemical composition formed on the the membrane when the membrance fouling occurs. The SEM results show that a gel layer was formed on the membrane surface and it causes the membrane fouling problem and decreases the membrane permeability rate. The FTIR and X-ray results show that the gel layer was composed mainly of carbohydrate and protein. The membrane flux could be recovered to as much as96.08%after being cleans by physical-chemical solutions, showing its superiority in treating landfill leachate.