Study On UASB-A/O-MBR Treating Landfill Leachate Wastewater

Landfill leachate is a kind of wastewater containing high concentration of ammonia nitrogen and difficult to degrade organic matter and is very complex.It is difficult to deal with the conventional treatment methods.In this study,the landfill leachate has been treated by a series of anaerobic-aerobic biological treatment technology,including Upflow Anaerobic Sludge Blanket(UASB)and anoxic-aerobic membrane bioreactor(A/O-MBR).The performances of biological treatments on removal of COD,NH4+-N,NO3--N,and TN have been studied.The UASB showed a remarkable performance of COD removal,and the effluent COD concentration and removal rate were stabilized at 2500 mg/L and up to 90%,respectively.The removal rates of NH4+-N,and TN were both around 5%,which need to be followed by a nitrification-denitrification biological treatment.The volume load of COD and gas rate were stabilized at 9.7 kgCOD/(m3·d)and 4.3 L/h,respectively,which showed significantly positive correlation.UASB effluent colority changed from dark brown to pale green,indicating that microbial decolorization of leachate in the UASB also had a good performance.Aeration could blow off a large number of acidic gases from leachate,which lead to a rise of pH.A part of Ni4+-N in the landfill leachate was blown off due to high Ni4+-N concentration and higher pH.The A/O-MBR process showed a good performance on the treatment of UASB effluent.The COD,NH4+-N concentration in membrane effluent were 85.22 mg/L and 23.03 mg/L,and the average removal rate were 96.08%and 98.32%,respectively.COD and NH4+-N have reached the requirements of the landfill pollution control standard(GB16889-2008).During the experiment process,PVDF membrane has been cleaned four times.The appearances of vorticella and rotifer indicated the better nitrification and system stability of MBR process.