Study On Nitrogen Removal Behavior In Landfill Leachate Treatment Using Anoxic Bio-Filter And Aerobic Membrane Bioreactor Processes

Landfill leachate discharged from landfill has severely caused secondary pollution to the surface water, groundwater and soil, which can directly threat to human health. Due to the ammonia with high concentration presented in landfill leachate, it is quite difficult to achieve the desirable removal efficiency of ammonia and organic compounds successfully in biological leachate treatment processes. Therefore, how to develop an alternative technique to effectively improve the biological denitrification of leachate treatment efficiency to meet with the wastewater discharge stander has become a target in environmental protection work.In this work, the nitrogen removal behaviors in landfill leachate treatment were investigated at various of C/N, dilution ratios and recycle ratios by using an anoxic bio-filter and aerobic membrane bioreactor processes. In addition, the fouling behaviors and cleaning methods of membrane were investigated. The results were summarized as follows:(1) When dilution ratio of landfill leachate was set at 10, the activities of both denitrificant and nitrifying bacteria in anoxic bio-filter and aerobic MBR were not affected by C/N, and the average removal efficiency of NH₄⁺-N and TN possibly reached at about 90%and 65%, respectively; When dilution ratio dropped to 5, the de-nitrification activity could be enhanced effectively and nitrite accumulation could be eliminated by adding the external carbon of glucose to increase the C/N, and NH₄⁺-N and TN in whole system could be maintained at the range of 69%～78% and 46%～50%, respectively.(2) When dilution ratio decreased from 20 to 10, since the relatively high NH₄⁺-N loading could increase nitrafication reaction rate, the removal efficiency of NH₄⁺-N and TN increased. However, when dilution ratio dropped to 5, the removal efficiency of NH₄⁺-N and TN decreased due to the significant accumulation of nitrite in effluent. This finding indicated that nitrite oxidizing bacteria appeared to be inhibited more easily than ammonia oxidizing bacteria at the relatively higher NH₄⁺-N concentration level in the aerobic vessel.(3) When the recycle ratio of the aerobic vessel to anoxic column was raised from 100% to 200%, the average removal efficiency of both NH₄⁺-N and TN in whole system did not change, which could maintain at about 90% and 70%, respectively.(4) The compact gelatinous layer forming at the surface of membrane was mainly attributable to membrane fouling occurred at membrane module during the operation. Within the chemical cleaning method, it was observed that the acidic cleaning could not wash off the fouling, whereas the initially alkaline and followed acidic cleaning could remove the fouling more effectively.