[Study on long-term stability of biological nitrogen removal via nitrite from real landfill leachate]

The long-term stability of nitrogen removal from municipal landfill with high ammonia nitrogen (NH(4+)-N) content was investigated by using a biological system consisting of a first-stage up-flow anaerobic sludge bed (UASB) and sequencing batch reactor (SBR) under normal and low temperature conditions. The 623 days experimental results clearly showed: the efficient denitrification and methanogenesis were conducted in a same UASB reactor, and almost 100% of denitrification was obtained, when feed COD concentration ranged from 1,000 mg x L(-1) to 13 800 mg x L(-1), effluent COD concentration was between 150 mg x L(-1) and 1,234 mg x L(-1), and when the influent ammonia nitrogen (NH(4+)-N) changed from 574 mg x L(-1) to 2,360 mg-L(-1), the effluent NH:-N was below 10 mg x L(-1), the removal efficiency reached 90% and 98%, respectively. Especially, above 99.2% removal efficiency of TN was obtained, and effluent TN concentration was below 30 mg L(-1)), advanced and efficient nitrogen and organic removal were achieved in the biological system. Furthermore, stable nitrification and denitrification were achieved during the entire experiment period, especially, were maintained successfully for 171 days at the temperature below 15 degrees C and the lowest temperature of 10. 2 degrees C during two winters.