Study On Aerobic Denitrification In Activated Sludge System

Nitrogen contamination which is responsible for eutrophication has been a serious environmental problem gradually noticed by the whole world. Nitrogen removal from water is the emphasis and one of the points of issues in the studies of water pollution treatment. Biological nitrogen removal is considered as the best method. According to the traditional nitrogen removal theory, biological nitrogen removal is made up of nitrification and denitrification. Nitrification is proceeding under aerobic condition, denitrification is under anoxic/anaerobic condition instead. But in recent years, people had found denitrification under aerobic condition and called the phenomena as aerobic denitrification.At present, the investigations on aerobic denitrification focus on aerobic denitrifiers while ignoring its impression in activated sludge system, accompanied with nitrification while not making clear between nitrification nitrogen removal and aerobic denitrification, neglect the products of the process. Directing to these problems, laboratory-scale experiments were conducted in Sequencing Batch Reactor(SBR). In the study, NO₃^--N and NO₂^--N were put into two reactors respectively. Two sets of aerobic denitrification activated sludge system were acclimated at high DO. The nitrogen removal from assimilatory and dissimilatory pathways, the influence factors such as COD/N, N load, DO, the poisonous products NO, N₂O were studied deeply.The results show aerobic denitrification can be achieved both in the two activated sludge systems. NO₃^--N and NO₂^--N can be transformed into gases and removed from water. The traditional denitrification due to the variation of DO concentration in macroscopical or microcosmic environment is excluded. The lost nitrogen from assimilatory pathway accounts for 35% and 38% in two systems respectively.The lower influence COD/N, the lower aerobic denitrification effect of the two...