Study On Treatment Of High-strength Ammonia Domestic Wastewater By Step-Feed SBR Reactors

Based on the conventional SBR, the step-feed SBR was developed by improving operation modes and its a new nitrogen removal process.The feed pattern could fully use the influent organic matter as denitrification carbon source, save aerating, decrease external carbon sources and achieve the advanced nitrogen removal.SBR reactor was employed in this experiment and the influent was simulated high-strength ammonia wastewater. Optimal distribution for influent flow was used in the step-feed SBR process and the running time was optimized by using the principle of equilibrium sludge loading. Factors which effected the removal efficiencies of COD, NH4+-N and TN such as steps of reactor, influent COD/TKN ratio, amomonia loading, etc. were discussed. In the three stage step-feed SBR, the differences of removal efficiencies of COD, NH4+-N and TN between optimal distribution and equilibrium distribution for influent flow were compared.Through experiments, the conclusions were as follows:(1) When optimal distribution for influent flow was used in the step-feed SBR process and the running time was optimized by using the principle of equilibrium sludge loading, steps of reactor had little effect on COD removal but great effect on NH4+-N and TN removal. The removal efficiencies of NH4+-N and TN were 79%～87% and 46%～70% respectively in one stage step-feed SBR,98%～99% and 81%～87% respectively in two stage step-feed SBR and 99% and 90%～94% respectively in three stage step-feed SBR.(2) When optimal distribution for influent flow was used in the step-feed SBR process and the running time was optimized by using the principle of equilibrium sludge loading, the influent COD/TKN ratio had little effect on COD and NH4+-N removal but great effect on TN removal. That is because COD/TKN ratio determines the coefficient of influent flow distribution in multi-stage influent with optimal distribution. When COD/TKN ratios were 10 (the COD and NH4+-N concentrations of the influent were 1000mg/L and 100mg/L respectively)and 5 (the COD and NH4+-N concentrations of the influent were 1000mg/L and 200mg/L respectively),the removal efficiencies of TN were 90%～94% and 57%～69% respectively. (3) As to the three stage step-feed SBR, when optimal distribution for influent flow was used in the step-feed SBR process and the running time was optimized by using the principle of equilibrium sludge loading, the TN removal efficiency can be as high as 90%～94%. However, when equilibrium distribution for influent flow was used, the TN removal efficiency was 86%～90%. The results showed that opitimal distribution for influent flow was superior to equilibrium distribution for influent flow.