Modified DAT/IAT Process for Removal of Ammonia Nitrogen from Domestic Sewage

A biological contact oxidation reactor (BCOR) was set up behind demand aeration tank/intermittent aeration tank (DAT/TAT). The removal effect of ammonia nitrogen (NH₃-N) from domestic wastewater in the combined process was investigated. The results show that when the operating periods of IAT are set at two hours for aeration, one hour for sedimentation, one hour for effluent, and HRT of the BCOR is three hours, the combined process is able to remove an average of 81.1% for NH₃-N, and the average NH₃-N concentration in the effluent is 7.0 mg/L. The effluent quality meets the requirements of the Reuse of Urban Recycling Water-Water Quality Standard for Urban Miscellaneous Water Consumption (GB/T 18920- 2002). The removal efficiency of NH₃-N declines along with the increase of influent COD concentration. When the influent COD is 815.3 mg/L, the effluent NH₃-N concentration still meets the requirements of GB/T 18920-2002. However, as the influent NH₃-N concentration gradually increases, the removal efficiency of NH₃-N slightly increases at first and then obviously decreases. The influent NH₃-N concentration should be controlled at below 50 mg/L to ensure the effluent NH₃-N concentration reach the reuse standard. The appropriate pH range is 7 to 8, and the values outside this range may cause the decrease in the removal efficiency of NH₃-N.