As an important part of sewage treatment, urban sewage treatment plant is the key to water pollution control. However, the problem of high concentration of ammonia nitrogen wastewater in sewage treatment plant has always existed. The reasons for high ammonia nitrogen in effluent of this paper are as follows:
1. Nitrifying bacteria decreased in activity and oxygen transport concentration gradient;
2. Due to the process itself, the residence time of aeration tank unit is relatively small, and the impact load resistance of the system is relatively weak.
Sewage treatment plant solutions:
(1) reduce the inflow, reduce the internal reflux ratio, extend the actual hydraulic residence time of the aerobic unit, improve the nitrification effect, and pay close attention to the changes of other water quality indexes and sludge indexes;
(2) try to avoid sludge disintegration or sludge expansion;
In case of such situation, it is necessary to add coagulant or iron salt to the system quickly to improve the flocculation and sedimentation of sludge.