Study On The Removal Of NH₃-N In Polishing Process Of City Sewage

In this paper, in order to remove NH₃-N to meet the standard of water for reuse (landscape) ,a series of projects about removal of NH₃-N in polishing process after second-stage of sewage plant are studied. Based on which, several sets of treatment plans on second-stage effluent of city sewage treatment farm. Such as haydite biofilter, diatomite, shrowed bacteria and based on which ,two sets of completed experiments are discussed. The result show, all of indexes of second-stage effluent treated by experimental settings can meet the standard except for NH₃-N and TP. The removal of NH₃-N by haydite is as high as 85% and when HRT is 30 min , NH₃-N content in effluent is less than 5 mg/L, but the removal of TP is not efficient to get the expected aim which is 0.2 mg/L,. when aerobic time is 2-3 hours ,the removal of NH₃-N treated by thro wed bacteria,80% of NH₃-N can be removed, not same as NH₃-N,TP cannot meet the standard. There is a good removal of TP in diatomite, and it can get 98.99% and the average is 98% or so. But the rate of NH₃-N removal is low and less than 20%,same time the NH₃-N content is over 5 mg/L. so in order to reduce the content of NH₃-N and TP enough, the completed experiments are studied.As far as the results are concerned, both haydite and throwed bacteria used as pretreatment before bio-chemical process are available for removal of NH₃-N, the optimum process can be certificated not only based on its treatment result but also other factors. In this paper ,both "haydite + diatomite"and "throwed bacteria + diatomite" are good ,under the circumstance, based on the mixed factors' advantage and disadvantage, "throwed bacteria + diatomite" is available for its easy operation and small investment. And the removal of NH₃-N and TP in this method is 80% and 97.8% respectively and can meet the expected standard in which the content of NH₃-N and TP is less 5 mg/L and 0.2 mg/L.