Pilot Test on Bi-cyclic Two-phase Biological Process for Nitrogen Removal from Domestic Sewage

The bi-cyclic two-phase(BICT)biological process was used to treat domestic sewage.The nitrogen removal performance of the system under different operation modes and test conditions was investigated.The test results indicate that through the adoption of a separate attached-growth reactor for nitrification,the nitrification efficiency is enhanced and the influence of SRT on nitrogen removal is diminished.Consequently,the stability of nitrogen removal is considerably improved.The operation mode and the reflux ratio of nitrified liquor are the key factors influencing the nitrogen removal efficiency.Under the suitable conditions,the removal rate of TN can reach more than 85%,and the effluent TN can be controlled at less than 15 mg/L.