Abstract: With the continuous upgrading of criteria for effluent ammonia nitrogen, it is more difficult to control ammonia nitrogen in the effluent of refinery saline wastewater treatment unit, and fluctuation often occurs during a period of time. This paper introduced the production test of adding nitrifying bacteria to achieve the standard of biological synergistic treatment. Based on the analysis of the data of the inlet and outlet water of the saline wastewater treatment system during the test, before and after the test, the paper compared the relationship between the pH of the outlet water and the nitrification system. It found out that the abnormal increase of the effluent ammonia nitrogen was mainly caused by the decrease of the alkalinity of the wastewater treatment system. It was proved that the method of adding nitrifying bacteria for biological synergism can be used as an effective emergency measure to restore the biochemical system of wastewater, establish the nitrifying system quickly and restore the ammonia nitrogen removal capacity. 

Key words: saline wastewater, ammonia nitrogen, nitrifying bacteria, biological synergism