Biological Nitrogen Removal From Landfill Leachate By Shortcut Nitrification-denitrification

In recent years, nitrogen removal from high-strength ammonium and low C/N ratio wastewater is still a focus and difficult problem in wastewater treatment. In this research paper, the treatment for landfill leachate of erfeishan refuse landfill in WuHan was studied in a completely mixed bioreactor. As a result, denitrification via nitrite is a dominant nitrogen removal process in treatment of landfill leachate.It was found that, the ammonium removal rate of landfill leachate was 85% by the activated sludge acclimated when the initial ammonium concentration was 30～90mg/L, the most of the ammonium was removal by shortcut nitrification and the else was removal by stripping of the aeration and assimilation of the microorganisms. Experimental results showed that, in this process, the optimal pH of the shortcut nitrification was 8.0～8.5; when the pH was less than 6,the nitrification is completely inhibited; when the pH was 6～7, at the end of aeration, the Nitrobacteria become the dominant bacteria because of the dropping of the free ammonia(FA) concentration. It is known to all, the activity of the Nitrobacteria and Nitrosomonas was affected by FA concentration, so nitrification was affected by FA concentration. According to the author's research results, the FA concentration which inhibit the Nitrobacteria was below 1.0mg/L,which inhibit the Nitrosomonas was above 10mg/L.The temperature not only affect the physiological activation of microorganisms but also affect the FA concentration. In this research, the optimum temperature of the shortcut nitrification is 25℃～30℃,during the 25℃～30℃, the accumulated fraction of the nitrite was above 90%.With the difference from other most research results, in this research, the dissolved oxygen (DO) (0～2.5mg/L)almost can't affect the shortcut nitrification.At the end of this paper, the factors which influence the shortcut denitrification was discussed. By detecting the nitrite and nitrate in effluent after aeration, it was found that the denitrification rate in this reactor was about 85%. This phenomenon indicated that shortcut denitrification didn't need strict control to the conditions, if the shortcut nitrification can take place successfully, the shortcut denitrification can take place successfully too.