Modeling ammonia-nitrogen degradation in a polluted stream with biofilm technique

The reduction of ammonia-nitrogen fluxes from polluted streams entering the Tai Lake is an important task in areas with limnetic eutrophication. Biofilm technique for the polluted streams has been proposed as one effective method to reduce ammonia-nitrogen fluxes entering the Tai Lake. In this study, ammonia-nitrogen biodegradation in a created biofilm purification engineering was evaluated by a dynamic model of ammonia-nitrogen in a polluted stream (Linzhuanggang) in western Tai Lake of China. The ammonia-nitrogen biodegradation model was described with Monod dynamic equation and hydraulic characteristic of the stream, and modified and evaluated by analyzing biodegradation effect in different periods and at different environmental conditions. Due to temperature dependence and seasonal variation in the stream, decrease in ammonia-nitrogen concentration mainly occurred during summer periods, which affected biodegradation effect of ammonia-nitrogen to some degree. The model showed that the purification engineering reduced the nitrogen transport to the Tai Lake with approximately 5%~40% in the test period.