Nitrification processes in stabilisation reservoirs

Abstract

Nitrification processes in stabilisation reservoirs have a major role in improving water quality. Wastewater effluents which enter the reservoir usually have a substantial concentration of ammonia. Oxidation of ammonia to nitrates through nitrification processes increases the options of using the water for different purposes. The largest stabilisation reservoir in Israel, Maale Kishon reservoir, is used to store secondary effluents of the Haifa treatment plant and during the summer the water flows into an operational reservoir which is used for irrigation. The operational reservoir contains large amounts of fish of different species which serve for both commercial and algal control purposes. Thus, high ammonia concentrations in the stabilisation reservoir effluents may cause fish mortality in the receiving water body and are harmful to the reclamation system. Laboratory experiments with the effluents of the stabilisation reservoir were conducted in order to find out the factors that affect nitrification processes in the reservoir and to evaluate the reasons for the inhibition of these processes. It was found that environmental factors have a decisive effect over nitrification in the stabilisation reservoir. The most important factors are the temperature, solar radiation and mixing.