FACTORS INHIBITING NITRIFICATION OF AMMONIA IN DEEP WASTE-WATER RESERVOIRS

Nitrification of ammonia in wastewater reservoirs is very slow, in spite of the ubiquitous presence of nitrifying bacteria. In an attempt to identify the reasons, the effect of several factors on the rate of nitrification and viability of N. europaea was studied. Light, NH2OH and NH2NH2 were found to be inhibitory to exponentially growing cells of Nitrosomonas europaea, while ammonia provided limited protection. Stationary phase cells were unaffected by light. Water samples from two wastewater reservoirs had a variable effect upon viability and nitrification of laboratory cultures of N. europaea upon illumination, while long-term incubation of N. europaea cells placed in semi-permeable containers at different depths in the reservoirs had generally no effect on their viability.