Conversion of ammonia to dinitrogen in wastewater by Nitrosomonas europaea

Because Nitrosomonas europaea contains ammonia-oxidizing enzyme, nitrite re ductase, and nitrous oxide reductase, the conversion of ammonia to dinitrog en was tried with different reaction conditions. In aerobic reaction condit ions, ammonium was converted to nitrite (NO2-), while under oxygen-limiting or oxygen-free conditions, NO2-N formed from ammonia oxidation by N. europ aea was reduced to N2O and dinitrogen with 22% conversion. During denitrifi cation, optimal pH for the production of N2O and dinitrogen was found to be 7.0-8.0. Dinitrogen was not produced in acidic pH <7.0. A low partial oxyg en pressure as well as oxygen-free conditions are favorable for high produc tion of dinitrogen.