Gas analysis reveals novel aerobic deammonification in thermophilic aerobic digestion

A laboratory-scale thermophilic aerobic digester was operated with piggery wastewater. The operating temperature varied from 50-70°C. It has been found that excessive nitrogen removal occurred in the laboratory-scale thermophilic system at various HRTs. Nitrite and nitrate were not observed in the effluent. Gas measurement reveals the presence of significant amount of N₂O along with NH₃ gas. The rational production of N₂O gas in accordance with temperature and HRT suggests that biologically mediated deammonification processes significantly contribute to the N removal. Although further microbiological investigation is required to clarify the exact nitrogen removal mechanism, the large production of N₂O gas seems to be a result of the existence of a rapid growing heterotrophic deammonification process in the thermophilic system.