REMOVAL OF AMMONIACAL NITROGEN BY SIMULTANEOUS NITRIFICATION AND DENITRIFICATION IN A SINGLE AEROBICANOXIC SEQUENCING BATCH REACTORDIVYA M. BUHA, KRISHNA R. ATALIA AND NISHA K. SHAH
A single aerobic-anoxic sequencing batch reactor was fed with synthetic wastewater containing high total organic carbon to nitrogen ratios (C/N). Distinct ammonium nitrogen concentrations ranging from 50 mg/L to 800 mg/L were supplied during nine batch experiments and the reaction time ranged from about 156 h to 648 h. A consortium containing autotrophic nitrifying and heterotrophic denitrifying bacteria were investigated for aerobic nitrification and anaerobic denitrification. Aerobic, autotrophic nitrifying bacteria oxidize ammonia to nitrite and nitrate, with molecular oxygen as electron acceptor. Nitrite and nitrate are reduced to dinitrogen gas by heterotrophic denitrifying bacteria that use NOx instead of oxygen as electron acceptor. Sodium bicarbonate and sodium acetate were selected as the appropriate carbon source for cell growth and nitrogen removal. Sequences of aerated and non-aerated periods of 03 h each was repeated during each experiment conducted. Dissolved oxygen concentration (DO) was maintained at approximately 3.0 mg/L and 0.1 mg/L for aerobic and anoxic phase, respectively. pH remained maintained during each experiment due to SND (simultaneous nitrification and denitrification). Ammoniacal nitrogen removal efficiency during the study varied between 71 % and 99 %.
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