Experimental Research on Biological Nitrogen Removal in a Modified SBR Treating Municipal Wastewater

A pilot-scale modified SBR process was studied to treat domestic wastewater. Experimental results show that the average NH₃-N removal ratio reached 94%, the average TN removal ratio reached 52%, the average TP removal ratio reached 80%. The effluent NH₃-N concentration was less than 1 mg/L, the effluent TN concentration was less than 20 mg/L, and the phosphorus concentration in the final effluent was below 1 mg/L and obtained on 88% of the days of operation. The ratio of influent NH₃-N/TN is equal approximately to TN removal ratio. The organic nitrogen removal is only a little. The TN removal ratio is decided by influent NH₃-N concentration mostly. The increasing anaerobic time is advantageous for nitrogen removal, but the increasing rate of TN removal would become slower after anaerobic time is more than 45 minutes. The optimal TN removal efficiency can be prejudged by the influent NH₃-N/TN ratio. Longer aerobic time is disadvantageous for nitrogen removal when the ratio of aerobic time/anaerobic time is over 0.5.