Heterotrophic Nitrification and Aerobic Denitrification of a Wastewater from a Chemical Company by Alcaligenes faecalis No.4

A wastewater from a chemical company (abbreviated as WC) containing approximately 5000 mg NH4 -N/L ammonium and a slight amount of BOD was treated with Alcaligenes faecalis No.4 (No.4),which is capable of heterotrophic nitrification and aerobic denitrification. The repeatedbatch operation was conducted at 30°C for 900 h at controlled dissolved oxygen concentration (DO) of 2-3 mg/L in the presence of citrate as the carbon source and inorganic nutrients. The removal efficiency of ammonium reached 90-100% within 24-30 h, and the average ammonium removal rate was 1.1 kg NH4 -N/m3 /day, which is more than 100 fold greater than that achieved with conventional nitrification-denitrification processes. The operation was shut-down for 220 h, and after that the ammonium removal activity achieved by No.4 resumed without delay, and a high removal rate was maintained. The addition of 3% NaCl to the wastewater resulted in almost the same ammonium removal rate as that without NaCl.