Characterization of Alcaligenes aquatilis as a novel member of heterotrophic nitrifier-aerobic denitrifier and its performance in treating piggery wastewater

• Heterotrophic nitrification-aerobic denitrification in A. aquatilis was discovered. • A. aquatilis AS1 could grow and remove ammonia under broad environmental conditions. • AS1 could efficiently remove NH 4 + -N in high-ammonia piggery wastewater (2000 mg/L). • A maximum NH 4 + -N removal rate of 30.5 mg/L/h and 569.67 mg/L/d by AS1 was observed. A novel strain AS1 with heterotrophic nitrifying-aerobic denitrifying capacity in the species of Alcaligenes aquatilis was isolated from the aerobic activated sludge. It showed a great capability of ammonia removal, and the aerobic metabolic pathways to yield gaseous-nitrogen by hydroxylamine oxidation and nitrite denitrification were proposed. AS1 could efficiently remove ammonia under a wide range of environmental conditions, including the ratio of chemical oxygen demand to total nitrogen: 15–30, pH: 6–10, NaCl: 0–60 g/L, shaking speed of 0–180 rpm, and succinate, acetate, or citrate as carbon source. In the treatment of actual piggery wastewater, 95.3%, 95.1% and 84.9% of NH 4 + -N was removed by AS1 when the initial ammonia concentration was 500, 1300, and 2000 mg/L, respectively, with the maximum NH 4 + -N removal rate of 30.5 mg/L/h and 569.7 mg/L/d. Furthermore, plate colony-counting showed that AS1 achieved an efficient proliferation. These results imply the application potential of AS1 in treating high-ammonia wastewater.