Isolation, identification and characterization of heterotrophic nitrifying bacteria from surface water

For reducing ammonium concentration and guaranteeing safe drinking water, three heterotrophic bacteria were isolated from the Songhua River, which were SFA6, SFA7 and SFA11. When the initial ammonium concentration was about 130 mg/L, the ammonium removal rate of the strains SFA7, SFA6 and SFA 11 were 1.54 mg NH₄ ⁺/L/h, 1.20 mg NH₄ ⁺/L/h and 1.27 mg NH₄ ⁺/L/h respectively at 8 °C. The 16S rDNA sequence results revealed that the strain SFA6 was Bacillus subtilis, SFA7 was Pseudomonas putida, and SFA11 showed similarity to Pseudomonas nitroreducens. The biochemical characteristics of SFA6 were quite different from that of SFA7 and SFA11. After 48 h degradation, the NH₄ ⁺-N (about 5 mg/L) was consumed to 0.23±0.15 mg/L, 0.37±0.20 mg/Land 0.58±0.17 mg/L by the strains SFA6, SFA7 and SFA11, with little NO₃ ^--N and NO₂ ^--N accumulation. Above all, the strains SFA6, SFA7 and SFA11 could be used in drinking water treatment at 8 °C. The strain SFA6 showed the highest ammonium removal efficiency.