Oxidation of ammonia with three bacterial strains belonging to genus Bacillus isolated from pig-farm wastewater after biogas tanks

Abstract

The biological removal of ammonia plays an essential role in the wastewater treatment technology. The oxidation of ammonia is the first step converting ammonia to nitrite, which is then transformed to nitrate as an intermediate substance and finally biotransforming to free nitrogen. A variety of bacterial strains with the ability to oxidation of ammonia were published. In this study, three ammonia-oxidizing bacterial strains were isolated from wastewater after biogas tanks of industrial pig farms in Ha Tinh province, named Bacillus megaterium HT1, Bacillus licheniformis HT1, and Bacillus subtilis HT1. The biotransformation of ammonia was monitored by the spectrum analysis method. The optimal pH and temperature for the three isolates’ growth are 7–7.5 and 30–37 °C. They can oxidize ammonia with a concentration of up to 750 mg/L within five days of incubation, and their ammonia-oxidizing rate is proportional to the concentrations of ammonia tested. The bacteria work well in the medium containing NaCl at a concentration of 3%. Besides, the low level of DO (0.1 mg/L) does not significantly affect their growth and ammonia-oxidizing activity. The results of this study can contribute to the diversity of ammonia-oxidizing bacteria and bring great potential to apply them to treat ammonia in wastewater.