Treatment of ammonia and nitrite in aquaculture wastewater by an assembled bacterial consortium

Abstract

The presence of high concentrations of ammonia, nitrite, and nitrate is a big challenge for the aquaculture industry to sustain fishery production, hence need to be treated in an economically feasible and environmentally friendly way. In the present study, a consortium of three bacterial isolates I4, I6, and I12, identified as Bacillus cereus, Bacillus amyloliquefaciens, and Pseudomonas stutzeri respectively, were assembled for the biodegradation of ammonia and nitrite in aquaculture wastewater. The consortium was employed as a bioaugmentation agent in tanks stocked with Oreochromis mossambicus fingerlings. During the experimental period of 15 days, under controlled conditions of temperature and light, the values of tested parameters were found to be increasing in both treatment and control tanks. The residual concentration of ammonia in the tanks treated with the consortium was always lower (4.8 ± 0.068 μML−1) than that of the control tanks without any bacteria (7.29 ± 0.292 μML−1). Increased residual concentration of nitrite and nitrate in the treatment tanks (6.9 ± 0.59 and 4.16 ± 0.58 μML−1 respectively) compared to the control tanks (0.28 ± 0.201 and 0.394 ± 0.964 μML−1 respectively) confirmed the efficiency of the consortium to convert ammonia to nitrite and further to the less toxic nitrate. Moreover, their values were never reached to the toxic level in the treatment tanks with a survival rate of 97.2 ± 0.58%, whereas in the control tanks death of fishes due to ammonia toxicity was observed (55 ± 0.25%). The study proved that the microbial consortium of Bacillus cereus, Bacillus amyloliquefaciens, and Pseudomonas stutzeri was efficient in reducing ammonia, nitrite, and nitrate in aquaculture wastewater and hence can be employed as a bioaugmentation agent to above-mentioned parameters in the aquaculture wastewater before discharging into the open system to reduce the environmental problems as well as to reuse the water.