Biological treatment of high NH4+-N wastewater using an ammonia-tolerant photosynthetic bacteria strain (ISASWR2014)

Wastewaterwith high NH₄⁺-N is difficult to treat by traditional methods. So in this paper, a wild strain of photosynthetic bacteria was used for high NH₄⁺-N wastewater treatment together with biomass recovery. Isolation, identification, and characterization of the microorganism were carried out. The strain was inoculated to the biological wastewater treatment unit. The impacts of important factorswere examined, including temperature, dissolved oxygen, and light intensity. Results showed that photosynthetic bacteria could effectively treat high NH₄⁺- Nwastewater. Forwastewaterwith NH₄⁺-N of 2300 mg · L^-1, COD/N=1.0, 98.3% of COD was removed, and cell concentration increased by 43 times. The optimal conditions for the strain's cell growth and wastewater treatment were 30 ℃, dissolved oxygen of 0.5-1.5 mg · L^-1 and a light intensity of 4000 lx. Photosynthetic bacteria could bear a lower C/N ratio than bacteria in a traditionalwastewater treatment process, but the NH₄⁺-N removal was only 20%-40% because small molecule carbon source was used prior to NH₄⁺-N. Also, the use of photosynthetic bacteria in chickenmanurewastewater containingNH₄⁺-Nabout 7000mg· L^-1 proved that photosynthetic bacteria could remove NH₄⁺-N in a real case, finally, 83.2% of NH₄⁺-N was removed and 66.3% of COD was removed.