Simultaneous removal of urea nitrogen and inorganic nitrogen from high-salinity wastewater by Halomonas sp. H36

To treat high-salt urea wastewater by microbial hydrolysis, it is necessary to overcome the dual problems of incomplete removal of nitrogen (N) from mixed strains and inhibition of microbial activity by high salt (NaCl) concentrations. In this paper, the mechanism of NaCl tolerance of Halomonas sp. H36 was investigated. Using molecular biology and enzymatic methods, it was proven that the strain's N-removal enzymes (urease; ammonia monooxygenase, AMO; nitrite reductase, NIR; nitrate reductase, NAR) played a key role in the removal of N, and the N-removal pathway was clarified. For the strain used to treat simulated ship domestic sewage, the urea nitrogen (CO(NH₂)₂-N)-removal rate was 88.52%, the ammonia nitrogen (NH₄⁺-N)-removal rate was 91.16%, the total nitrogen (TN)-removal rate was 90.25%, and nitrite nitrogen (NO₂^--N) and nitrate nitrogen (NO₃^--N) did not accumulate. It was proven for the first time that Halomonas sp. H36 has the function of simultaneous urea hydrolysis-nitrification-denitrification with urea as the initial substrate and can simultaneously remove urea nitrogen and inorganic nitrogen from high-salt urea wastewater.