Effect of enriched thermotolerant nitrifying bacteria inoculation on reducing nitrogen loss during sewage sludge composting

[Display omitted] •Enriched thermotolerant nitrifying bacteria was inoculated in sludge composting.•Inoculation reduced ammonia emission and improved the content of nitrate.•Inoculation increased population of nitrifying bacteria and enhanced nitrification.•Inoculation with TNB was a feasible method to reduce nitrogen loss during composting. In the study, enriched thermotolerant nitrifying bacteria (TNB) was acquired from compost samples by domesticated cultivation under high temperature, and was inoculated into sewage sludge composting. The effect of inoculation on physical-chemical parameters, nitrogen loss and bacterial population involved in nitrogen transformation were determined. The results revealed that inoculation with enriched TNB improved the compost quality in terms of temperature, pH, organic matter degradation, C/N ratio and germination index. Compared to the control treatment, inoculation also decreased 29.7% of ammonia emission and reduced nitrogen loss by converting more NH4+-N into NO3−-N in composting. In addition, inoculation increased the population of nitrifying bacteria and was not capable of inhibiting the growth of indigenous ammonifying bacteria as well. The results suggested that inoculation with enriched TNB was a feasible way to reduce nitrogen loss and promote maturity in sewage sludge composting.