Impacts of adding thermotolerant nitrifying bacteria on nitrogenous gas emissions and bacterial community structure during sewage sludge composting

This study aimed to evaluate the impacts of inoculation with bacterial inoculum containing three thermotolerant nitrifying bacteria strains on nitrogenous gas (mainly NH₃ and N₂O) emissions and bacterial structure during the sludge composting. The results of physicochemical parameters indicated that inoculation could prolong the thermophilic phase, accelerate degradation of organic substances and improve compost quality. Compared with the non-inoculated treatment, the addition of bacterial agents not only increased the total nitrogen content by 8.7% but also reduced the cumulative NH₃ and N₂O emissions by 32.2% and 34.6%, respectively. The bacterial inoculation changed the structure and diversity of the microbial community in composting. Additionally, the relative abundances (RA) of bacteria and correlation analyses revealed that inoculation increased the RA of bacteria involved in nitrogen fixation. These results suggested that inoculation of thermotolerant nitrifying bacteria was beneficial for reducing nitrogen loss, nitrogenous gas emissions and regulating the bacterial community during the composting.