Effect of different extra carbon sources on nitrogen loss control and the change of bacterial populations in sewage sludge composting

The aim of this study was to evaluate the effect of different extra carbon sources on nitrogen loss control and the change of bacterial populations in sewage sludge composting. Four amendments, glucose, sucrose, starch and cellulose, were applied into the composting experiments conducted in the lab-scale reactor. The variation in temperature, pH, nitrogen content and bacterial population related to nitrogen transformation were detected during the 33 days composting. The addition of glucose, sucrose and starch reduced nitrogen loss and denitrifying bacteria population while increased the population of ammonifying, ammonia assimilating and nitrifying bacteria. Nitrogen loss was reduced by 24.7%, 46.3% and 26.5% in glucose, sucrose and starch treatments, respectively. The population of ammonifying, ammonia assimilating and nitrifying bacteria increased by 6.8-22.7%, 2.1-19.4%, 3.3-16.0%, respectively. Sucrose was the optimal amendment due to the lowest nitrogen loss (15.87%), the highest population of ammonia assimilating (7.0 log₁₀ cfu/g) and nitrifying bacteria (5.6 log₁₀ cfu/g). The results suggested that adding carbon sources in sludge composting could reduce nitrogen loss through improving the population of ammonifying, ammonia assimilating, nitrifying bacteria and reducing the population of denitrifying bacteria.