Hydrothermal treatment of sewage sludge was conducted by using a stainless steel autoclave reactor at different temperature. This study aims to investigate the influence of reaction temperature on the migration and transformation of nitrogen in sewage sludge during hydrothermal treatment. The pathway of nitrogen transformation during hydrothermal treatment was also comprehensively analyzed. The results showed that nitrogen was mainly distributed into solid and liquid products after hydrothermal treatment. The percentage of nitrogen distribution in liquid products was increased with the increasing reaction temperature. During hydrothermal treatment

the inorganic nitrogen in sewage sludge was almost completely hydrolyzed to ammonia nitrogen and nitrates nitrogen. The labile protein was decomposed into organic nitrogen and ammonia nitrogen

and the organic nitrogen was further decomposed to ammonia nitrogen. However

the stable protein can be transformed into the forms of pyridine nitrogen

pyrrole nitrogen

quaternary nitrogen and nitrile nitrogen. Each form of nitrogen can be decomposed into ammonia nitrogen at a high reaction temperature. In summary

the nitrogen in sewage sludge was gradually transformed from solid products to liquid samples with the increasing hydrothermal reaction temperature

and the nitrogen remained in liquid samples major in the form of organ nitrogen and ammonia nitrogen.