Feasibility of using different hydrothermal processes for sewage sludge management in China

Due to its tremendous volume and severe environmental concern, sewage sludge (SS) management and treatment are significant in China. The recent prohibition (June 2021) of reusing SS as organic fertilizers makes it urgent to develop alternative processes. However, there is currently little research analyzing the applicability of using HP for sewage SS treatment in China. The significant difference in SS composition and the much less land supply in urban areas might invalidate most previous localized suggestions. In this paper, the development of emerging hydrothermal processes (HPs) for SS treatment will be reviewed, focusing on their decomposition mechanisms and the benefits of HPs com-pared with current SS treatment technologies. The SS volume, composition, and regulatory regime in China will also be evaluated. Those efforts could address the potential SS treatment capacity shortage and provide an opportunity to recover nutrients, organics and energy embedded in SS. The results show that HPs' high investment cost is mainly limited by the process scale, while their operating costs are comparable to incineration. Minimizing equipment ero-sion, ensuring process safety, and designing a more efficient heat recovery system are recommended for the future commercialization of HPs in China.

Automated summary

Due to its volume and environmental concerns, sewage sludge management and treatment are significant in China. The recent prohibition of reusing sewage sludge as organic fertilizers calls for the development of alternative processes. This study reviews the development of hydrothermal processes for sewage sludge treatment and evaluates the applicability in China, considering the differences in sludge composition and land availability in urban areas.