Environmental impact analysis of nitrogen cross-media metabolism: A case study of municipal solid waste treatment system in China.

Municipal Solid Waste Treatment System (MSWTS) contributes a lot to urban metabolism optimization and pollution control of nitrogen. An analysis framework for cross-media metabolism of nitrogen was developed for MSWTS to study the systematic effects of nitrogen metabolism in MSWTS on ecosystem quality. Then cross-media distribution of pollutants was calculated in landfill, composting, incineration and anaerobic digestion, respectively. Sixty three percent to 82% of the original inputs ended up in the natural environment using the former three technologies (landfill, composting and incineration), which was attributed to cross-media migration. Anaerobic digestion should be highlighted due to its overall desirable removal efficiency. Critical processes related to nitrogen cross-media migration were identified to analyze the overall environmental impacts sensitivities. Positive effects emerged in liquid-solid interface migration of nitrogen through sewage collection and treatment technology processes, while the incineration flue gas treatment witnessed negative effects in gas-liquid interface migration. Overall, the environmental impact sensitivity levels of nitrogen cross-media migration under critical processes were as follows: incineration>landfill>composting>anaerobic digestion. Therefore, the environment is most sensitively affected by incineration and its processes. The present study is of great significance to optimize environmental management by shifting the management mode from single environmental medium quality control to systematic ecosystem quality improvement.