Impact of leachate recirculation frequency on the conversion of carbon and nitrogen in a semi-aerobic bioreactor landfill

摘要

To study the impact of leachate recirculation frequency on the transformation of carbon and nitrogen pollutants in a semi-aerobic bioreactor landfill (SABL), three laboratory-scale SABLs were investigated, each using a different leachate recirculation frequency (daily, once each 3days, and once each 5days). Results showed that degradation of total nitrogen (TN), ammonium nitrogen (NH4+-N), chemical oxygen demand (COD), and total organic carbon (TOC) could be described using a quadratic polynomial-compound index model. Degradation rates of TN, NH4+-N, COD, and TOC slightly increased from 0.01795, 0.01814, 0.01451, and 0.01166day(-1) to 0.02054, 0.01903, 0.01488, and 0.01203day(-1), respectively, when the recirculation frequency increased from once per 5days to once per 3days. When recirculation frequency was increased to daily, degradation rates of TN, NH4+-N, COD, and TOC significantly increased to 0.03698, 0.02718, 0.02479, and 0.02872day(-1), respectively. Moreover, when recirculation frequency increased from once per 5days to once per 3days, the gasification rate of nitrogenous and carbonaceous pollutants was enhanced between 20.38 and 8.17%, respectively. When the leachate recirculation rate further increased to daily, only a small amount of carbonaceous and nitrogenous pollutants was transformed to the liquid phase. Thus, increasing the leachate recirculation frequency in an SABL benefits the removal of carbonaceous and nitrogenous pollutants from the reactor. In addition, the greater is the recirculation frequency, the lower is the residual carbon and nitrogen in the solid phase, and the higher is the gasification rate. A proper recirculation frequency promotes the stabilization of landfill leachate. This study provides a theoretical reference and experimental evidence for accelerating the stabilization of MSW and contributes to the macro-control of landfills.