Leachate treatment using a demonstration aged refuse biofilter

Approximately 7000 m3 of aged refuse (AR) with a placement of over eight years was excavated from Shanghai Refuse Landfill, the largest landfill in China, and used for the construction of a two-stage bioreactor (AR biofilter) media for the biological treatment of 100 m3 of refuse landfill leachate. It was found that over 64% of COD, 96.9%–99.8% of NH4+-N, and 95.8%–99.8% of BOD5 could be removed by the AR biofilter, when the leachate with initial COD, BOD5, and NH4+-N concentrations were 986–4128 mg/L, 264–959 mg/L, and 538–1583 mg/L, respectively. The corresponding concentrations in the effluent were reduced to below 300–400 mg/L, 2–12 mg/L, and 10–20 mg/L, respectively. The effluent was clear and pale yellow with suspended solid below 150 mg/L and color below 150 Pt/Co degree. Meanwhile, the total nitrogen removal was only 49%–63%, indicating a relative poor denitrification capacity of AR biofilter. The effluent pH was neutral and the population of Escherichia coli was less than 10−1 CFU/mL. Hence, it was considered that the demonstration project can work well for the effective treatment of leachate.