Methane and nitrous oxide emissions from a two‑stage membrane bioreactor applied in municipal landfill leachate treatment

摘要

The emissions of two major greenhouse gases, i.e., CH_4and N_2O,during the treatment of partially stabilized municipalsolid waste leachate by a practical-scale two-stage membrane bioreactor (MBR) were investigated. The system consisted ofanoxic and aerobic reactors that had a total hydraulic retention time (HRT) of 4 days and were operated with internal sludgerecirculation at 100% of the influent flow rate. At steady operation, high organic and nitrogen removals of 99% for BOD,97% for COD, 99% for TOC and 94% for TKN were achieved. During operation, high direct CH_4emissions from the anoxicreactor, accounting for 90% of the total emissions from the system and 16.2% of the total organic carbon mass removed, wereobserved. N_2Owas emitted to a much lower extent, and N_2Oemissions varied much less between the reactors. The presenceof methane- and nitrous oxide-producing bacteria was confirmed by PCR-DGGE and real-time PCR analyses. The operationof the two-stage MBR with sludge recirculation enabled the co-existence of CH_4-and N_2O-producing microorganismsin the sludge from the anoxic and aerobic reactors, with an approximately 30% difference in their microbial communities.