Characterization and treatment of landfill leachate membrane concentrate by Fe(2+)/NaClO combined with advanced oxidation processes

Landfill leachate membrane concentrate (LLMC) is a type of non-biodegradable wastewater intercepted by the membrane filtration of the landfill leachate membrane bioreactor (MBR) effluent. The concentrations of chemical oxygen demand (COD) and ammonia nitrogen (NH(4)(+)-N) in the LLMC collected from a landfill in Beijing were determined to be 4700 mg/L and 487 mg/L, 2–5 times higher than those in the MBR effluent. The photoelectro oxidation (PEO) followed with the NaClO enhanced Fe(2+) coagulation were more effective for the removal of COD than the Fenton oxidation followed with the enhanced coagulation. The final removal efficiencies of COD, UV(254), NH(4)(+)-N and color degree were 86%, 95%, 93% and 95% with Fe(2+) (90 mmol/L) and NaClO (60 mmol/L, Fe(2+):NaClO = 1.5:1), and PEO for 3 hours with a current density of 400 A/m(2). Due to the existence of Cl(−), the chlorinated intermediates, which would be more toxic, were detected in the PEO treatment. However, the intermediates could be eliminated finally. As a result, the NaClO enhanced Fe(2+) coagulation treatment combined with PEO treatment was efficient for the treatment of LLMC.