Membrane distillation combined with electrocoagulation and electrooxidation for the treatment of landfill leachate concentrate

[Display omitted] •Combined EC-EO-DCMD process is proposed to treat leachate concentrate.•EC-EO pretreatment can effectively remove organic matter and Ca2+/Mg2+ ions.•The membrane flux after EC-EO pretreatment is 23%∼42% higher than EC and EO alone. The landfill leachate concentrate is a kind of waste water containing salt and refractory organics produced by the membrane bioreactor-nanofiltration/reverse osmosis process. In the present work, three integrated processes of electrocoagulation (EC)-direct contact membrane distillation (DCMD), electrooxidation (EO)-DCMD and EC-EO-DCMD were used to treat the leachate concentrate. The results show that the total organic carbon (TOC), Ca2+ and Mg2+ removal rates of the EC process were 40.52%, 98.03% and 88.84%, respectively, under the optimal operating conditions. The TOC removal rate of the EO process was 64.62% under the optimal operating conditions. The removal rates of TOC, Ca2+ and Mg2+ by combined EC-EO process were 82.16%, 99.04% and 94.22%, respectively. When the MD was applied together with the EC and EO steps, the flux improved 23%∼42%, which was confirmed by the SEM-EDS, FTIR and XRD analysis that only quite a small amount of humic acid and fulvic acid substances was observed to be randomly deposited on the membrane surface. During 72 h operation, the permeate had a lower conductivity than 15 μS/cm, and only a small amount of organic (TOC