Effective treatment of leachate concentrate using membrane distillation coupled with electrochemical oxidation

[Display omitted] •Hybrid MD and EO was developed for treating the leachate concentrate.•The hybrid process was resistant to sharp declines during the initial stage.•Humic and aromatic substance were largely removed by the EO.•Antiscalant was effective for alleviating the scaling in long-term operation. The performance of sequential electrochemical oxidation (EO) and membrane distillation (MD) process was investigated for treating leachate concentrate with the characteristics of salinity and biorefractory organics. EO was achieved by direct and indirect oxidation on the Ti/PbO2 or Ti/Ru-Ir anode, by comparing the performance under different variations. Results showed that at an applied current density of 100 mA/cm2, operation time of 5 h and the choice of the Ti/PbO2 anode, the EO process could minimize the organic fouling by decomposing the larger molecular humic-acid that the removal efficiency was 83.4% for TOC. MD was used for treating the EO-pretreated concentrate due to its high rejection of salt and non-volatile components when treating salinity water. Flux results showed that the sequential system made the process resistant toward the sharp flux decline due to organics fouling, leading to a steady distillate flux in the earlier stage, and antiscalant was further added to retard the scaling in the long-time treatment. A strong interaction occurred between the foulants and antiscalant in the feed solution, and thus slowed down the scaling on the membrane which was reflected by the membrane flux, morphology and layer thickness. Results further showed that the ratio of actual and theoretical soluble Ca2+ was up to 61.6% and the energy barrier increased by 427.0% under optimum 20 mg/L PBTCA dosage. This study suggests that the sequential EO-DCMD system with antiscalant dosage can provide a potential alternative for treating the leachate concentrate.