Mechanism and molecular level insight of refractory dissolved organic matter in landfill leachate treated by electroflocculation coupled with ozone

Landfill leachate usually contains a substantial content of refractory dissolved organic matter (RDOM), which mainly consists of humic acid and fulvic acid. RDOM easily blocks the membrane pores resulting in membrane fouling when treated using membrane technologies, and it costs abundant chemical regents using advanced oxidation processes. To achieve the economically efficient treatment of RDOM in landfill leachate, this study established the electroflocculation coupled with ozone (EFCO) system. EFCO achieved a higher removal for organic matter than single electroflocculation and ozonation, where RDOM was the main component of organic matter in landfill leachate. The remaining RDOM was decomposed into lots of micromolecule weight and biodegradable proteins and lipids. Ozone improved the removal of dissolved organic matter (DOM) mainly by changing the functional groups on its surface and improving the mechanical strength of flocs to enhance the complexation between flocs and DOM. Cl₂⁻ and ClO produced in the EFCO system were the main active chlorine species, which enhanced the mineralization of RDOM. The study provides an efficient method for the pretreatment of RDOM in landfill leachate.