Hydroxyl radicals and reactive chlorine species generation via E+-ozonation process and their contribution for concentrated leachate disposal

Concentrated leachate is collected from two-stage anaerobic/aerobic-membrane bioreactor (MBR) and nanofiltration (NF) unit in landfill leachate treatment process and featured with non-biodegradation compounds and high salts content. E + -ozonation process was developed and introduced to deal with concentrated leachate, to make good use of chlorine ions (Cl − ) and the associated O 2 during ozonation process. 74.5% and 69.7% of COD and TOC were removed in E + -ozonation under the optimum conditions with initial pH of 9 and current density of 30 mA∙cm −2 , and the corresponding enhancement factors were 1.36 and 1.13, compared to the sum of the electrolysis and ozonation individual. The co-generation of reactive oxygen species (ROS) and reactive chlorine species (RCS) made a complementary effect on the degradation of refractory substances presented in concentrated leachate. 10.1% of total COD removal was improved by non-radical RCS generated in situ and 6.5% of total COD removal was achieved by ● OH-enhanced and Cl /ClO -emerged. With the help of electrolysis, the OH quencher of Cl − was converted into non-radical RCS (such as Cl − , ClO − and Cl 2 ) at anode, and the un-reacted O 2 /O 3 was reduced into OH at the cathode simultaneously. E + -ozonation offers a synergetic degradation potential for special wastewater with refractory matters and high Cl − content.