Electrochemical Treatment Of Biologically Treated Leachate From Municipal Solid Waste Incineration Plant And Environmental Medical Assessment Of The Process

The treatment of municipal solid wastes （MSW） represents one of the mostimportant problems of the modern society. In china, more than one billion tons ofMSW are produced every year. With the depletion of resources and the recycling ofwaste, people began to pay attention to the reuse of MSW, and incineration is aneffective technology for MSW disposal with its advantages. However, MSW leachateis a secondary pollutant from municipal solid waste incineration plants （MSWIP），andbe provided with the characteristics of black smelly, complex components, higherrecalcitrant organic compounds and NH₃-N. Leachate contains a large number of toxicorganic compounds which can cause the hazard of carcinogenic, teratogenic, andmutagenic. Leachate with inadequate treatment will destroy the environment, hurt thehealth of people，and MSWIP is facing technical problems of purifying MSW leachate.In industry, biological treatment always be used for pretreatment of leachate, butleachate after pretreatment still contains high COD, NH₃-N, need to take advancedtreatment with other physical or chemical method.With the advantages of operation at room temperature and atmospheric pressure,oxidizing organic pollutants into CO₂and the reaction can be terminated in secondsby cutting off the power; electrochemical oxidation has been widely investigated as anefficient means of controlling pollution in wastewater treatment. This work focuses onthe harmless treatment of MSW leachate after bio-treatment, and indirect oxidationwas used with the characteristics of high concentration of chloride ions in the MSWleachate. In order to simulate the actual industrial process, an electrochemical reactorwhich can continuously treat MSW leachate was designed, structure parameters ofreactor were optimized, and the energy consumption of the electrochemical reactorwere evaluated, so as to realize the low cost of waste leachate treatment and resourceutilization.In this work, the effects of operating parameters of current density, flow velocity,initial chloride ion concentration, and electrode gap on COD/NH₃-N removal wasstudied. It is shown that it is a good technology to treat leachate, under the operatingconditions of65.35mA·cm^-2current density,2.72cm·s^-1flow velocity,5000mg·L^-1initial chloride ion concentration and10mm electrode gap,90%of the COD in thelandfill leachate was removed after electrolysis for60min with a duplex Ru-Ir oxide-coated titanium （Ti/RuO₂-IrO₂） anode. The effects of operating parametersincluding electrolysis time, specific electrode surface, and sedimentation time afterelectrolysis on Colloid removal was investigated. It is shown that the filtration fluxwas obviously improved after the electrochemical treatment under the optimumconditions. GC-MS technique was used to detect components of organic pollutants inMSW leachate after bio-treatment, and the mechanism of degradation of organicpollutants was investigated. It was found that86kinds of organic pollutants wereidentified in the MSW leachate after bio-treatment,46kinds of organic pollutantswere removed after electrolysis for60min, and many chlorinated organics were foundin the wastewater after electrolysis. Finally, the acute toxicity of wastewater tozebrafish was determinated, the results show that MSW leachate after bio-treatmentand wastewater after electrolysis have acute toxicity to zebrafish, and the wastewaterafter electrolysis has more acute toxicity than MSW leachate after bio-treatment. It iscaused by chlorinated organic matter generated in the electrochemical oxidationprocess.This paper includes four parts of reactor design, optimization of processparameters, process mechanism analysis, and environmental toxicity evaluation toexplore the feasibility of electrochemical oxidation method for leachate treatment.This study shows that electrochemical method can well remove the COD, NH₃-N,chroma, colloid from leachate, the whole process can be simply operated,conveniently controlled, and the broad prospects for industrial applications. Theelectrochemical oxidation method is promising for industrial applications ofwastewater treatment.