Pretreatment Of Mature Landfill Leachate By Sulfate Radical-advanced Oxidation Process (SR-AOP)

In China, many municipal solid wastes (MSW) were disposed by sanitary landfill.However, the heavily polluted wastewater known as landfll leachate is also generatedwhen rain water percolates through waste layers in municipal landflls. Landfillleachate contains high concentrations of dissolved and suspended organic matter,inorganic compounds such as ammonia and heavy metals, which is considered as apotential source of contamination of the surrounding environments, especially the soiland the groundwater.The mature leachate shows the lowest biodegradability properties with biologi caloxygen demand/chemical oxygen demand (BOD/COD) ratio below0.1.The biologicaltreatment process has been unable to effectively degradade the mature leachate.Therefore, the physicochemical processes, as a pretreatment step to biologicalprocesses are usually used to improve mature leachate biodegradability. Leachatesamples used in this study were taken from the Hei Mi-feng sanitary landfill locatedin Changsha, south of China. The landfill leachate is treated by the persulfate reagent,ultrasonics and ultrasonic activated persulfate process. The optimum processconditions of the method are achieved using integrated Taguchi method and responsesurface methodology.The major achievements in this study are as follows:(1)The purpose of this experiment is to operate persulfate oxidation processefficiently. The COD, Color, UV254and TOC removal of the leachate by persulfateoxidation is68.25%,75%,68.64%,75.80%, respectively, under the followingconditions: the initial pH value is of4, the S2O82-/12COD0ratio is1and the reactiontemperature is60℃.(2)With increased ultrasound power input, landfill leachate UV254removal didnot change significantly. Therefore, the effect of ultrasonic irradiation power onUV254removal is not obvious.(3)According to the landfill leachate was treated by ultrasoni c activatedpersulfate, the different levels of the various factors has different effct on the TOCremoval. The results showed that the rank of grey relational grade for the TOCremoval is temperature (x3)> S2O82-/12COD0ratio (x1)> reaction time(x5)> radiationpower (x4)> initial pH (x2).(4) Through the integrated optimization using Taguchi method and responsesurface methodology, the optimal independent variables of sono-activated persulfate oxidation for landfill leachate were suggested as followings: S2O82-/12COD0of0.68,temperature of70℃and reaction time of2.46h. The experimental values for TOCremoval efficiency (75.88%) was in good agreement with the values predicted fromthe models (77.32%), with relatively small errors between the predict ed and the actualvalues.(5)The sono-activated persulfate oxidation exhibited better performance to themature landfill leachate than other AOP in term of TOC removal. And investigate theremoval of DOM under the optimum sono-activated persulfate oxidation conditions.The result also indicates that the enhanced TOC removal by ultrasonic activatedpersulfate oxidation should be attributed to the persulfate activated by thecomprehensive action of ultrasonic catalysis and heat.