Landfill Leachate Oxidation By UV And Heat Activated Persulfate Systems

Landfill leachate is characterized by high chroma,complex pollutant composition,and high pollutant concentration,posing a serious threat to the environment.Traditional biological treatment methods,such as membrane bioreactor（MBR）,possess certain limitations like low biodegradability during landfill leachate treatment.Therefore,advanced oxidation process is commonly applied for advanced treatment of bio-treated landfill leachate.In this study,the Heat/PS,UV_254nm/PS,UV_365nm/PS,and PMS systems were applied in landfill leachate treatment as the main PS-AOPs and PMS-AOPs.The efficiency and mechanism in removing chemical oxygen demand（COD）and ammonia nitrogen（NH₄⁺-N）in the MBR effluent of landfill leachate were evaluated.In addition,the application potential of these technologies was analyzed through biotoxicity and economy.In this research,the kinetic degradation of COD,NH₄⁺-N,TN,and chroma in the MBR effluent treated by Heat/PS,UV/PS,and PMS systems were systematically compared.Advanced persulfate oxidation method can effectively remove COD（initial 350-450 mg/L）,NH₄⁺-N（initial 65-85 mg/L）and chroma（initial 450-550 PCU）from the MBR effluent of landfill leachate.In Heat/PS system,when m（PS）₀=8940 mg/L and reaction temperature was70℃,the removal efficiency of COD,NH₄⁺-N,and chroma was 78.5%,99.6%,and 99.8%,respectively.In UV_254nm/PS system,the removal efficiency was 74.6%,99.0%,and 98.6%,respectively.In UV_365nm/PS system,the removal efficiency was 81.7%,96.8%,and 98.6%,respectively.In PMS system,when m（PMS）₀=20360 mg/L,the removal efficiency was 78.3%,97.3%,and 84.4%,respectively.The organic compounds in MBR effluent were mainly alcohols and alkanes,accounting for 36.2%and 33.6%respectively.There was no obvious change in the concentration after advanced persulfate oxidation.Organic matter analysis experiments showed that small organic matter with molecular weight less than 5 k Da was degraded preferentially in three systems.The removal efficiency of humic acid（HA）and fulvic acid（FA）was higher than99.0%.The inhibition rate of algae growth was more than 50%after the treated MBR effluent was diluted 10 times,which was considered as highly toxic,mainly due to the residual oxidant and low p H（≈3.5）.The economic analysis suggested that the lowest EE/O（Electrical energy per order）values of Heat/PS,UV/PS and PMS system were 1045,19490,and 4512k Wh·m^-3·order^-1,respectively.In addition,the effects of residual PS and PMS on the detection of common water quality indexes were quantified for the first time.It was found that PS and PMS could produce 3.3%and 1.3%interference to COD detection,respectively.The products of the reaction between PMS and Cl^-,such as Cl O^-,could also cause interference to the detection of TN（12.2%）.It is suggested that the secondary effects of PS/PMS on water quality at high doses should be investigated in future.