The Co-treatment Technology Of Leachate From Three Gorges Resvior With Domestic Wastewater By CASS Process For Discharge Under The Standards

Landfill leachate contains high concentration of organic pollutants including a large number of refractory organic and toxic substances,which will be harmful to the environment.Co-treatment of leachate and domestic wastewater may save the construction cost of landfill leachaate treatment facility,and reduce operating cost by simplifying management.In addition,mixing leachate to domestic wastewater with appropriate ratio may provide dilution,buffering effect and nutrients to domestic wastewater if leachate can blend in wastewater treatment plant properly and the plant can meet the standards.Three Gorges Reservoir is located in the mountains of Sichuan,Hubei and the junction of Canyon district,which are economically underdevelopment areas.There are many environmental problems in those areas. The experiment use CASS process which has the advantages of the simple process,effect and stability, small size, low investment and operating costs, resistance to shock loading and the perfect capability of removing nitrogen and phosphorus as the reactor for the research on co-treatment of leachate and domestic wastewater. Through studying the optional mixing ratio of the direct mixture of landfill leachate and domestic wastewater and the mixture of landfill leachate by magnesium ammonium phosphate precipitation (MAP) pretreatment, corresponding to the optimal mixing ratio the maximum potential volume loading of CASS process, the best operating parameters of improving the maximumum volume loading of co-treatment of the direct mixture of landfill leachate and domestic wastewater by CASS process,and research the technology of leachate by co-treatment of domestic wastewater on satisfying discharge standards. This research may provide a low cost and efficient technique to support low-income areas to treat leachate.There is an important practical significance on the protection of reservoir water environment.The main conclusions are as follows:①When domestic wastewater was mixed with 0.50% leachate directly, it reached the critical mixing ratio.The concentrations of the effluent CODcr, ammonia nitrogen,TN, and TP were 26.50mg/L, 2.42mg/L, 24.90mg/L, and 3.34mg/L,respectively. ②When domestic wastewater was mixed with 1.00% MAP-pretreated leachate, it reached the optimal mixing ratio, the concentration of the effluent CODcr, ammonia, and TN were 27.60mg/L, 0.68mg/L, and 15.85mg/L,respectively.③When domestic wastewater was treated with the critical mixing ratio of landfill leachate and domestic wastewater with 0.50%, the entry loading was 0.16CODcrkg/(m~3·d),0.0016TNkg/(m~3·d). When the domestic wastewater was treated with the optional mixing ratio of MAP-pretreated leachate and domestic wastewater with 1.00%, the entry loading was 0.19CODcrkg/(m~3·d),0.0268TNkg/(m~3·d).④When the aeration time was 3h and sludge return ratio was 80% and hydraulic retention time was 4.2h and dissolved oxygen was 2.00mg/L-2.50mg/L,the maximum potential of the entry loading was 0.0115TNkg/ ( m~3·d ) when CASS directly co-treatmented leachate and domestic wastewater.