Technology Comparision And Feasibility Analysis Of Aged Landfill Leachate Preprocessing

The explosion of aged landfill leachate caused intractable problems for subsequent biological nitrogen removal.Xingfeng landfill treatment plant,located in Guangzhou,has 100000 m~3 of aged landfill leachate inside its regulating tank and been in full-loaded operation for a long time,which would be a great threat to safety and environment.Because of its restricted processing capacity,there is four thousand tons of aged landfill leachate transferred to the sewage plants located at downtown or surrounding area to be treated every day in emergency.Highly concentrated ammonia nitrogen of the aged landfill leachate would affect the normal operation of the sewage treatment technology if it is mixed into sewage plants directly.Proper water feeding pattern and necessary pretreatment are needed to relieve load shock and reduce ammonia nitrogen in the inflow.Therefore,this paper compared processing methods including aeration stripping,coagulation-flocculation plus advanced oxidation,magnesium ammonium phosphate precipitation,sodium hypochlorite oxidization,iron-carbon micro-electrolysis with simulation experiments under practical working conditions.Comparison and selection of economic feasibility was conducted in consideration of treatment effect and operation cost and it presented that coagulation-flocculation plus advanced oxidation was the optimal way for pretreatment.According to the results of pilot scale test,coagulation-flocculation plus advanced oxidation method could reduce the mean concentration of COD,ammonia nitrogen and total nitrogen from 4726mg/L、2402mg/Land 2464mg/L to 205mg/L、275mg/L and 291mg/L,under the dosage of 4.30kg/ton PAC、0.07kg/ton PAM and 0.69kg/ton calcium hydroxide,3600g,3600~5400g/h and 1800~3600g/h of ozone occurrence quantity,0.2kw and 1.8kw of photo catalysis work rate,1h,2h and 1.5h of HRT in advanced oxidation equipment,NO.1oxidation-cycling-separating tank and NO.2 oxidation-cycling-separating tank,average removal rate reaching 95.7%、88.6%and 88.2%.the variable operation cost was estimated to be 48.87 Yuan/m~3(including sludge treating fee),which is relatively cheap and possible to be less.According to the results of further bench-scale test,the ratio of the landfill leachate mixing into the sewage plants could increase to 1.0%from 0.3%by preprocessing with coagulation-flocculation plus advanced oxidation,with TN,the leading indicator of out flow,being unaffected,which showed that landfill leachate capacity could be improved to 333%.Production and operation data of many sewage plants were selected to ensure the rationality and scientificity of the preprocessing project,and the preprocessing scheme was designed according to practical conditions including the effect on transportation,available land area and the effective volume of regulating tanks.After preprocessing of coagulation-flocculation plus advanced oxidation method,it is predicted to take 40 days to treat the aged landfill leachate in Xingfeng landfill treatment plant.Based on the financial analysis,this project could generate 4.9936 million Yuan annually in leasing model and the payback period is less than 4 years.The implement of the landfill leachate preprocessing project could also bring about remarkable social and environmental benefit and solve the environmental problem and safety risk caused by excessive storage of landfill leachate,which is of great significance to the strategy of urban environment protection.