Applicability Evaluation About Several Typical Physical And Chemical Pretreatment Technologies For Landfill Leachate

Landfill leachate contains great harmful pollutants including refractory organic matters, ammonia nitrogen, and heavy metals, how to treat it is one of the major problems of sewage treatment. Currently, there are two common leachate treatment methods in China: treating leachate with domestic wastewater in municipal wastewater treatment plant or treated it alone in landfill. Each treatment method needs leachate pretreatment. The principle of the pretreatment and operating parameters for the pretreatment have been studied by many researchers. However, the use of pretreatment technologies for different leachate qualities or for requirements of different treatment methods has not been reported. Therefore, selecting pretreatment of leachate often lacks convincing basis.In this study, five common physical and chemical pretreatment technologies: including aeration stripping, magnesium ammonium phosphate (MAP), Fenton oxidation, coagulation, stripping+coagulation were evaluated according to different landfill leachate (young and old) and different treatment methods (co-treated with domestic wastewater and treated alone). In addition, the pretreatment technologies were compared with regarding to operating costs to provide the basic information on the pretreatment technology options. The following conclusions were obtained:â‘ For the different landfill leachate, operating parameters for the optimum performance of each pretreatment technology are:Aeration stripping, pH10.5¹1.5, gas-liquid ratio 2000³000, the aeration time 3 4h;MAP, Mg²⁺: NH₄⁺1.2:1¹.4:1, reaction time 2h, stirring intensity 200r/min, NH4 +: PO43-1:1 1:1.2 (early) / 1:1.2 1:1.4 (late) ;Fenton oxidation, H2O2/Fe2 + 5:1 7:1, pH3 4, the reaction time 2.5h,H2O2 dosage 0.15 0.20 (early) / 0.1 0.15 (late) mol/L;Coagulating sedimentation, PAM dosage 10mg / L, pH 7 to 9, stirring intensity 80r/min, PAC dosage of 1200 1400 (early) / 1000 (late) mg/L.â‘¡For the effect of pretreatment. When old leachate was co-treated with domestic wastewater, aeration stripping + coagulation, MAP, and aeration stripping was recommended as pretreatment technology, the composite score was 6.11, 5.43, and 4.94, respectively. When old leachate was treated alone, stripping + coagulation, Fenton oxidation and MAP was recommended as pretreatment technology, the composite score were 5.63, 4.96, 4.88, respectively.When young leachate was co-treated with domestic wastewater, Stripping + coagulation, MAP, aeration stripping and Fenton oxidation was recommended as pretreatment technology, the composite score was 6.23, 5.95, 5.14, 4.54, respectively. When old leachate was treated alone, Stripping+coagulation, MAP, was recommended as pretreatment technology, the composite score was 5.02, 4.72, respectively.â‘¢As results of the analysis combining pretreatment achievement and operating costs, pretreatment options varies by the age of leachate and by leachate treatment options, aeration stripping were able to achieve certain pretreatment efficiencies with low operating cost, and more suitable when leachate co-treated with domestic wastewater, recommended as the preferred physical and chemical pretreatment; Although the MAP showed excellent pretreatment efficiency, the operating cost was very high, should not be used when economic conditions were not allowed. Fenton oxidation showed noticeable pretreatment efficiency,but the operating cost was high. So, Fenton oxidation could be considered to use for old leachate when treated alone in landfill and for young leachate when co-treated with domestic wastewater. Coagulation and sedimentation showed low operating cost, but the pretreatment efficiencies were low, recommended using with other pretreatment; stripping + coagulation were able to achieve excellent pretreatment efficiencies with low operating cost, recommended as the preferred physical and chemical pretreatment;...