Study On The Pretreatment Technology Of Coagulation And Precipitation Of Landfill Leachate Membrane Concentrate

Landfill leachate is an important part of environmental pollution,and membrane treatment has gradually become the main technology in landfill leachate treatment.However,the leachate concentrate produced by membrane treatment is more difficult to treat than the leachate,which contains a large number of refractory pollutants and salts,and improper treatment will cause more serious environmental pollution.At present,the treatment technology of leachate membrane concentrate has been widely concerned by scholars at home and abroad,but the research mostly focuses on the deep treatment technology such as evaporation and crystallization of membrane concentrate,while the research on its pretreatment method is less.In this case,it is of great significance to discuss the concrete coagulation and precipitation pretreatment method for the treatment of membrane concentrate.In this paper,the membrane concentrate of landfill leachate from Taihang Landfill of Shijiazhuang Sanitary Waste was pretreated by coagulation sedimentation and adsorption,the main purpose of which was to ensure the stable operation of subsequent evaporation process and reduce the risk of scaling and blocking of evaporation equipment,so as to use"coagulation sedimentation pretreatment+low temperature atmospheric evaporation process"for overall effective treatment of the membrane concentrate.The effects of pH,dosages of different alkali,temperature,types and dosages of flocculant,combination of agents and adsorption conditions on the removal of scale and volatile pollutants were investigated in this article.COD_Crremoval rate,Ca²⁺removal rate,Mg²⁺removal rate,residual sludge and other indicators were selected to analyze the influence of different factors on the pretreatment effect and determine the optimal pretreatment reaction conditions.The results showed that COD_Cr、Ca²⁺and Mg²⁺concentrations of landfill leachate membrane concentrate can be effectively reduced by coagulation and sedimentation method,which is of great significance for the stable operation of subsequent evaporation process.（1）the optimal pH value of NaOH solution regulated the pH of leachate membrane concentrate was 11.The optimum pH value of Ca（OH）₂solution regulated the pH of leachate membrane concentrate was 11.The effect of temperature on the removal rate of COD_Crwas relatively weak,and the best experimental temperature was 25℃,that is,at room temperature;（2）Different flocculants were used to treat the membrane concentrate.When PAC,synthetic organic flocculant and PAM were combined,the optimal dosage was 1.5g/L PAC,3.5g/L synthetic flocculant and 0.01g/L PAM;（3）The removal rate of COD_Crwas significantly affected by different combinations of agentia,and the removal rates of Ca²⁺and Mg²⁺were generally higher."NaOH+Ca（OH）₂+Na₂CO₃+PAC+synthetic organic flocculant+PAM"combination was selected as the best agentia combination method.At this time,the removal rate of COD_Crwas57.39%;（4）The adsorption effect of powdered activated carbon was obviously better than that of biochar.When the combined method of“NaOH+Ca（OH）₂+Na₂CO₃+PAC+synthetic organic flocculant+PAM+powdered activated carbon”was used to treat the leachate membrane concentrate,the optimal dosage of powdered activated carbon was 20g/L,the optimal adsorption time under this dosage was 1.5h,the Ca²⁺removal rate and Mg²⁺removal rate were 99.57%and97.00%respectively,and the removal rate of COD_Cr was 60.77%.