Studies On Pretreatment Of Landfill Leachate By Coagulation-Adsorption Process

Landfill leachate has the characteristics of containing high concentration of COD, heavy metal and ammoniacal nitrogen. Traditional biological techniques can not make the treatment process run in gear. As the pretreatment of landfill leachate, physical chemistry techniques can reduce the biological toxicity so as to providing a good condition for following biological treatment. Therefore, it is significative to study on pretreatment of landfill leachate by physical chemistry techniques which can make great sense in theory and practice of engineering.This thesis studies on the pretreatment of the Chengdu Chang'an landfill leachate by coagulation-absorption process.Poly Aluminum Ferric Sulfate (PAFS) was used as coagulant in coagulation process. Considering that the effect of pH value, doses of PAFS, setting time and the other factors, the experiment was carried out by orthogonal design method. The result shows that, the pH of leachate affects most on the removal rate of COD, and doses of PAFS, setting time, also have effection on it. Under the best condition of the addition of PAFS at about 200mg/L, pH value about 8.0, setting time 40min, we can achieve the best outcome:the removal rates of CODcr is about 37.5%. But coagulation process with PAFS can not reduce ammonia-nitrogen in effect. The water after the coagulation process will be used in following adsorption processe.In phrase of absorption process, two kinds of cheap adsorbents were used in the experiment. By contrast, the removal of COD by absorption with peat coal was not content, but peat coal can absorb much ammonia-nitrogen from leachate. After 8 hours'absorption, about 66.34%ammonia-nitrogen removal was achieved. On account of its own structure and components, coal ash can reduce more COD and ammonia-nitrogen of leachate than peat coal does. The result shows that, the coal ash dosage with 50g/L can reduce 55.57%COD in leachate when the absorption of COD reaches saturation after 3 hours. The ammonia-nitrogen adsorbed by coal ash became more with time extended and its removal came to 96.34%or so after 8 hours adsorption. Meanwhile, the ammonia-nitrogen removal increased as the pH value rose.