Study on the advanced treatment for biological treat process of landfill leachate by precipitation/Fenton process

Precipitation-fenton process was used in the advanced treatment of landfill leachate after treated by biological process. The effects of the types and dosage of coagulant to the removal rate were discussed. It was found that the optimum coagulant was polyferric sulfate (PFS) with dosage 20 mL/L. In the orthogonal experiment, the effects of initial pH value, dosage of H_2O_2 and FeSO_4·7H_2O as well as the reaction time to the removal rate were studied. The initial pH value was found to be the main factor that affects the treatment performance. Later, the single factor experiments were performed and the results showed that the optimum conditions of fenton reaction are as follows: pH value is 3, dosage of H_2O_2 and KeSO_4·7H_2O are 3.0 mL/L and 3.5 g/L respectively, and the whole reaction time is 120 min. Under the mentioned condition, COD_(Cr) decreased from 560 mg/L to 93 mg/L and the removal rate was able to reach 83.4% which is matched with the revised national standard GB 16889— 2008. Ultraviolet-visible Spectroscopy was used to analyze the landfill leachate that pretreated by precipitation-fenton. The results showed that there are many large molecular organics and polyaromatic hydrocarbons in the landfill leachate. After the pretreatment, the large molecular organics were oxidized to smaller ones, CO_2 and H_2O. Thus, the precipitation-fenton process has been proven to be an effective pretreatment methodology for landfill treatment.