Research Of Pretreating The Landfill Leachate By Advanced Oxidation Joint Struvite Precipitation

Along with the rapid development of China's economy and the improvement of people's living standards, urban garbage output increased rapidly. Landfill treatment was used in most cities of China, resulting problems of leachate treatment have become increasingly serious. The main features of leachate pollution were the complex components, high levels of pollutants, toxic, malodorous and difficult to use biochemical process directly. Therefore, in order to improve the leachate to the biochemical treatment standards, pretreatment is very important. In this context, we study the advanced oxidation?potassium permanganate, sodium hypochlorite and Fenton reagent?, magnesium ammonium phosphate chemical precipitation and joint this two methods of pretreatment of landfill leachate, aimed to find a efficient and economical processing technology to provide data support and theoretical guidance for effective treatment of leachate,. The main contents of this paper include the following aspects:?1? Pretreatment of Landfill by advanced oxidation. Three kinds of oxidants was respectively used?potassium permanganate, sodium hypochlorite and Fenton reagent? to pretreatment of leachate. The optimal reaction conditions of potassium permanganate was: dosage of 15 ml / L, pH value of 6.0, the reaction time of 80 min, when the maximum removal of leachate contaminants: color 68.09%, PO₄^3-99.98%,NH⁴⁺ 17.93%,CODCr 53.39%; The optimal reaction conditions of sodium hypochlorite was: dosage of 40 ml / L, pH value of 8.0, the reaction time of 60 min, when the maximum removal of leachate contaminants: color 54.73%, PO₄^3-99.97%,NH⁴⁺ 38.07%,CODCr 60.51%; The optimal reaction conditions of Fenton reagent was: ferrous chloride dosage of 4g / L, pH value of 3.0, the reaction time of 100 min, when the maximum removal of leachate contaminants: color 85.95%, PO₄^3-99.98%,NH⁴⁺ 6.75%,CODCr 63.87%.In the study of reaction kinetics, the rates of CODCr reaction was closer to third kinetic model when potassium permanganate used as an oxidant. When use sodium hypochlorite, the ratio of CODCr reaction was like the third kinetic model. When use Fenton reagent, the ratio of CODCr reaction was like the third kinetic model too.?2? Pretreatment of Landfill by magnesium ammonium phosphate chemical precipitation. Magnesium ammonium phosphate chemical precipitation method can be effective used to pretreat NH⁴⁺ in landfill leachate, and the remained PO₄^3- in the output water is very low. The optimal reaction conditions as follows: molar ratio of [Mg²⁺]/[NH⁴⁺]/[PO₄^3-] of 1.2: 1: 1.4, pH value of 9.5, the reaction temperature of 20?, the acting time of 15 min, the standing time of 20 min. Under the above conditions, the maximum removal of leachate contaminants: NH⁴⁺ 98.87%,CODCr 45.59%. Concentration of PO₄^3- remaining in the water after the reaction was 64.43 mg / L. In the kinetics of the reaction, the ratio of NH⁴⁺ reaction was closer to first kinetic model.?3? Pretreatment of landfill leachate by oxidants-struvite. Potassium permanganate-struvite, sodium hypochlorite-struvite and Fenton reagent-struvite was used to pretreat landfill leachate. Under the optimum conditions, the color, PO₄^3-, NH⁴⁺ and CODCr efficiencies of landfill leachate using potassium permanganate-struvite were:color 85.79%, PO₄^3- 47.20%,NH⁴⁺ 96.08%, CODCr 81.82%; The color, PO₄^3-, NH⁴⁺ and CODCr efficiencies of landfill leachate using sodium hypochlorite-struvite were:color 81.63%, PO₄^3- 61.49%,NH⁴⁺ 95.56%, CODCr 82.67%; The color,PO₄^3-,NH⁴⁺ and CODCr efficiencies of landfill leachate using Fenton reagent-struvite were:color 93.95%, PO₄^3- 70.80%,NH⁴⁺ 96.36%, CODCr 89.12%. Lastly, Fenton reagent-struvite was the best of combination method to pretreat.the landfill leachate.