Research On Treatment Of Landfill Leachate By UASB And Fenton's Reagent Combination Process

Landfill leachate which was produced in sanitary landfill site isone of the high concentration organic wasterwater.Refuse in made upof complicated ingredients, such as organic and inorganic substancesand salt with some harmful heavy metals. In the process of handlingthe refuse has polluted the earth surface and underground the riversystem due to aversions fermenting, rain, surface running, immersingand vertical permeating. With the people's living level rising, therefuse contains much more organic ingredients than ever before. Thepoisonous of pollution has been doubled. The leachate has beenchanged greatly in nature with more complicated and interferedingredients.Since the complex of the leachate there is not perfect techniqueall over the world till now. The common processes are biologicaltreatment process and physical-chemical process. The biologicalprocess includes aerobic, anaerobic process and combination of bothprocesses. The biological process is effective for theammonia-nitrogen (NH₄⁺-N) and easy-biodegraded leachate.Furthermore biological process can't lead to second pollution and haslow cost. The physical-chemical process includes coagulation,deposition, adsorption, membrane, advance oxidation and so on. Thephysical-chemical process is not affected by the leachate quality andproduction. It is effective for the non-biodegraded leachate. Theadvance oxidation can degrade hart-treated substance more efficiency.With the help of past research experience the paper used a combinationprocess of UASB-Fenton reagents to treatment leachate.In the start-up stage of UASB reactor, the ranges of pH, CODCr andNH4+-N of the influent were 7.82⁸.51, 1040.4³416.2 mg/L and42.4⁹45.1 mg/L, respectively. The effluent CODCr and NH4+-N ranged156.7¹254.3 mg/L and 31.9⁸94.2 mg/L, respectively. The averageremovals of CODCr and NH4+-N of UASB reactor achieved 70% and 20%.In this stage the sludge take on floccule and flow out from the reactoreasy. In the stable operation stage of UASB reactor, the ranges of pH,CODCr and NH4+-N of the influent were 7.82⁸.51,3054.1³951.6mg/Land 763.5⁹45.1mg/L,respectively. The effluent CODCr and NH4+-Nranged 742.3¹248.7mg/L and 779.6⁹94.2 mg/L, respectively. Theaverage removals of CODCr and NH4+-N of UASB reactor achieved 70%and -4%. In this stage the reactor appeared some granular sludge. Theparticle size and machine intensity of the granular sludge is not enoughcompare with others reactor.The pilot-scaled study influence of HRT on the removal of CODCrand NH4+-N.While HRT of 12 hour the removal rate of CODCr is 58.7%.With the HRT raised to 48 hour the removal rate of CODCr up to 71.9%.Under the conditions of HRT of 96 hour and OLR of 0.91KgCODCr/(m3.d) the removal rate of CODCr exceeded 79.6%. It showsthat the influence of HRT on the removal of CODCr is reduced. Theinfluence of HRT on NH4+-N is not distinctly and sometime theconcentration of NH4+-N increase reversely after the anaerobic process.By the date of all it shows that the CODCr removal of UASB reactor forleachate is efficiency. But the removal of NH4+-N is not efficiency.Fenton's reagent is the oxidation system which structure byhydrogen peroxide(H2O2) and ferrous ion(Fe2+). Essentially, under theacidity condition hydrogen peroxide was catalyzed and analyzed to thehydroxyl radical that has high oxidation activity by ferrous ion. Andthen it induces and spreads a series of radical chain reaction. Highoxidative substances degrade organic compounds in aqueous solutionand accelerate the destruction of organic compounds and reductionsubstance. After the oxidation process we adjust the pH value to makethe solution take on alkali so that the ferrous ion can form ferrousflocculent precipitate which adsorb and removal heavy metal andresidual organic compounds. So the degrade effect of Fenton's reagentis the combination of the oxidation of hydroxyl radical and thecoagulation of ferrous ions. The advantage of Fenton's reagent fortreatment is strong oxidation, high treatment efficiency and no thesecond pollution bring.The paper takes the leachate after degraded by UASB reactor as thetreatment object of Fenton's reagent. The experiment study on thefactors of treatment affect which include initial pH, the concentrationof H2O2, the concentration of FeSO4·7H2O and reaction time. Thecharacteristic of influent is that 8.06 of initial pH, 984.6mg/L of CODCrand 841.7 mg/L of NH4+-N. Under the optimal conditions that initial pHwas 8.06, the quantity of H2O2 was 20mL/L, the quantity ofFeSO4·7H2O was 500mg/L,the stirring time was 15min and reactiontime was 60min. After treated by Fenton's reagent the effluent CODCrconcentration is 201.6mg/L. The removals of CODCr and chromaachieved 79.5% and 98%, respectively. Since the Fenton's reagent isone of effective method for leachate's advance treatment.The effect of UASB-Fenton combination process for treatmentleachate is better. And the total removal ratio of CODCr can achieve to95.8%. The effluent of CODCr can reduce to 201.6mg/L and agreed withthe second stage discharge standard of pollution control standard ofmunicipal sanitary landfill in China (GB 16889-1997). Unfortunately,the combination process can not remove NH4+-N of leachate effectiveand need further research.