Treatment Of Landfill Leachate By Microwave-assisted Persulfate Process

Landfill leachate is a kind of high concentrated organic wastewateryielding from the processes of MSW（municipal solid waste） landfill orpacking. Since the high concentration of pollutants, and complexcomposition, and the big fluctuation of quality and quantity, and posingpollution to the surrounding environment, especially threatening surfaceand ground water, the treatment of landfill leachate is always recognizedas the hotpot and difficulty in the sewage treatment field. The paper aimedto researching the treatment of landfill leachate using microwave-assistedpersulfate process. Firstly, by studying the treatment effect on the landfillleachate of several different microwave processes, including singlemicrowave, microwave/activated carbon and microwave-assisted persulfate,then analysis the role which the main factors of each process play in thereaction system, and made a preliminary analysis on the reactionmechanism of each process. Secondly, microwave-enhanced persulfateoxidation process using activated carbon as catalyst was applied to thedisposal of landfill leachate, including the orthogonal experiment, Singlefactor experiment, the comparison of treatment effect by differentprocesses, discussing the reuse performance of activated carbon, and themechanism of microwave/activated carbon/persulfate process were studiedby then. The conclusions of this paper could be found in the follows:(1) The removal rate of COD and NH4+-N increased with the increaseof microwave power、reaction time、activated carbon dosage and persulfatedosage in the single microwave process、 microwave/activated carbonprocess and microwave/persulfate process. The effect of pH value on CODremoval rate was unconspicuous while was appreciable on NH4+-N underalkaline condition.(2) Orthogonal experiment showed that the reaction time andmicrowave power had significant effect on COD removal rate, and thesecondary effects were persulfate dosage、 pH value and activated carbondosage respectively. The single factor test showed that the removal ratesof COD and NH4+-N were affected importantly by the factors of the activated carbon dosage, persulfate dosage, pH value, microwave powerand radiation time. The optimal condition was that: activated carbondosage=10g/L, S2O82-:12COD0=1.2, pH=9, microwave power=500W andradiation time=10min. Under the optimal condition, the rates of COD andNH4+-N removal were78.2%and67.2%respectively, and thebiodegradability (BOD5/COD) of the landfill leachate increased to0.38.(3) The results of comparison experiments showed that the removalrates of COD and NH4+-N in the process of microwave/activatedcarbon/persulfate were remarkable higher than the other treatments. Theremight be certain cooperation actions in microwave/activatedcarbon/persulfate system. In the experiment activated carbon recycling, theremoval rates of COD and NH4+-N decreased with the increase of thenumber of using activated carbon. After AC was used four times, theremoval rate of COD was61.2%, while the NH4+-N was46.1%. Methanol(MA) and tert-butyl alcohol (TBA) were applied as chemical probecompounds to detect the mechanism of free radicals in themicrowave/activated carbon/persulfate reaction system for oxidationtreatment of landfill leachate. The results showed that both SO4.-and OH.played roles in the process of COD degradation,but SO4.-played a majorrole.