Technical Research On Advanced Treatment Of Refractory Organic Wastewater

With the improvement of people’s living standards, processing and manufacturingindustries are developing rapidly. Meawhile, more and more refractory organic pollutantshave beenmassively discharged into the environment, resulting in a series of pollution. In thisthesis, xylose wastewater, kitchen wastewater and landfill leachate were adopted as theresearch objects. The degradation of xylose wastewater and the removal of chromogenicmaterial in xylose wastewater were firstly studied; and thenthe process of Fenton in treatingkitchen wastewater was discussed; eventually a modified tandem circulating fluidized Fentonoxidation tower was successfully trial-produced.Firstly, for xylose wastewater, the effects of the initial pH, H2O2, Fe2+dosage andreaction time on removal of COD, TOC and chroma in Fenton oxidation process wereinvestigated. The optimal reaction conditions obtained were as follows: pH value was3.5,H2O2dosage was80mg/L, Fe2+dosage was80mg/L, and the reaction time was30min.Under the optimum conditions, the removal rate of COD, TOC and chroma could reach up to81.0%,79.2%and90.6%, respectively, and the corresponding valuesin treated xylosewastewater were24.7mg/L,16.5mg/L and30, respectively, reaching the IntegratedWastewater Discharge Standard (GB8978-1996) of a standard limit requirements. Meanwhile,gas chromatography-mass spectrometry (GC-MS) was exploited to analyse the compositionof organic compounds in the xylose wastewater. The results showed that there wered at least70kinds of organics in the xylose wastewater, dominated by benzene as well as its derivativesand ketone aldehyde. Therefore, conventional biological treatment method is difficult to befully processed. In addition, the chromogenic material mainly comprised benzene-containingsubstances such as toluen, ethylbenzene,2,4,5-trichloro-toluene, naphthalene and2,4-di-tert-butyl phenol, acids such as oleic acid, aldehydes such as decanal and fourteenaldehyde. Under optimal conditions,the treatment cost of xylose wastewater using Fentonprocesswas about1.08yuan per ton.Secondly, for the kitchen wastewater, the optimal reaction conditions under the reactiontime of120min were as follows: Fe2+dosage was700mg/L, H2O2dosage was1300mg/L, pHvalue was4. COD and TOC were233mg/L and90mg/L respectively after treatment,reaching Integrated Wastewater Discharge Standard (GB8978-1996) Table III standards4,accordingly, the removal rates of COD and TOC were75.8%and71.1%, respectively. Theanalysis results showed that the treatment of kitchen wastewater by Fenton was the reults ofoxidation and flocculation. The oxidation was enhanced by the H2O2and reaction time.Meanwhile, the flocculation was improved by increasing the dosage of Fe2+and pH values,however, the oxidation reduced. The effect of oxidation: pH> H2O2> Fe2+, The effect offlocculation: Fe2+> pH> H2O2.The analysis results of organics by GC-MS showed that typesand quantities of organic matter were substantially reduced after Fenton treatment,demonstrating that the Fenton method would be an excellent alternative for removal oforganics in Kitchen wastewater. Finally, landfill leachate was treated by a trial-produced Fenton fluidized bed reactor, thebest treatment conditions achieved were H2O2dosage of322mg/L, Fe2+dosage of300mg/L,pH value of4, the effluent COD98mg/L, reaching integrated Wastewater DischargeStandard (GB8978-1996) for a standard limit requirements. The total COD removalefficiency was82.9%, where the COD removal in the2nd column was higher(about8%) thanthat in the1st column, This improvement would be attributed to the residual H2O2outflowingfrom1st column to the2nd column. The organic matter in leachate was analyzed usingfluorescence spectroscopy, and the results showed that the dissolved organic matter weremainly fulvic acid and humic substances. After treatment in Fenton fluidized bed reactor, thefluorescence intensity of humic substances considerably reduced from1005.0to283.3, andthat of fulvic acid substances decreased from696.2to207.4, which indicated that humic andfulvic acids could be partially removed by Fenton, or probably converted into a substancewith no fluorescence. Furthermore, the COD, TOC and UV254of DOM and humus intheinfluent and effluent were analized. The results showed that tandem circulating Fentonwould be a perfect alternative for removal of COD, TOC and UV254of DOM and humus inlandfill leachate, among which the removal of UV254was the highest, further illustrating thatFenton process was usefull for removing the aromatics in organic matter.