| With the construction and operation of industrial wastewater secondarytreatment facilities, most of the pollutants in wastewater are degraded. However,the concern on the corresponding problem of refractory organics contaminationincreases significantly. The refractory organics could affect the safety of waterresource and damage the health of human. The advanced treatment of wastewaterfrom antibiotic pharmaceutical industries, especially from fermentationpharmaceutical plants as one of the most seriously polluting industries has beenthe concern focus. By comparation, the catalytical ozone oxidation technologywas chosen to oxidize the non-biodegradable organics. The catalytical ozonationtechnology （O3/GAC/H2O2） composited by modified granular activated carbonwith hydrogen peroxide was proposed in this study, while it can degrade therefractory organics in biologically treated effluent significantly. It can enrich thetheory of catalytical ozone oxidation about refractory organics and providetechnical support for advanced treatment of them in industry wastewater.The refractory organics in antibiotic pharmaceutical biologically treatedeffluent （BTE） were analyzed by Gas Chromatograph-Mass Spectrum （GC-MS）analysis. The highest amounts of organics were esters and aromatic hydrocarbonsin wastewater. According to High Performance Liquid Chromatography （HPLC）analysis, the dibutyl phthalate as one typical kind of Endocrine DisruptingChemicals （EDC） was the main pollutant in wastewater. Based on therelationship of Chemical Oxygen Demand （COD） and Theoretical OxygenDemand （ThOD）, the contributions of different organics to COD was evaluated,while the dibutyl phthalate and bis（2-ethylhexyl） phthalate were determined asthe typical pollutants because of their most contributions to COD in effluent.The O3/GAC/H2O2technology was composited by ozone, modified GACand hydrogen peroxide. According to the analysis of BET, Scanning ElectronicMicroscope （SEM）, Fourier Transform Infrared Spectroscopy （FTIR） and X-raydiffraction （XRD）, the high specific surface area of1010m2/g and theconcentration of surface basic groups of9.83410-6mol/m2were determined,while the complex tubular structures were found with amorphous carbon status in the modified GAC.The significant effect for DBP degradation was found by compositedprocess of O3/GAC/H2O2. The positive effects of factors of ozone concentration,gas flow rate, initial pH, reaction temperature and modified GAC dosage for DBPdegradation were investigated, respectively. The degradation efficiency increasedfirst, then decreased along with the increase of H2O2dosage. With the samedosage of applied ozone and H2O2, the multiple steps addition showed the higherdegradation efficiency than that obtained by adding within one step before thestart of the experiment.The degradation process of DBP in the catalytical ozone systemO3/GAC/H2O2was investigated to follow a second-order kinetic model. Theeffects of influencing factors, ie. ozone concentration, gas flow rate, H2O2dosage,initial pH, reaction temperature and modified GAC dosage, on the apparentreaction rate constant kappwere evaluated in the study. The positive correlationrelationships of kappwith influencing factors above were investigated, while thekappincreased first, then decreased along with the increase of H2O2dosage. Bycomparison analysis the initial pH was found to have greatest influence on thekappwith moderate influence of H2O2dosage and ozone concentration. However,the GAC dosage has the lowest influence on kapp.By means of multiple linearregression fitting, the kinetic practical equation of second-order apparent kineticsabout DBP degradation was determined as follows:dCDBP/dt=kappCDBP2=1.2317×10-8[O3]0.7413[H2O2]0.8935[pH]1.1069[T]0.8090[GAC]0.3753 CDBP2In view of the kinetic theory of ozone consumption, the diffusion coefficientDO3, the Henry coefficient He and the liquid phase mass transfer coefficient kL,kLa of ozone in DBP oxidation system were determined as6.0010(-100m2/s,11261.28Pa mol/L,2.4010-5m/s and8.8210-4s-1，respectively. The Hattanumber Ha was calculated in the range of0.04to0.1, and the reaction factor Ewas1, which indicated that the catalytical ozonation was in low kinetic regime.The organic pollutants were degraded by competitive oxidations of ozone-directreactions with ozone-indirect reactions, ie. reactions with hydroxyl radicals.Many intermediate products of organics during catalytical ozonation wereidentified by GC-MS using of solid phase extraction. The oxidation pathway of DBP in system was investigated that the DBP was oxidated by series reactions ofisomerization, electrophilic substitution, the hydroxylation and opening ofaromatic rings. Many intermidate compounds were produced and then furtheroxidized by hydroxylation and opening of aromatic rings to short chain aliphaticacids, such as acetic acid, oxalic acid, malonic acid and so on. The aliphatic acidswere finally mineralized completely.The refractory organics existing in biologically treated effluent of antibioticpharmaceutical wastewater were effectively oxidized by composited ozoneheterogeneous catalytical oxidation （O3/GAC/H2O2）. The kinds of organics inwastewater increased first and then decreased during oxidation process. Aromatichydrocarbons and esters were degraded substantially to form by-products of acidanhydrides, carboxylic acids, ketones, phenols, alcohols compounds.Macromolecular organics were oxidized to micromolecular ones during reactions.By the analysis of organic characters at different oxidation status, the evaluationmethodology for organics degradation by ozone catalytical oxidation wasestablished by use of the Mean Oxidation Number of Carbon （MOC）, which wascalculated by COD and TOC indexes. Under the oxidation condition in this study,the more carbon-oxygen bonds were formed in organics, so that the MOC oforganic pollutants was increased from-1.58to-0.13. The biodegradability ofwastewater was improved obviously with the indicator index of BOD5/CODincreasing from0.11to0.78, which was suitable for following stabilizationbiological treatments. |
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