Research On The Removal Of Trace Organic Pollutants In Taihu Lake By Advanced Oxidation Processes And Biological Pretreatment

Typicalendocrine disrupting chemicals, pharmaceuticals and personal care products were detected in Taihu Lake raw water for the past few years. These compounds cause great potential threat to human health and can not be removed effectivity by conventional water treatment processes. The micro-polluted source water in Taihu Lake were taken as the research object in this paper. On the foundation of survey and analysis to trace organic pollutants in raw water, study of ozone and biological pretreatment were carried out to remove trace organic pollutants, together with long pipeline reactor. The results may provide a reference for practical production. The following results were obtained:(1)39 kinds of volatile and semivolatile organic pollutants were detected in Taihu Lake. The major pollutants were PAEs. The maximum concentration of dimethyl phthalate (DMP) and Dibutyl phthalate (DBP) were 0.63?g/L and 0.49?g/L, respectively.(2)Ozonation can reduce sulfa antibiotics and PAEs effectively. The degradation of the two kinds of contaminants by ozone mainly rely on direct oxidation of O3 molecules. Increasing the initial concentration of target contaminants would worsen the degradation efficiency while increase in the ozone dose and contact time can both improve the degradation of organic pollutants. When the reaction time was 40min, the dosage of ozone achieved 3mg/L and 4mg/L, the removal rates of SMX and SM2 were 98.7% and 96.5% respectively in the coupling preprocessing of ozone and biological pretreatment,while ozonation contributed 83% and 79.3%. When the concentration of ozone was 3mg/L and the reaction time was 30min, the coupling preprocessing removed DMP and DBP at the rates of 83.3% and 95.7%.(3)The analysis of the intermediate products suggested that the degradation pathway of PAEs may be the side-chain structure of PAEs were attacked with the scission of C-C or C=O bond. PAEs were transformed to small molecule organics, intermediatephthalic acid and finally broke up into CO2 and H2O. The change of toxicity during the degradation was investigated. The results showed that the intermediate products of sulfa antibiotics have stronger biological toxicity than original matters. Estrogenic activity was reduced with the removal of DBP, but the intermediate products of DBP also presented estrogenic activity. DBP and its intermediate products were reduced continuely in the biological process, with estrogenic activity being removed almostly completely.(4)When the concentration of ozone was 3mg/L and the reaction time was 30min, the total removal rates of CODMn, UV254 and DOC in the processes of ozonation, biological pretreatment, coagulating sedimentation, sand filter and GAC filter were 81.3%,87.8% and 67.0% respectively, increasing 36.1%,57.2% and 34.9% than no preprocessing.(5) The addition of K.2FeO4accelerated the removal of target pollutants in long pipeline reactor. However, the ability to wipe out pollutants of per unit mass declined when the dosage of K2FeO4 increaed. When the dosage of ozone was 1mg/L, the dosage of K2FeO4was 20mg/L, ozonation, biological pretreatment coupling with long pipeline reactor removed SMX, SM2, DMP and DBP at the rates of 70.6%,53.3%,89.7% and 83.2%, respectively.