TiO_2/UV/O_3-BAC processes for removing refractory and hazardous pollutants in raw water

摘要

TiO_2/UV/O_3-BAC (biological activated carbon) process was employed to treat raw water and compared to UV/O_3-BAC process in its optimum parameters (3 mg/L ozone dosage with 15 min oxidation time and 15 min empty bed contact time in BAC). The results showed that the presence of TiO_2 improved ozone utilization and biodegradability of the effluent. For the dissolved organic carbon (DOC) removal, TiO_2/UV/O_3-BAC was more efficient than UV/O_3-BAC and its synergetic effect is more than that in UV/O_3-BAC process. It was showed that small molecules with MW < 3000 Da predominated in the raw water accounting for more than 56% DOC, they were increased after oxidation, accounting for more than 64% DOC. GC/MS analysis showed that TiO_2/UV/O_3-BAC process was effective in removing phthalate esters (PAEs) and persistent organic pollutants (POPs). PAEs' removal ratio reached more than 94% and reduced with the increase of the length of the alkyl side chains and the alkyl branch chains. TiO_2/UV/O_3-BAC process was also very effective in removing POPs. Polybromobiphenyls' removal rate reached more than 89% and decreased with the increase of substitutional bromines except for 2,2',5,5'-tetrabromobiphenyl, which can be completely removed.