Ozonation parameter for removal of oestrogenicity from secondary effluent without by-products

The purposes of this study are to investigate ozonation characteristics, to evaluate oestrogenicity and to confirm behaviours of by-products during ozonation of secondary effluent. For the ozonation of secondary effluent, TOC was decreased only 10% when 4 (mgO₃/mgC) of ozone consumption per initial TOC. However, UV₂₅₄ and SUVA was decreased approximately 65% until ozone consumption of 2 (mgO₃/mgC). Ozonation was also shown to be very effective for decrease of oestrogenicity in secondary effluent. Bromate ion started to form obviously when the ozone consumption per initial TOC exceeded 2 (mgO₃/mgC) and increased while the time of ozonation became longer. From these results, ozone consumption per initial TOC was shown to be an appropriate operation parameter to reduce SUVA effectively and E₂ equivalent concentration to less than 0.1 nM without significant formation of bromate ion, and its value was determined to be 2 (mgO₃/mgC) in ozonation of secondary effluent.