Evaluating the efficacy of pre-oxidation for enhancing removal of HAA5 precursors by conventional drinking water treatment

摘要

The formation potentials of five haloacetic acids (HAA5FP) in 13 surface water samples takennfrom eight cities from northeast to south China were evaluated using the simulated distributionnsystem (SDS) chlorination method. These samples showed a wide range of HAA5FP levels (20 ton443 mg Lu00021). Four pre-oxidation methods were evaluated for their performance in enhancingnHAA5FP removal from six water samples by coagulation. Pre-Cl2 and pre-KMnO4 were notneffective. While pre-ClO2 showed some enhancing effects for all samples, pre-O3 exhibitednmarkedly higher effects without producing perceptible oxidation by-products such as bromate andnformaldehyde. An enhancement factor (EF) value of 13–17% was achieved at an ozone dose ofn0.5 mg Lu00021 and the maximum EF values were 16–25% at an ozone dose of 1.5–2.0 mg O3 Lu00021n(0.3–0.7 mg O3/mg dissolved organic carbon (DOC)). A 3D contour plot was applied toninterpret the effects of two independent variables (DOC and specific ultraviolet absorbancen(SUVA254)) on the formation potential of HAA5 using a quadratic smoothing technique, and itnwas found that the enhancing effect on the removal of HAA5FP by pre-ozonation was attributednto the destruction of reactive sites of organic compound, which could be expressed by thenchanges of SUVA254.