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

The formation potentials of five haloacetic acids (HAA₅FP) in 13 surface water samples taken from eight cities from northeast to south China were evaluated using the simulated distribution system (SDS) chlorination method. These samples showed a wide range of HAA₅FP levels (20 to 443 μg L⁻¹). Four pre-oxidation methods were evaluated for their performance in enhancing HAA₅FP removal from six water samples by coagulation. Pre-Cl₂ and pre-KMnO₄ were not effective. While pre-ClO₂ showed some enhancing effects for all samples, pre-O₃ exhibited markedly higher effects without producing perceptible oxidation by-products such as bromate and formaldehyde. An enhancement factor (EF) value of 13–17% was achieved at an ozone dose of 0.5 mg L⁻¹ and the maximum EF values were 16–25% at an ozone dose of 1.5–2.0 mg O₃ L⁻¹ (0.3–0.7 mg O₃/mg dissolved organic carbon (DOC)). A 3D contour plot was applied to interpret the effects of two independent variables (DOC and specific ultraviolet absorbance (SUVA₂₅₄)) on the formation potential of HAA₅ using a quadratic smoothing technique, and it was found that the enhancing effect on the removal of HAA₅FP by pre-ozonation was attributed to the destruction of reactive sites of organic compound, which could be expressed by the changes of SUVA₂₅₄.