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Characterization of nom in water and the effects of ozonation on the nom and chlorinated DBPs Chowdhury, Farah Laj

Abstract

The objective of the present study was to evaluate the effect of the characteristics of natural organic matter (NOM) constituents on disinfection by-product (DBP) formation, and to examine the effect of ozonation on the NOM constituents that form DBPs. A characterization technique was developed to better understand the type of NOM present in drinking water sources before and after ozonation. The characterization technique was applied to water taken from two raw water sources: the Capilano reservoir and the Thompson River. The NOM in these water sources was fractionated based on sizes [less than 1 KDa (LT1 KDa), less than 5 KDa (LT5 KDa), and less than 10 KDa (LT10 KDa)]. Each size fraction and the original unfractionated stream was then further fractionated into different polar fractions (i.e. hydrophobic, transphilic, and hydrophilic). The Capilano reservoir water was composed of 27% NOM smaller than 1 KDa and 73% greater than 1 KDa. For the Thompson River water, almost 95% of the NOM was smaller than 1 KDa and less than 5% of the NOM was greater than 1 KDa. Most of the NOM is hydrophilic in nature for the Capilano reservoir water, and transphilic in nature for the Thompson River water. For the Capilano reservoir water, 15% of the total haloacetic acid formation potential (HAAFP) and 12% of the total trihalomethane formation potential (THMFP) was generated by the NOM components that were smaller than 1 KDa, and the remaining of the total disinfection by-product formation potential (DBPFP) was generated by NOM components that were larger than 1 KDa. For the Thompson River water, 82% of the total HAAFP was generated by NOM components that were smaller than 1 KDa, and the remaining of the total HAAFP was generated by NOM components that were larger than 1 KDa. For the Thompson River water, the THMFP was all essentially generated by NOM smaller than 1 KDa. For the Capilano reservoir water transphilic fraction NOM had a higher DBPFP than the hydrophobic or hydrophilic NOM fractions. For the Thompson River water, no consistent trend was observed between the formation of DBPs and the NOM present in the different polar fractions. Total organic carbon (TOC) concentration of the water did not change as a result of ozonation, but the composition of NOM changed during ozone treatment that was demonstrated by the reduction in specific ultraviolet absorbance (SUVA). No consistent relationship was observed between the reduction in SUVA for the different size and polar fractions and the reduction in the DBPFP. Ozonation was very effective in reducing DBPFP for larger NOM component (>10 KDa) than smaller NOM component (

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