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Assimilable organic carbon formation during ultraviolet-hydrogen peroxide advanced oxidation treatment of surface water Bazri, Mohammad Mahdi

Abstract

Practice of UV/H₂O₂ advanced oxidation treatment has emerged as viable alternative for removing micro-pollutants and other organic contaminants from surface water. However, presence of natural organic matter (NOM) in water is problematic and hinders the efficacy of the treatment process. Indeed, NOM can undergo significant partial oxidation leading to generation of smaller more easily assimilable organic molecules (i.e., AOC). Earlier studies have found AOC as the potential cause of bacterial regrowth and other water health concerns thereof within the distribution system. Nonetheless, impact of UV/H₂O₂ process on biostability of downstream water has not gained much attention. However, a method recently developed by Hammes and Egli (2005) opened the opportunity for more accurate and relatively rapid quantification of the AOC. The main focus of this research was to modify and evaluate the protocol of Hammes and Egli (2005) for quantifying the biostability of water before and after UV/H₂O₂ process. More importantly, this research aimed to contribute substantially to the current understanding of easily assimilable organic molecules formation during UV/H₂O₂ treatment. As a result, different characterization techniques (e.g., HPSEC, UV₂₅₄, and TOC) were utilized to monitor transformation of NOM and to study the relationships among different NOM characteristics (e.g., molecular size distribution, UV₂₅₄, and AOC). Considering the concerns associated with NOM (especially when oxidation is applied in the treatment train), elimination of NOM ahead of the oxidation process can potentially increase the UV/H₂O₂ treatment efficacy as well as the finished water quality. Moreover, as the regulations become more stringent, many utilities hope to comply with them by retrofitting existing facilities and avoiding the construction of new ones. Thus, this research also focused to investigate the impact of a pre-treatment process such as coagulation to eliminate NOM prior to UV/H₂O₂ treatment. Using coagulation as pretreatment ahead of UV/H₂O₂ will be potentially of interest for those utilities that are currently applying coagulation and hope to comply with new regulations by minimum capital investment. More importantly, this would be beneficial because of the need to improve process efficacy and also final water quality and the reduced formation of disinfection by-products (DBPs) within the distribution system.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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