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Issue 4, 2016
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Emerging investigators series: the efficacy of chlorine photolysis as an advanced oxidation process for drinking water treatment

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Abstract

The photolysis of hypochlorous acid (HOCl) and hypochlorite (OCl) produces a suite of reactive oxidants, including hydroxyl radical (˙OH), chlorine radical (Cl˙), and ozone (O3). Therefore, the addition of light to chlorine disinfection units could effectively convert existing drinking water treatment systems into advanced oxidation processes. This review critically examines existing studies on chlorine photolysis as a water treatment process. After describing the fundamental chemistry of chlorine photolysis, we evaluate the ability of chlorine photolysis to transform model probe compounds, target organic contaminants, and chlorine-resistant microorganisms. The efficacy of chlorine photolysis to produce reactive oxidants is dependent on solution and irradiation conditions (e.g., pH and irradiation wavelengths). For example, lower pH values result in higher steady-state concentrations of ˙OH and Cl˙, resulting in enhanced contaminant removal. We also present the current state of knowledge on the alteration of dissolved organic matter and subsequent formation of disinfection by-products (DBPs) during chlorine photolysis. Although the relative yields of DBPs during chlorine photolysis are also dependent on solution conditions (e.g., higher organic DBP yields at low pH values), there is conflicting evidence on whether chlorine photolysis increases or decreases DBP production compared to thermal reactions between chlorine and dissolved organic matter in the dark. We conclude the review by identifying knowledge gaps in the current body of literature.

Graphical abstract: Emerging investigators series: the efficacy of chlorine photolysis as an advanced oxidation process for drinking water treatment

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Publication details

The article was received on 28 Jan 2016, accepted on 17 May 2016 and first published on 17 May 2016


Article type: Critical Review
DOI: 10.1039/C6EW00029K
Citation: Environ. Sci.: Water Res. Technol., 2016,2, 565-579
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    Emerging investigators series: the efficacy of chlorine photolysis as an advanced oxidation process for drinking water treatment

    C. K. Remucal and D. Manley, Environ. Sci.: Water Res. Technol., 2016, 2, 565
    DOI: 10.1039/C6EW00029K

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