Full scale UV Advanced Oxidation Process with Sodium Hypochlorite for Potable Reuse Treatment – an economic attractive option

Mechanistic and Kinetic Understanding of the UV254 Photolysis of Chlorine and Bromine Species in Water and Formation of Oxyhalides

“…The combination of chlorine with UV has recently gained attention as an advanced oxidation process (UV/chlorine AOP) in which hydroxyl radicals ( • OH) and reactive halogen species are formed from the photolysis of chlorine. , UV/chlorine AOP is applied to eliminate recalcitrant organic contaminants in drinking water treatment and wastewater reclamation for water reuse. − The impact of bromine (Br – ) on the UV/chlorine AOP is of high interest because Br – is ubiquitous in fresh water and present at concentrations ranging from 10 to 2000 μg L –1 . − Bromine is formed in situ during the chlorination (or ozonation) of Br – -containing waters, especially saline waters, − following eq . Furthermore, UV/bromine might be directly relevant to saline/brackish water treatment by chlorine (or ozone and peracetic acid) followed by UV for the oxidative treatment of saltwater swimming pools, ocean ship ballast waters, and ocean aquaculture waters. ,− Chlorine and bromine in the current study refer to freely available chlorine (HOCl and OCl – ) and bromine (HOBr and OBr – ) species, respectively. …”

Transformation of an Amine Moiety of Atenolol during Water Treatment with Chlorine/UV: Reaction Kinetics, Products, and Mechanisms

“…Chlorination followed by UV is relevant for drinking water treatment as chlorine (referring here to free available chlorine, HOCl/OCl – ) is used for a preoxidation process before coagulation and filtration processes. , In this sequential use of chlorine and UV, chlorinated waters are subjected to UV photolysis in the presence or absence of residual chlorine. Combined use of chlorine and UV has been proposed as an advanced oxidation process (commonly denoted as UV/chlorine AOP) , and intensively tested in bench-scale studies − and also occasionally in pilot- and full-scale studies. , The performance of UV/chlorine as an AOP is superior or comparable to that of UV/H 2 O 2 at acidic and neutral pH but lower at basic pH, due to the pH-dependent hydroxyl radical ( • OH) oxidation efficiency. , Elucidating the major reactive species responsible for organic contaminant degradation in UV/chlorine has been the subject of investigations, since UV photolysis of chlorine produces a range of radical species, such as • OH, chlorine radicals ( • Cl), dichlorine radicals (Cl 2 •– ), and oxychlorine radicals (ClO • ) as described in reactions – . It has been found that • OH was the main oxidant for recalcitrant contaminants with electron-deficient substituents, while • Cl, Cl 2 •– , and ClO • (termed as reactive chlorine species, RCS) become important for the degradation of contaminants with electron-rich moieties. , …”

“…Combined use of chlorine and UV has been proposed as an advanced oxidation process (commonly denoted as UV/ chlorine AOP) 11,12 and intensively tested in bench-scale studies 13−22 and also occasionally in pilot-and full-scale studies. 23,24 The performance of UV/chlorine as an AOP is superior or comparable to that of UV/H 2 O 2 at acidic and neutral pH but lower at basic pH, due to the pH-dependent hydroxyl radical ( • OH) oxidation efficiency. 13,25 Elucidating the major reactive species responsible for organic contaminant degradation in UV/chlorine has been the subject of investigations, since UV photolysis of chlorine produces a range of radical species, such as • OH, chlorine radicals ( • Cl), dichlorine radicals (Cl 2…”

“…photolysis in the presence or absence of residual chlorine. Combined use of chlorine and UV has been proposed as an advanced oxidation process (commonly denoted as UV/ chlorine AOP)11,12 and intensively tested in bench-scale studies13−22 and also occasionally in pilot-and full-scale studies 23,24. The performance of UV/chlorine as an AOP is superior or comparable to that of UV/H 2 O 2 at acidic and neutral pH but lower at basic pH, due to the pH-dependent hydroxyl radical ( • OH) oxidation efficiency 13,25.…”