Implications of sequential use of UV and ozone for drinking water quality

• Published in: Water research (Oxford) Vol. 40; no. 9; pp. 1864 - 1876
• Main Authors: Meunier, Laurence, Canonica, Silvio, von Gunten, Urs
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2006; Elsevier Science
• Subjects: Applied sciences; Bromate; bromates; Bromates - chemistry; Chlorine Compounds - adverse effects; Chlorine Compounds - chemistry; Cryptosporidium parvum; Disinfection; Drinking water; Exact sciences and technology; irradiation; Micropollutants removal; odor control; Other industrial wastes. Sewage sludge; Oxidants, Photochemical; oxidation; ozonation; Ozone; Ozone - chemistry; Photochemistry; pollutants; Pollution; Seasons; taste; Taste and odor compounds removal; Trihalomethanes - adverse effects; Trihalomethanes - chemistry; ultraviolet radiation; Ultraviolet Rays; UV light; Wastes; Water Purification - methods; Water Supply; water treatment; Water treatment and pollution; France; Europe; Paris; Ile-de-France; France, Paris; Drinking water; Bromate; Ozone; Disinfection; Micropollutants removal; Taste and odor compounds removal; UV light; Discoloration; Microbiology; Ozonization; Cryptosporidium parvum; Pathogenic; Bacteria; Micropollutant; Stream; Oxidation; Biological contamination; Drinking water treatment; Protozoa; Apicomplexa; Parasite; Endocrine disruptor; Ultraviolet radiation; Drinking water treatment plant; Surface water; Metabolic inactivation; Water quality; Phenols; Physicochemical purification; Taste; Odor; Atrazine
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2006.02.030

The formation of bromate levels exceeding the drinking water standard of 10 μg L −1 may impose the reduction of ozone doses used in the treatment of drinking water. This paper illustrates the procedure of evaluating the use of reduced ozone doses while implementing an additional UV disinfection step for an actual drinking water treatment plant. Ozonation was performed at low ozone doses in bench-scale experiments with a pretreated river water from the Paris area (France). At the low ozone dose of 0.5 mg L −1, bromate formation could be kept below 0.4 μg L −1, while inactivation of vegetative bacteria and UV-resistant viruses was calculated to exceed 5 log units, and a substantial decoloration (31% of the absorption at λ = 254 nm ) was achieved. Based on the measured transient ozone and OH radical concentrations, the oxidation of micropollutants was calculated. Fast reacting micropollutants containing phenol, amine or double bond moieties, such as sulfamethoxazole, diclofenac and 17- α-ethinylestradiol, were completely oxidized. Slow-reacting synthetic micropollutants, e.g., atrazine, iopromide and methyl tertiary butyl ether (MTBE), were oxidized by only 20%, 20% and 10%, respectively, and the taste and odor compounds 2-methylisoborneol (MIB) and geosmin by 40% and 50%, respectively. The addition of an UV treatment step to the existing treatment train, which should guarantee disinfection of ozone-resistant pathogenic microorganisms, including Cryptosporidium parvum oocysts, has negligible effects on water matrix components but may induce significant transformation of micropollutants. Overall, the combination of ozonation at reduced doses and UV treatment leads to an improved water quality with regard to disinfection, oxidation of micropollutants and minimization of bromate.