Recent trends in off-flavor problems were investigated by a nationwide questionnaire survey targeting 239 drinking water treatment plants (DWTPs) maintained by 79 regional water suppliers (RWS) in Japan. The results indicated that 43 of 79 (54%) RWS and 89 of 239 (36%) DWTPs were affected by off-flavor problems in a recent 2-year period (October 2010–September 2012). Off-flavor incidents occurred in all regions in Japan. Most DWTPs affected by off-flavor incidents take in water from closed water areas, such as dams and lakes, where phototrophic microorganisms, such as cyanobacteria and algae, can grow easily. The most common off-flavor was an earthy–musty odor, while a fishy smell was also reported in some cases. The common producers of geosmin were Anabaena spp., while those responsible for 2-methylisoborneol were Phormidium spp. and Oscillatoria spp. The off-flavor events frequently occurred during summer and early fall months (June–September). The water temperature and pH of raw water for the production of drinking water when off-flavor problems occurred were higher than those during normal periods. To eliminate off-flavor compounds, most DWTPs (about 58%) adopt powdered activated carbon treatment, which considerably increases operational costs.
Nationwide survey of organism-related off-flavor problems in Japanese drinking water treatment plants (2010–2012)
Naohiro Kishida, Masaki Sagehashi, Hirokazu Takanashi, Naoshi Fujimoto, Michihiro Akiba; Nationwide survey of organism-related off-flavor problems in Japanese drinking water treatment plants (2010–2012). Journal of Water Supply: Research and Technology-Aqua 11 November 2015; 64 (7): 832–838. doi: https://doi.org/10.2166/aqua.2014.171
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