Abstract
Lake Biwa, the raw water source of the Osaka municipal water works, has been suffered from the musty odor occurrence for the past seven years. The causative compounds have been identified 2-methylisoborneol (2-MIB) and geosmin. The maximum concentration of 2-MIB and geosmin detected so far at the outlet of lake Biwa was 313ng/l and 620ng/l respectively. The threshold odor concentration of 2-MIB and geosmin in drinking water was determined 4ng/l and 100ng/l respectively, according to the triangular taste and odor testing methods. These compounds in raw water colud not be removed efficiently by the conventional water treatment processes even with an addition of powdered activated carbon. Ozonation coupled with granular activated carbon filtration could remove them by almost 100%.
