Oxidation of odorous and nonodorous algal metabolites by permanganate, chlorine, and chlorine dioxide

The six algal metabolites, at concentrations of 20-225 μg/l, were oxidized with potassium permanganate, chlorine, or chlorine dioxide at doses of 0.25-3 mg/l. Flavor profile analysis (FPA) was used to determine the odors of the solutions before and after oxidation. Linoleic and palmitic acids, which are odorless compounds, were oxidized to odorous products by all three oxidants. The odor intensity of β-cyclocitral (grape, sweet tobacco) and phenethyl alcohol (rose, floral) was only slightly decreased by any of the oxidants. Oxidation by permanganate or chlorine either eliminated or greatly reduced the odors associated with linolenic acid (watermelon) and 2t,6c-nonadienal (cucumber); chlorine dioxide was ineffective at reducing the cucumber odor of 2t,6c-nonadienal. Oxidation, at doses typically applied for drinking water treatment, can result in the destruction of certain algae-related odors but in the formation of other odors.