Levels of Two Earthy and Musty Odor Compounds, 2-Methylisoborneol and Geosmin, in Wastewater and Concentration Variations during Treatment

Abstract

We determined the concentrations of 2-methylisoborneol (2-MIB) and geosmin in final effluent from wastewater treatment plants in Kyoto City, Japan, investigating variations during treatment. The concentrations of 2-MIB and geosmin in final effluent were 5.1–29.8 and 3.9–13.9 ng/L, respectively. Geosmin concentrations in primary effluent were higher than those in influent. The concentration of 2-MIB increased in the reactors, while that of geosmin decreased. The anaerobic-anoxic-oxic and step-feed biological nitrogen removal processes lowered 2-MIB and geosmin concentrations more than did the anaerobic-oxic activated sludge process. Other factors regulating the concentrations of earthy and musty odor compounds may include activated sludge flowing from the secondary settling tank, changes in total nitrogen removal efficiency, anaerobic conditions in reactors or secondary settling tanks, and deterioration of activated sludge, including by formation of a scum layer.