Occurrence of cyanobacteria, actinomycetes, and geosmin in drinking water reservoir in Korea: A case study from an algal bloom in 2012

Abstract

In 2012, a large concentration of geosmin was found in the Paldang reservoir, which is the primary source of drinking water in Seoul, Korea. In June and September 2012, we measured the concentrations of cyanobacteria and actinomycetes, and geosmin, to identify the source of geosmin in the Paldang reservoir. A total of 68 water samples were collected from two sampling sites (Sambong, Paldang), and used to analyze the correlation between cyanobacteria, actinomycetes, and geosmin. The cell density attained a maximum of 24,722 cells/mL on August 11, 2012 and geosmin occurred at a high concentration of 3,934 ng/L on August 13 in Sambong. After July 31, 2012 a rapid increase in growth and cell density occurred with a peak value of 11,568 cells/mL on August 6, 2012. At the same time, the geosmin concentration increased to 3,157 ng/L in Paldang. The number of cyanobacteria positively correlated with geosmin concentration (R2 ¼ 0.84, P < 0.0001), while actinomycetes were not significantly correlated with geosmin (R2 ¼ 0.01, P ¼ 0.709). In addition, the number of actinomycetes was associated with increased turbidity (R ¼ 0.507). Among the various water quality constituents, temperature affected cyanobacteria in the Paldang reservoir (R ¼ 0.803). These results suggest that cyanobacteria are the main source of geosmin in the Paldang reservoir, which might be providing useful information for managing the unpleasant taste of its drinking water.