2- Methylisoborneol (2-MIB) is known to cause a musty, moldy taste and odor (T&O) in water. While primarily known for its undesirable effect on the drinking water industry, this compound also causes significant harm in the freshwater fish farming industry. The presence of T&O in potable water supplies is a frequent problem all over the world and in Sri Lanka as well. In some parts of Sri Lanka, the highest consumer complaints are related to the T&O issue even in treated water. Most of the source waters in Sri Lanka consist of diverse ranges of algae and cyanobacteria that produce odorous chemicals; Geosmin and 2- MIB. In the present study, a simple and sensitive modified method to determine 2- MIB in water was optimized by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry. Quantification of 2- MIB concentrations in 30 raw drinking water sources and treated water in both dry and wet seasons was carried out. Results of the study revealed that 69% of both raw and treated water samples exceed the human threshold level of 2-MIB (5 ng L-1) given by the WHO for drinking water. In the wet season, the concentration of 2-MIB in raw water sources ranged from 3.2±1.5 to 57.6±3.1 ng L-1 whereas in the dry season, from 5.8±1.8 to 96.3±4.2 ngL-1. Moreover, in the wet season, 2-MIB concentrations in treated water ranged from 7.6±1.6 to 69.1±1.3 ngL-1 while in the dry season it ranged from 3.5±1.9 to 98.5±2.8 ngL-1. 2-MIB concentrations in treated water were significantly higher (p<0.05) than in the same respective raw water. It was found that the concentrations of 2-MIB were greater in the dry season than in the wet season (p<0.01). In the present study, Anabaena sp., Cylindrospermopsis sp., Oscillatoria sp., Microcystis sp., and algae; Scenedesmus sp., Stauastrum sp., Dictyosphaerium sp., Fragilaria sp. were identified as T&O producing cyanobacteria in water bodies where 2- MIB was detected. Total T&O forming cyanobacteria and algae count has shown a significantly positive correlation with 2-MIB concentration (p < 0.05). A significant positive correlation was found between 2-MIB and total phosphorous (p<0.05) and pH (p<0.05), which are the factors that normally govern cyanobacteria growth and population density in turn will increase the 2-MIB production.
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