Abstract
Trichloroacetic acid (TCAA) is a disinfection byproduct from the chlorination of natural organic matter. Because the Japanese drinking water quality standard of TCAA was revised to be 0.03 mg/L in 2015, the disinfection byproducts including TCAA were required to be controlled more severely in the water treatment process. The maximum concentration of TCAA in the tap water in Kyoto was 0.019 mg/L sampled on November in 2013, when the raphidophyte was observed in the raw water for the first time. The trend of TCAA concentration in the tap water showed the similar trend of the raphidophyte occurrence in the raw water. This study investigated the chlorination of the unialgal strain of the raphidophyte. As the result, TCAA formation was increased with increasing the cell number of the raphidophyte. In conclusion, the raphidophyte was found to be the main precursor of TCAA increased in the tap water in Kyoto on November in 2013. The pre-chlorination was stopped in the water treatment plants in Kyoto at the raphidophyte occurrence in the raw water.
