Analysis of Disinfection By-products Occurrence at Water Treatment Plants in Daegu and Gyeongsangbuk-do, Korea from 2011 to 2024

The water treatment plant is a key facility to remove pathogenic microorganisms in order to supply safe tap water to the people, and due to its efficiency, economy, and persistence, a disinfection process using chlorine-based disinfectants is widely used. However, chlorine-based disinfectants react with organic substances during the chlorine disinfection process to produce disinfection by-products that are harmful to the human body, and these substances are strictly managed internationally. The Nakdong River basin has a characteristic that the concentration of disinfection by-products is higher than that of other watersheds due to high contamination load and enhanced chlorine treatment. Therefore, in this study, 91 water treatment plants in the Daegu and Gyeongbuk region were classified according to water supply and analyzed the generated concentration of disinfection by-products (THMs, HAAs, and HANs). Using the data from the national water supply information system, changes by year and month were identified, and the difference in the occurrence of disinfection by-products was compared according to whether or not an advanced treatment process was introduced. In addition, based on the data from the Meteorological Administration, the correlation between temperature and the concentration of disinfection by-products was evaluated through the Pearson correlation coefficient. As a result of the analysis of water treatment plants in Daegu and Gyeongbuk from 2011 to 2024, THMs, HAAs, and HANs all showed high concentrations in water treatment plants using river water and lake water as raw water, and were relatively low in groundwater and riverbed water. THMs showed a positive correlation with rising temperature (r = 0.4357), whereas HANs exhibited no correlation. HAAs tended to show increased variability and higher median values with increasing temperature, but no statistically significant correlation was observed. In addition, it was confirmed that the concentration of all disinfection by-products was lower in the water treatment plant that introduced the advanced water treatment process compared to the standard water treatment process. For safe supply of tap water, it is essential to comply with the appropriate concentration of disinfectant injection by seasonal, and in order to effectively remove precursors that may generate disinfectant by-products depending on the water source, it is effective to introduce advanced treatment processes such as ozone and activated carbon.