In the past, if we emphasized sanitary water mainly on disinfection treatment due to concerns about waterborne infectious diseases, paradigm has recently been transformed into tasty and healthy water as well as safe water with enhanced water quality standards.
Therefore, government and Water service providers restriving to minimize the concentration of residual chlorine by strengthening the residual chlorine management system during the water purification plant and supply process.
K-water aims to produce and supply clean tap water with less chlorine odor by implementing the residual chlorine equalization project in keeping with the needs of the citizens who want safe and healthy drinking of tap water.
In order to maintain and equalize the residual chlorine concentration in the supply process, the residual chlorine in the water treatment plant is supplied to 0.8 mg/L or less.
The re-chlorine injection facility is installed and operated in the process of sending and receiving to supplement the shortage of residual chlorine. Also, the residual chlorine concentration at the inlet of the reservoir is maintained at 0.4 mg/L or more so that the residual chlorine concentration of 0.1 mg/L or more can be secured in the water intake.
The residual chlorine equalization project in the supply process maintains the proper concentration in time and space constantly without a rapid descent or rise according to the season and transfer distance from the water purification plant to the tap water reservoir, thereby reducing the chlorine odor and improving the tap water drinking rate and disinfection by-And to improve the water quality management process in the supply process.
In this study, we introduced and operated a method of dispersing and injecting re-chlorine by operating two re-chlorine injection facilities on the water pipeline in order to equalize the residual chlorine in the entire water pipe and to ensure the proper concentration of residual chlorine in the reservoir.
This study was conducted to investigate the level of equalization of residual chlorine concentration during tap water supply process and to investigate whether proper residual chlorine is ensured to the reservoir and whether water quality improvement such as change of disinfection by - product concentration is effective.
As a result of this operation, it was adjusted down to 0.8 mg/L lower than 1.0 mg/L which is the upper limit of residual chlorine in the water treatment plant by dispersing and injecting the chlorine in the supply process, and the existing chlorine was lowered by 0.12 mg/L The installed chlorine remained operating throughout the year to maintain the appropriate residual chlorine in the endpoint reservoir.
The variation of residual chlorine concentration was 0.24~0.77 mg/L before the improvement, 0.53 mg/L was the variation width and 0.29~0.61 mg/L after the improvement. The fluctuation range was 0.32 mg/L, which was lowered to 40 % to reduce chlorine odor.
The residual chlorine equalization width was improved to 2 times in winter, 1.9 times in spring and 1.5 times in summer, and the average residual chlorine equalization width was improved 1.8 times. After the improvement of THM concentration, water treatment plants decreased 15 % on the average and 2.9~10.7 % on the supply side. HAA decreased 16.9 %, 16.8 %, and 31.3 %, respectively.
The amount of liquid chlorine used and the unit cost of water treatment plants were reduced by 15 % by 0.29 won/㎥ after the improvement, and the amount of disinfectant used was increased by replenishing the remaining chlorine with the chlorine in the supply process. However, the use of total disinfectant was reduced by 0.07 won/㎥, which was 4 %.