Evaluation of an Automatic Drain System of Stagnant Drinking Water: A Case Study of a Water Supply Pipe in Seoul

Abstract

This study provides a case study using an automatic draining solution within the drinking distribution system where it was difficult to maintain an acceptable level of retention time and water quality. Water quality behavior was simulated using EPANET 2.0 in a block system of the distribution network system linked with a given reservoir. The site surveys for the simulated stagnant areas were used for building the automatic drain system at the accessible site. Water quality online monitoring without drain showed that earlier occurrence event of residual chlorine below 0.1 mg/L with 45 days than that of turbidity above 0.5 NTU with 90 days was a critical factor to open and close the drain valve. The discharge volumes of the automatic drain system at the stagnant area were 10~100% of the flushing volume drained by the existing manual drain work. It was confirmed that the volume and cycle of drain could be flexibly changed over time and water temperature. The long term operation of the automatic drain system at the test bed showed that the annual flushing volume and working time could be reduced by 65% and 80%, respectively. The continuous operation of the automatic drain system showed that optimal flushing and online sensing compared to manual drainage could reduce maintenance costs and ensure stable water quality of stagnant drinking water. Although the scope and effect of this study are limited to a particular water pipe, the applicability of an automatic drain system can be evaluated by the approach of this study with optimized drain conditions.