The purpose of this study is to evaluate how discharge water from Daejeon Wastewater treatment plant is affecting the water quality and ecological health of Gap-stream as a point pollutant.
In this study, five points from upstream to downstream of Gap-Stream were selected before and after the inflow of discharge water from the Daejeon Wastewater Treatment Plant (WWTP) to identify the characteristics of water pollution from January 2000 to December 2020. Field surveys of fish for ecological health assessment were conducted twice in June and September 2016.
Analysis of chemical water properties in Not Impacted Site and Impacted Site showed that BOD, COD, TN, TP, EC increased sharply in the Impacted Site. Through this, it is assumed that discharge water from Daejeon Wastewater Treatment Plant causes changes in water quality concentration before and after the inflow of discharge water. It is believed that nutrients nitrogen(N) and phosphorus (P), ions such as sodium ions(Na+) and chloride ions (Cl-), which have been introduced by the discharge water, leading to a sharp rise in total nitrogen (TN), total phosphorus (TP), and electrical conductivity (EC). The distribution of fish in Gap-stream showed that the proportion of Tolerance species and Omnivores increased and the proportion of Sensitive species and Insectivores decreased as the downstream, confirming that the water quality in the downstream was deteriorating. The ecological health level of Gap-stream is average 'normal state(C)'. However, since S3 points are in 'good condition(B)' and S4 points and S5 points are in 'normal condition(C)', It can be said that they have deteriorated near the Impacted Site.
This indicates that the discharge water of Daejeon wastewater treatment plant is a point pollutant source, which accumulates organic matter in Gapcheon and deteriorates the water quality. It suggests that the water quality management of discharged water at Daejeon wastewater treatment plant needs a lot of improvement.