Water Quality Impact Assessment of Future Songdo Sewage Treatment Plant using Korean Water Quality Index

Abstract

Songdo International City has currently developed a waterfront area for an eco-friendly green city, and the waterfront plan includes maintenance of certain water quality level by replacing the water with the inflowing clean seawater in the canal and circulation of the water by bringing in the seawater with the operation of floodgate to be installed outside the canal. This research used the Danish DHI MIKE 3 FM model for the 3D water quality modeling of future Songdo waterfront canal in order to simulate the annual change of water quality with and without Songdo Sewage Treatment Plant and to quantitatively analyze the influence of it through a WQI analysis. Most of canal water comes from the open sea; the canal water quality seems to have similar tendency with the one of open sea; there is considerable quality load due to the effluence of Songdo Sewage Treatment Plant; and the quality change is outstanding in a summer where there is high precipitation.In the result of annual simulation, the water quality evaluation index was relatively high for the southern canal, where the Songdo Sewage Treatment Plant is located, and eastern canal neighboring the outflow gate while the western and northern canals had low index because they are not influenced by the Songdo Sewage Treatment Plant so they would have clean water quality. In a summer, especially, all the canals have bad water quality of rating 4 because of water from the land. Even though the water quality is good for the water from the sea, the water quality of canal can be reduced due to the point and non-point pollution sources, and it will be necessary to make efforts to reduce the pollution load in a summer for the southern and eastern canals under influence of effluence of Songdo Sewage Treatment Plant.