Chun Gyeong Yoon

Feasibility study of ecological wastewater treatment system for decentralized rural community in South Korea

AbstractThe natural and ecological wastewater treatment system (NEWS) was developed to target organic pollutants and nutrients for decentralized rural communities. The system was installed in Sangwang-dong, Gongju-si, Chungcheongnam-do, South Korea, and operated for about nine months. It consisted of three parts: the anaerobic septic tank, the absorbent-biofilter system (ABS), and the up- and down-flow constructed wetland. The respective nitrogen (N), phosphorus (P), and chemical oxygen demand removal rates of the NEWS were 45.94, 48.65, and 98.47% in the growing season and 27.93, 23.78, and 86.45% in the winter season. The significantly low N and P removal rates could have been caused by microorganism vitality in the ABS, as most of the nutrients occurred in an organic form. Average water temperature of the ABS was 18.13°C in the growing season and 8.289°C in the winter season, which might have influenced the low overall removal rate during the winter season. Performance of the NEWS was efficient, indepe...

Modification of SWAT model for simulation of organic matter in Korean watersheds.

The focus of water quality modeling of Korean streams needs to be shifted from dissolved oxygen to algae or organic matter. In particular, the structure of water quality models should be modified to simulate the biochemical oxygen demand (BOD), which is a key factor in calculating total maximum daily loads (TMDLs) in Korea, using 5-day BOD determined in the laboratory (Bottle BOD(5)). Considering the limitations in simulating organic matter under domestic conditions, we attempted to model total organic carbon (TOC) as well as BOD by using a watershed model. For this purpose, the Soil and Water Assessment Tool (SWAT) model was modified and extended to achieve better correspondence between the measured and simulated BOD and TOC concentrations. For simulated BOD in the period 2004-2008, the Nash-Sutcliffe model efficiency coefficient increased from a value of -2.54 to 0.61. Another indicator of organic matter, namely, the simulated TOC concentration showed that the modified SWAT adequately reflected the observed values. The improved model can be used to predict organic matter and hence, may be a potential decision-making tool for TMDLs. However, it needs further testing for longer simulation periods and other catchments.