제주시 한천 저류지의 비점오염물질 특성 및 저감 효과

Abstract

The Jeju Special Self?Governing Province established 11 off?line large scale retention ponds in order to prevent floods after 2007. The reservoirs were mainly designed to prevent floods yet also serve as large scale settling retention ponds that reduce non-point source pollution and help lower the level of pollutants discharged downstream during rainfall by allowing the pollutants to first settle. The study aimed to examine data collected from a field study on four cases of pollutant leaks that occurred in August and September, 2012, in HanCheon Retention pond, which is one of the 11 off?line retention ponds. The result showed the reduction of SS concentration, turbidity, COD, NH3-N, NO3-N, potassium permanganate consumption with 31.7 %, 40.2 %, 80 %, 33.3 %, 25 % and 47 %, respectively, as the outflow of No.1 HanCheon Retention pond flowed to the third section from the first section of the retention pond, indicating that when outflow occurs in the No.1 HanCheon Retention pond, the level of pollutants flowing into the stream can be lowered. Particulate in the retention pond were observed to settle differently depending on several factors such as the location of the retention pond, antecedent precipitation and rainfall intensity; however, they were all immediately settled in the early stage, a phenomenon known as discrete settling. Moreover, the study was conducted in order to calculate pollution load after an inflow into HanCheon1 Retention pond and results showed that BOD, COD, T-N, SS with 266 kg, 4,657 kg, 327 kg, 120,197 kg respectively in 17, September, 2012, and besides in 28, August, 2012 showed that BOD, COD, T-N, SS with 210 kg, 663 kg, 74 kg, 12,037 kg, which means pollution load is proportional to an inflow. In other words, the pollutants being discharged downstream and into the ocean was removed as much as the pollutants being discharged into HanCheon Stream, owing to the retention pond.Because the reduction rate fluctuates depending on the opening and closing of sluices that are installed in the retention pond, further studies upon this matter should be conducted.