수질과 오염원의 장기적 변화를 통한 팔당호 상수원수질보전 특별대책지역 규제효과 분석

A Study on the Regulatory Effect of the Special Water Preservation Area of Lake Paldang Watershed Based on Long-Term Variation of Pollutant Source and Water Quality

Abstract

The objective of this study was to assess the effect of policies on water quality management based on the changes in pollutants and water quality in Special Water Preservation Area (SWPA) of Lake Paldang watershed from 1990 to 2016. The population, total sewage and flow rate of wastewater in SWPA continuously increased from 1990 to 2016, while the location of new facilities for industrial and livestock facilities has been restricted. However, unlike the buffer zone in which industrial and livestock facilities were continuously reduced after implementing of TMDL, it was found that the effect of land-use regulations on industrial and livestock facilities in SWPA were mitigated by the increase in the size of large facilities. Since 1999 when the emission standard of public sewage treatment plants (STP) was changed, the water quality of Lake Paldang has increased despite the increase of pollutant source. Since emission standard of STP changed in 2012 (BOD 5 mg/L, TP 0.2 mg/L), BOD concentration in Lake Paldang has also improved to the level of water quality in the early 1990s where as TP concentration has remained at its lowest since 1990. BOD and TP average discharge concentration of 43 STP (${\geq}500m^3/day$) in 2016 have been maintained $1.7{\pm}0.7mg/L$ and $0.06{\pm}0.02mg/L$ respectively. While the discharged load of STP in SWPA was decreased by the concentration management, the contribution rate to the total discharged load of non-point pollutants increased to 70 % in 2015, and the contribution rate to the point discharged load of individual treatment facilities increased to 80 %.

Fig. 1. The map showing the special water preservation area and buffer zone of Lake Paldang watershed(☆ Monitoring station, P2).

Fig. 2. The variation of water quality in Lake Paldang from 1990 to 2017.

Fig. 3. The variation of pollutant source in special water preservation area of Lake Paldang watershed from 1990 to 2016 (P, SF, I, IWF, L, LWF, S&WF and TF denotes population, sewage flow rate generated by population, industrial facilities, wastewater flow rate generated by industrial facilities, livestock, wastewater flow rate generated by livestock, sewage and wastewater total generation flow rate and total discharge flow rate in sewage & wastewater treatment plants, respectively).

Fig. 4. Comparison of pollutant source in special water preservation area and buffer zone of Lake Paldang watershed from 1999 to 2016.

Fig. 5. The variation of discharge load in special water preservation area of Lake Paldang watershed from 2010 to 2015.

Fig. 6. The variation of the emission standard and discharge concentration of public sewage treatment plants (≥ 500 m³/day) in special water preservation area of Lake Paldang watershed from 1990 to 2016.

Fig. 7. The variation of water quality in Lake Paldang, and discharge flow rate & load of public sewage treatment plants in special water preservation area of Lake Paldang watershed from 1990 to 2016.

Fig. 8. Comparison of water quality in Lake Paldang during classified three period based on the time when the BOD and TP emission standard of public sewage treatment plants was changed. a, b, A and B indicates significant difference during classified three period.

Fig. 9. Comparison of STP discharged Load, and the ratio of public sewage treatment plants discharged Load to incoming delivery load from Buckhan and Namhan river.

Table 1. Designation status in Special Water Preservation Area and buffer zone of Lake Paldang watershed (2016)