C.-M. Kao*, K.-F. Chen, Y.-L. Liao and C.-W. Chen Institute of Environmental Engineering, National Sun Yat-Sen University, Chinese Taiwan (E-mail:
[email protected]) Abstract The Kaoping River basin is the largest and the most intensively used river basin in Taiwan. It is 171 km long and drains a catchment of more than 3,250 km2. Based on the current water quality analysis, the Kaoping River is heavily polluted. Concern about the deteriorating condition of the river led the Government of Taiwan to amend the relevant legislation and strengthen the enforcement of the discharge regulations to effectively manage the river and control the pollution. Investigation results demonstrate that both point and non-point source pollutants are now the causes of biochemical oxygen demand (BOD), nutrients, and pathogens in the river. The main water pollution sources are livestock wastewater from hog farms, municipal wastewater, industrial wastewater, non-point source (NPS) pollutants from agricultural areas, and leachate from riverbank landfills. The current daily BOD, NH3-N, and TP loadings to Kaoping River are 74,700, 39,400, and 5,100 kg, respectively. However, the calculated BOD, NH3-N, and TP carrying capacities are 27,700, 4,200, and 600 kg per day. To protect public health and improve the river water quality, a comprehensive management and construction strategy is proposed. The proposed strategy includes the following measures to meet the calculated river carrying capacity: (1) a hog ban in the entire Kaoping River basin, (2) sewer system construction to achieve 30% of connection in the basin within 10 years, (3) removal of 10 riverbank landfills, and (4) enforcement of the industrial wastewater discharge standards. After the implementation of the proposed measures, the water quality should be significantly improved and the BOD and nutrient loadings can be reduced to below the calculated carrying capacities. Keywords BOD; carrying capacity; hog farm waste; riverbank landfill; water quality
Water Science and Technology Vol 47 No 9 pp 209–216 © IWA Publishing 2003
Water quality management in the Kaoping River watershed, Taiwan
Introduction
The Kaoping River basin is the largest and the most intensively used river basin in Taiwan. It is 171 km long, drains a catchment of more than 3,250 km2, and has a mean flow of 239 m3/s. The average precipitation is 2,000 mm/yr. Figure 1 shows the Kaoping River, its catchment, and three major reaches (Chi-San Creek, I-Lio Creek, and Lao-Non Creek). It serves as a water supply to the Kaohsiung City (the second largest city in Taiwan), several towns, two counties, and a number of large industries (electronic, steel, petrochemical, etc.). In the meantime, it also receives their treated and untreated wastewater. Taiwan Environmental Protection Administration (TEPA) has developed a three-part classification system (Classes A, B, and C) for Kaoping River based on the purpose of water usage and degree of protection for each stream section (TEPA, 1998). Table 1 presents the water quality criteria for the three classes in Kaoping River. Basically, the upstream is classified as Class A, mid-stream is Class B, and the downstream near the outfall is Class C. Thus, the highest degree of protection is given to Class A. Recent water quality analysis by EPA indicates that the Kaoping River is heavily polluted (Ning et al., 1998; TEPA, 1999). The concentrations of some major water quality indicators [e.g. biochemical oxygen demand (BOD), suspended solid (SS), ammonia-nitrogen (NH3-N), total phosphorus (TP), and Escherichia Coliform (E. coli)] are much higher than the Kaoping River water quality criteria. Because of the occurrence of steep slopes in part of the Kaoping River flow courses, the higher dissolved oxygen (DO) level is usually observed due to the natural turbulence in
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C.-M. Kao et al. Figure 1 Kaoping River basin and three major reaches
the river, which enhances the mass transfer of oxygen between the river and atmosphere (natural reaeration). Because of the poor raw water quality, the cost for water treatment has been significantly increased by the Taiwan Water Supply Company in the Kaoping region. However, the quality of drinking water is still questioned and complained about. Concern about the deteriorating conditions of the Kaoping River led the Government of Taiwan to amend the relevant legislation and strengthen the enforcement of the discharge regulations to effectively manage the river and control the pollution. The Government also requests the Taiwan Water Supply Company to apply an advanced water treatment system to provide high quality drinking water to the people in the Kaoping River basin. The major objectives of this study were to (1) review the recent information on water usage and assess the water quality, (2) identify the current contributions of point and non-point source pollutants to the river pollution, (3) select an appropriate water quality model for water quality simulation and carrying capacity calculation, and (4) develop river management protocols to improve the river and raw water quality. Point and non-point source pollution
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Results from the review of recent information on the water usage and investigation of the water quality demonstrate that both point and non-point source (NPS) pollutants are now the causes of BOD, nutrients, and pathogens in the river. The main water pollution sources are livestock wastewater from hog farms, municipal wastewater, industrial wastewater, NPS pollutants from agricultural areas, and leachate from riverbank landfills. In the Kaoping River basin, most of the upper catchment is used for agricultural activities including cropland and livestock farming. In the upper catchment, NPS pollutants mainly associated with stormwater runoff from agricultural land uses can be quite diffuse and
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difficult to treat. Nutrients, pesticides, and sediments are the main detrimental NPS constituents. Investigation results show that the NPS pollution contributes more than 10% of the overall pollution loads to Kaoping River (CTC, 1999). Hog farming is a particularly important activity in the rural area in the basin. The total hog population is estimated to be more than one million in the whole catchment, and approximately half of the population is in the lower catchment (downstream of the Da-Shu Dam). Most of the untreated hog farm waste is indiscriminately discharged into the river. Thus, the hog farm waste and agricultural runoff from the cropland are two major causes of the deterioration of Kaoping River water quality. Currently, the overall percentage of public sewer system (for collection and disposal of municipal wastewater) connection in Taiwan is only 7%. Due to the rapid urban and industrial expansion, the percent of sewer system connection in the Kaoping River basin is less than 5%. Most of the municipal wastewater in the basin (especially in the rural area) is discharged into the river without treatment. Moreover, there are 229 registered industrial factories that discharge their wastewater into the Kaoping River. However, illegal or expedient discharges are sometimes practised feeding polluted industrial flows into the river. Therefore, the untreated municipal and industrial wastewaters are also two causes of the poor water quality. In the Kaoping River basin, due to the shortage of available lands for landfill construction, some townships used the riverbank sites as the domestic garbage dumping locations or converted them to simple landfills. Those riverbank landfills (or garbage dump sites) were neither well designed nor well maintained. Thus, landfill leachate could significantly deteriorate the downstream river water quality. There are 10 abandoned riverbank landfills within the Kaoping River floodplain. Leachates from those 10 landfills are currently polluting Kaoping River and might also cause the clogging problems during the flood season. Water quality modeling
In this study, the Enhanced Stream Water Quality Model (QUAL2E) was selected as a water quality-planning tool to perform the water quality evaluation and carrying capacity calculation (Brown and Barnwell, 1987). The QUAL2E Windows interface was developed by the U.S. Environmental Protection Agency to assist the implementation of the Total Maximum Daily Load (TMDL) program. It can simulate up to 15 water quality constituents including BOD, nutrients, DO, temperature, algae as chlorophyll A, and coliforms. It uses a finitedifference solution of the advective-dispersive mass transport and reaction equations. A stream reach is divided into a number of computational elements, and for each computational element, a hydrologic balance in terms of stream flow, a heat balance in terms of temperature, and a material balance in terms of concentration are written. Both advective and dispersive transport processes are considered in the material balance. Mass is gained or lost from the computational element by transport processes, wastewater discharges, and withdrawals. Mass can also be gained or lost by internal processes such as release of mass from benthal sources or biological transformations. Hydraulically, QUAL2E is limited to the simulation of time periods during which both the stream flow in river basins and input waste loads are essentially constant. QUAL2E can operate as either a steady-state or a quasidynamic model, making it a very helpful water quality planning tool. When operated as a steady-state model, it can be used to study the impact of waste loads (magnitude, quality, and location) on instream water quality. By operating the model dynamically, the user can study the effects of diurnal variations in meteorological data on water quality (primarily dissolved oxygen and temperature) and also can study diurnal dissolved oxygen variations due to algal growth and respiration. However, the effects of dynamic forcing functions, such as headwater flows or point loads, cannot be modeled in QUAL2E.
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Previous studies have been performed to obtain the input data for the QUAL2E model construction (Ning et al., 1998; TEPA, 1999; CTC, 1999). The input data include stream segmentation, locations of inflow and outflow, geological and meteorological conditions, hydrological parameters, decay rates, water quality parameters, dispersion coefficient, reaeration coefficient, BOD removal rate, and benthal oxygen demand. After the model construction, the recent water quality data were used for model calibration (Ning et al., 1998; Chiang et al., 2000). Figure 2 presents the measured and simulated water quality results for DO, BOD, NH3-N, and TP in the Kaoping River from the mouth (0 km) to the 84 km upstream location. Results demonstrate that the simulated data had a good match with the analytical water quality results. Based on the investigation, the current daily BOD, NH3-N, and TP loadings to Kaoping River are 74,700, 39,400, and 5,100 kg, respectively. Results indicate that the hog farm wastes generated from one million hogs contribute 37,900 kg BOD per day, which is more than half of the daily BOD loads to the river. The untreated municipal wastewater also contributes more than 25% of the daily BOD loading. 15 criteria DO
10
analytical results
mg/ C
5
0
0
A
B
20 40 60 80 Distance from the river mouth, km
simulated data
100
15 criteria BO
10
ana lytical results
D
simulated data 5
C B A
0
0
20 40 60 80 Distance from the river mouth, km
100
15 criteria NH
10
analytical results
3-N simulated data mg/
5
0
C 0
B A 20 40 60 80 Distance from the river mouth, km
100
15 criteria TP
10
analytical results simulated data
mg/ 5 B A 0
212
0
20 40 60 80 Distance from the river mouth, km
100
Figure 2 Measured and simulated water quality results (DO, BOD, NH3-N, and TP) and three water quality classes (Classes A, B, and C) from the outfall (0 km) to the 84 km upstream location
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Significant effects of the riverbank landfills on water quality were also observed. Results reveal that landfill leachate contributes 5,000 kg per day of the BOD loading (close to 7% of the daily loads) into the river. Because E. coli appears to be the most representative of fecal contamination in the water contamination, the colony forming unit (CFU) of E. coli is also used as the indicator of water quality in Taiwan (Table 1). Figure 3 presents the measured and simulated E. coli concentrations (CFU/100 mL) in the Kaoping River from the mouth (0 km) to the 84 km upstream location. Results also show that the simulated data had a good match with the analytical results. Results show that the most possible causes of the high E. coli measurements at some locations are the hog farm wastes and domestic wastewater discharges. Model confirmation using decreased hog population in 1997
The hog population dropped to 0.8 million in the whole Kaoping River Basin due to the foot-and-mouth disease in 1997. Thus, the discrepancy of the water quality results between the years of 1996 and 1998 reveals the decreased impacts of hog wastes on water quality before and after the foot-and-mouth disease, respectively. The 1998 water quality data were used for QUAL2E model confirmation. Figures 2a to 2c present the measured (1996 and 1998 data) and simulated 1998 water quality results for BOD, NH3-N, and TP in the Kaoping River from the river mouth to the 84 km upstream location, respectively. Results demonstrate that the simulated 1998 results matched with the analytical water quality results. The analytical results show that the manure from hog farming caused the significant increases in BOD and NH3-N concentrations (Figures 2a and 2b). The unchanged TP concentrations indicate that hog wastes had limited contributions on TP loadings to the Kaoping River. Carrying capacity calculation
The carrying capacity calculations for BOD, NH3-N, and TP were performed using the calibrated QUAL2E water quality model to obtain the maximum acceptable BOD, NH3-N, Table 1 Allowable water quality criteria in Kaoping River Category A1
Category B
Category C
most upstream reach1
most midstream reach1
downstream reach1
> = 6.5 1 0.1 10 0.02 = 5.5 2 0.3 –2 0.05 = 4.5 4 0.3 – – 4,200 (carrying capacity)
Table 2c Simulated TP loading to Kaoping River after the implementation of each proposed plan Scenario
1 2 3 4 5 6 7 214
Measure
Hog ban in the upper catchment (upstream of Da-Shu Dam) to reduce half of the hog population Hog ban in the whole basin Sewer system construction (achieve 20% of connection in 5 years) Sewer system construction (achieve 30% of connection in 10 years) Removal of riverbank landfills Enforcement of the industrial wastewater discharge standards Scenarios 2 + 4 + 5
Reduced TP loading
Remaining TP loading
(kg/day)
(kg/day)
500
4,600
2,800 –
2,300 –
–
–
80 –
5,020 –
3,600
1,500 > 600 (carrying capacity)
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is located at the upstream location of the Da-Shu Dam, Scenario 1 is to impose the hog ban in the upper catchment (upstream of the Da-Shu Dam). Due to the wide spreading of the hog farms in the upper catchment, only 6,000, 1,500, and 500 kg of the daily BOD, NH3-N, and TP loadings could be reduced. Results demonstrate that the following measures are required to reduce the daily BOD, NH3-N, and TP loads to below the calculated carrying capacity: (1) a hog ban in the whole Kaoping River basin, (2) sewer system construction to achieve 30% of connection in the basin within 10 years, (3) removal of 10 riverbank landfills, and (4) enforcement of the industrial wastewater discharge standards. Results indicate that approximately 48,000 kg of daily BOD loading can be reduced, and the remaining BOD loading (26,700 mg/day) is lower than the 27,700 mg per day BOD carrying capacity after the implementation of four river management measures. However, NH3-N, and TP loads are still far beyond the calculated carrying capacities (Tables 2b and 2c). Conclusions
The water quality of the Kaoping River, particularly that of its downstream reach, has deteriorated markedly over the past 10 years. This has largely been due to (1) substantial increase of the hog population in the basin, (2) untreated municipal and industrial wastewater discharges due to urban and industrial expansion, (3) intensified agricultural development in the upper catchment, and (4) riverbank garbage dumpings. Both point and non-point source pollutants are the major causes of the poor water quality. Thus, improvements of conventional wastewater collection and treatment, as well as reductions in the contaminant loads from point and non-point sources are required to improve the river water quality. A comprehensive strategy for Kaoping River basin management has been proposed. The strategy consists of short-term management and improvement measures (e.g. 10 riverbank landfills removal), long-term structural measures (e.g. sewer system construction), and land use management and legislation (e.g. hog ban and enforcement of wastewater discharge standards). After the implementation of the proposed measures, the water quality can be significantly improved and the BOD loading can be reduced to below the Kaoping River carrying capacity. To provide high quality drinking water, two other issues have been addressed: (1) establishment of appropriate river and raw water quality criteria for the Kaoping River, and (2) application of the advanced water treatment technology for raw water treatment. Progress in these and other related areas would be essential if the challenges to river water management and water quality improvements are to be met. Acknowledgements
This study was funded by National Science Council in Taiwan. Additional thanks to Prof. Chang N.B., Prof. Wen C.K., and Mr. Ning, S.K. of National Cheng-Kung University, Prof. Kuo J.T. of National Taiwan University, and Prof. Yu S.L. of University of Virginia for their support and assistance throughout this project. References Brown, L.C. and Barnwell, T.O. (1987). The Enhanced Stream Water Quality Models QUAL2E and QUAL2E-UNCAS: Documentation and User Manual. Report EPA/600/3-87/007, U.S. EPA, Athens, GA, USA. Chiang, P.C., Kao, C.M., Lin, T.F. and Yan, Y.L. (2000). Sustainable Taiwan 2011. Taiwan National Science Council, Taipei, Taiwan. CPA, Construction and Planning Administration (2001). Study on Quantitative Criteria of Affecting Factors, Delineation Guidelines, and Performance Indicators for Delineating the Source Water Protection Area of Water Quality and Quantity for Water Supply, Taipei, Taiwan. CTC, China Technical Consultants, Inc. (1999). Drinking Water Protection Plan in Kaoping River, Report to Kaohsiung County Environmental Protection Agency. Kaohsiung County, Taiwan.
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CTC, China Technical Consultants, Inc. (2000). Drinking Water Protection Plan in Ping-Tung County, Report to Ping-Tung County Environmental Protection Agency. Ping-Tung County, Taiwan. Ning, S.K., Shu, S.Y., Chiang, C.L., Yang, L. and Chang, N.B. (1998). Water quality analysis in Kaoping River basin, The 11th Environmental Planning and Management Conference. Tainan, Taiwan, pp. 216–223. TEPA, Taiwan Environmental Protection Administration (1998). Water Pollution Act, Taipei, Taiwan. TEPA, Taiwan Environmental Protection Administration (1999). Industrial Wastewater Management Strategy (I). EPA-88-U1G1-03-117, Taipei, Taiwan. TEPA, Taiwan Environmental Protection Administration (2000). Industrial Wastewater Management Strategy (II). EPA-89-U1G1-03-002, Taipei, Taiwan. TEPA, Taiwan Environmental Protection Administration (2001). Investigation of Non-point Source Pollution in the Drinking Water source Water Protection Area of Kaoping River Basin. EPA-90-G10302-223, Taipei, Taiwan.
