| 英文摘要 |
The project “The water quality detail designing project for Nyo-tzo river and Ba-Zan river in Cha-yi city” finished at Dec. 31st, 2005. This project is divided into four parts, which are described as followed,
A. The investigation and analysis of river background information
According to the Nyo-tzo river (Pu-Zi river water basin) water quality analysis done by Taiwan EPA and our bureau, we found that at the main river branch, wastewater was discharged near Lu-San bridge inspection station by some stock breeding farmers. Besides Hua-sing bridge station, all the water quality qualified rates for the other three stations turned out to be zero. As for the water quality of the end session of Nyo-tzo river bridge, due to the enormous amount of wastewater discharged from Ming-shun sewage system (industrial wastewater and household wastewater), three major sewage systems in Cha-yi city, residential household wastewater and the industrial wastewater from Ho-Hu industrial park, the main Nyo-tzo river branch flows through Cha-yi city is seriously polluted.
The RPI values for Ba-Zan river water quality near Guen-hue bridge and Jung-Yi bridge are 2.75 and 3.75 respectively; these values are much lower than the average RPI value of the year 2004. In the future, if the water quality improvement project is completed, the pollution level can be further reduced. However, the BOD level near Jung-Yi bridge is elevated; this is due to the more frequent inspections at the months of February and March. It can also be attributed to the wastewater discharged near the bridge, and also the lower water level due to the dry season. After April, the pollutant concentrations lowered due to the higher amount of rain. As a whole, the water pollution is not very serious, therefore, more precaution should be taken to prevent the worsen of water quality.
B. Pollution sources investigation and analysis
For the investigation of pollution sources, 4 spots were found by Ba-Zan river basin, another 4 spots by Nyo-tzo river basin; they all have been cleaned up. There are 8 water discharging channels by Ba-Zan river basin; among them, the one near Jung-Yi bridge has highest water flow (up to 5,000 CMD), by far the biggest pollution source in this area. As for Nyo-tzo river basin, there are 21 main water discharging channels; Ming-shun sewage system has the highest water flow (around 8,000CMD).
During the holidays and non-holidays, continuous 24-hr water sampling (mixed samples, samples being taken every two hours) has been performed at 2 water discharging channels near Ba-Zan river basin and 5 spots near Nyo-tzo river basin. Water flow measurements were also done (measurements were taken every two hours). The results showed that the average BOD concentrations is the highest near Jung-Yi bridge (BOD value is as high as 140 mg/L); average concentrations of total –Chromiun and Cr6+ have the highest values at Ho-Hu water channel.
C. Estimation of the amount of pollution and water quality models
The amount of BOD, NH3-N and TN being produced is estimated to be 11,568.8 kg/day for BOD (household wastewater takes up higher percentage, around 94.3%), 407.9 kg/day for NH3-N (household wastewater also takes up higher percentage, around 88.7%), and 694.9 kg/day for TN (household wastewater takes up around 86.8%).
In addition, the water quality data, water flow data and annual water quality data of both Nyo-tzo river basin and Ba-Zan river basin have been compiled to establish a suitable water models. How values of BOD, NH3-N and DO fluctuate within the river basins can be estimate precisely by using the models.
D. Designing and enforcement of water clarification project
This project mains to improve the water quality near Guen-hue bridge (Ba-Zan river basin) and to reduce the pollution from seriously polluted to moderately-polluted. An investigation has been done regarding one major pollution source near Jung-Yi bridge (upper Ba-Zan river basin) that has water flow of 5,000 CMD and the water is seriously polluted. This has great effect on the test stations near Jung-Yi bridge and Guen-hue bridge. San-Yi pulp-and-paper factory has been found to produce the highest amount of wastewater (water flow up to 675 CMD). Water clarification system has been planned to clean up the water body in between Guen-hue bridge (Ba-Zan river basin) and Jung-Yi bridge.
Cha-Yi county EPA also has the intention to start a water clarification project near Jung-Yi bridge. Therefore, the Taiwan EPA utilized one big water pipe for connecting tow locations into one big system. The upper river in charged by Cha-Yi county EPA has serious water pollution problem, therefore, a stone-treatment system is utilized. 5,000CMD of wastewater is pumped to be treated. The treated clean water is then shipped to a designated location near the lower river. Since the water quality is improved after being treated, it is finally polished by using an artificial wetland.
The water treatment process for our wetland system follows the steps,
1. the wastewater discharged thorough Jung-Yi bridge water channel is treated by the stone-treatment system of Cha-Yi county EPA.
2. The water goes through a pipe into the final natural clarification system.
3. The total processes: bush wetland, swamp wetland, immersion bed, pipe, ecosystem lake, and finally, water meter. The treated water is recycled for the irrigation of the whole park, and the extra water goes back to Ba-Zan river basin.
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