| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系 === 87 === In this study the original sewage system plan of Tam-Shui river basin was re-evaluated and more alternatives were compared. The considered alternatives were compared from both water quality and cost aspects. A QUAL-IIE water quality model was used to evaluate the water quality of the rivers. A gray linear programming approach then was used to obtain optimal sewage plant sites and capacities. This study came out with the following conclusions:
1. From cost aspect, to make sewage plants of upper stream smaller and down stream plants larger usually came out with least cost. However, there are less risk management flexibility and less base flow problems that defeat this kind of planning.
2. The availability of plant site and area are key points in considering alternatives. Regardless of site availability, Hsin-Chun site can be plan to be a large scale plant so that it can be cost effectively used for mediating the sewage from both basin of Da-han River and Hin-Dan River.
3. There is a section in the down stream of Dan-Han River which usually have worst water quality. The only alternative to remedy the problem is to apply third level sewage treatment approach in all sites. However that is not an affordable approach for now.
4. After comparing the considered alternatives, the alternative 8 or the combination alternative is the most cost effective one in spite of its high demand for site area.
5. The gray linear programming results showed that when the design system sewage capacity is between 500 to 900 thousands CMD/yr the cost of the optimal alternative is between 2.52 billion/yr to 4.4 billion/yr.
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