製程廢水回收處理系統之經濟效益研究

Abstract

科學工業園區管理局為促進與輔導園區內廠商有效利用水資源，降低缺水壓力避免對工廠生產造成影響損失，特訂定嚴格的用水回收率標準。本研究中個案工廠因水回收率法令的要求下，必需進行提升用水回收率的工程投資。評估中的「製程切割研磨廢水回收系統擴充」及「製程低濃度氟酸廢排水回收工程」之投資預算是經多家水處理專業工程承商報價彙整後所擬定，在系統正式運轉後是否能有水回收效益，是必須執行經濟效益評估的。 本研究首先調查個案工廠現況的全廠用水成本，為評估水回收案建立基礎資料。再分別評估水回收工程案設置後對全廠用水成本的影響，並以工程經濟分析工具之淨現值法（Net Present Worth，NPW）對這水回收工程與現況進行經濟效益評估。為避免過於樂觀的評估，造成誤判，故最後再以這兩個水回收系統依投資金額及回收系統產水效率的變異進行敏感性分析。 結果發現，預估投資「製程切割研磨廢水回收系統擴充」 每年全廠用水成本（含設備折舊）為26,020,650 元，「製程低濃度氟酸廢排水回收工程」每年全廠用水成本（含設備折舊）為26,341,955 元。與個案工廠現況每年全廠用水成本為26,510,713 元相比較，似乎是符合經濟效益。 但經淨現值及敏感性分析後，「製程切割研磨廢水回收系統擴充」在投資金額比預算金額多139%時，仍然符合經濟效益的；若回收系統產水效率在低於49.7%以下時，將不符合經濟效益。「製程低濃度氟酸廢排水回收工程」若以預算金額進行投資，與現況比較是不能符合經濟效益，除非投資金額比預算金額低7%；而產水效率部分，若能提高到71.7%以上時，即可符合經濟效益。此研究結果，可以提供個案工廠在執行工程議價及未來系統操作時參考。

The high standard of water reuse ratio has been setting up for Science Park Administration to avoid the losses on the production of the vendors’ factories inside the Science Park through the promotion and supervision them the effectively usage of water resources and the reduction the water crisis.

In this study case, it is regarding to the project investments for a factory to build two engineering projects which upgrades the water recovery rate to meet the law of standard of water reuse ration. Those two projects are DSR/BG Waste Water Reclaim System and LHF Waste Water Reclaim System. It is necessary to have the Assessment of economic benefits of the Effectiveness of water reclaim for those two projects basic on the quotations from the engineering contractors.

First of all, the data base for the study of the water reuse ratio has been collected basic upon the total water use cost of current factory. Secondary, the Assessment of economic benefits before and after the projects has been evaluated by the Net Present Worth, NPW, a tool of the Engineering Economy. In order to have the ultimate evaluation without any misjudgment, a Sensitivity Analysis has been processed by the variation of investment and reclaim efficiency from these two water reclamation projects.

From the result, the costs of applying DSR/BG Waste Water Reclaim System and LHF Waste Water Reclaim System (including Equipment depreciation) per year are $ 26,020,650 NTD and $ 26,341,955 NTD. It seems to be a positive results of the economic benefits compared to the current cost of $ 26,510,713 per year without applying one of these systems. After the analysis of the Net Present Worth and the Sensitivity Analysis, the results are different. For the DSR/BG Waste Water Reclaim System, it is positive to the economic benefits when the percentage of the investment is under 139% and the effectiveness of water reclaim is higher than 49.7%. For the LHF Waste Water Reclaim System, it is negative to the economic benefits unless the percentage of the investment is lower than 7% and the effectiveness of water reclaim is higher than 71.7%. The results provide the reference to the future engineering bargaining of the project assessment for the factory.