高科技產業用水回收率指標之研究

Abstract

水資源匱乏問題日益嚴重，政府於1995年度起，為減緩新水源開發之壓力，並確保國家整體水資源供給不虞匱乏，陸續推動了「節約用水措施」，更於2000年「節約用水行動方案」中提出，應進行用水成效查核法案之研擬與推動，使節約用水提升至法治管理的層面，達到依法管水、節水的目標。目前工業用水考核指標中，以製程回收率及全廠回收率之利用最為廣泛，然而全廠回收率計算公式依主管機關卻有所差異，且計算結果差異甚大，但整合出之回收率計算公式，在全廠回收率標準值未能配合修正前，恐無法達成既定政策及環保要求，故至今仍維持現狀，保留其彈性空間。 本研究旨在探討全廠回收率計算公式，使其更符合節水精神且更具通用性，研究成果：1.全廠回收率計算公式（R1）中加計冷卻水塔循環水後，以50家科技廠用水回收狀況分析，所得出全廠回收率值均高於94﹪以上，故研判（R1）公式無法分辨高科技廠商回收率之好壞。2.全廠回收率計算公式（R3）在原設計時，因考量冷卻水塔蒸發溢散量為不可避免且無法回收之項目，故將其扣除，但由本研究之探討發現，冷卻水塔蒸發溢散量可藉由節水措施，降低補充水量，故R3公式扣除次級用水蒸發量，不符合節水精神。3.全廠回收率（R3）計算公式之C5及C6，為空調及廢棄洗滌塔系統中經處理設備處理後之循環水量，經本研究重新定義，應以能降低系統排放之水量多寡為加計原則。4.本研究將使用低耗能省水設備時，所節省之「省水量」納入回收計算。5.整合出全廠回收率（R4）計算公式，並分析當全廠回收率計算公式，改採本研究提出之（R4）或（R2）公式計算時，全廠回收率標準值依製程用水量、蒸發量與總用水量比值差異（產業特性不同），建議標準值下修6.6﹪~17﹪。6.依實際、特殊、極端情形及無製程用水等案例，分析各回收率計算公式在不同狀況下，回收率標準值達成率、鑑別性及通用性等優劣情形。 關鍵詞：工業用水考核指標、製程回收率、全廠回收率、冷卻水塔循環水、冷卻水塔蒸發溢散量、經處理設備處理後之循環水量、省水量、鑑別性。

Shortage of water resources has turned out to be a crucial problem worldwide. To release problems of water resources exploration and to ensure an abundant water supply, the government has launched a series of water saving measures since 1995 and set up a number of water saving acts and water use efficiency checking regulations in 2000, in an eye to carry out water saving and water use management by mean of laws and regulations. As for industrial water use checking index, application is found widely on recycle rate of manufacturing process and overall fab recycle rate. However, formula for overall fab recycle rate varies in different authorities, which in turn results in different calculation results. Before amendment of the overall fab recycle rate, the integrated recycle rate formula can hardly meet demands of existent policies and environmental protection related regulations. Thus, the conventional system keeps in use before any amendments. This study aims at figuring out the formula for overall fab water recycle rate, so as to solidify water saving efficiency for wide application. Conclusions and results reached in this study include: 1. Formula for overall fab water recycle rate (R1) counted on a database of 50 tenant companies at the Hsinchu Science Park, which cooling tower circulating water was taken into account, revealed that the overall fab recycle rate is over 94%, indicating that the formula R1 can hardly detect the efficiency of overall fab water recycle rates. The formula for overall fab recycle rate (R3), which deducted the water vaporized in the cooling tower and listed the vaporized water as secondary water use that can not be recycled, doesn’t not follow the water saving guidelines since the vaporized water can be reduced by mean of water saving measures, where deduction of vaporized water is not appropriate. 3. Formula C5 and C6 for overall fab recycle rate (R3) originally depicts the circulating water for air-conditioners and waste gas scrubber systems, which is redefined as the discharged water that can be saved in the systems. 4. Saved water for water saving devices is taken into water recycle account. 5. Standard value for overall fab water recycle rate (R4) is down revised 6.6% to 17% after figuring and analyzing the overall fab water recycle formulas and counting the manufacturing process water use, vaporized water, and the total water use differences for varied industries by mean of adopting the formula (R4) and (R2) proposed in this study. 6. Recycle standard rate accomplished, approaches for differentiation, and application feasibilities are analyzed after taking a number of practices, unique cases, extreme cases, and no water use manufacturing processes into account and figuring out a number of recycle formulas under different circumstances.

Key words: industrial water use reference checking index, manufacturing water recycle rate, overall fab water recycle rate, circulating water for cooling tower, vaporized water in cooling tower, circulating water after treatment by equipment, water saving amount, and approaches for differentiation.