高速公路服務區水資源再利用及效益評估研究

Abstract

依據經濟部水利署預計台灣地區截至2021年總需水量將為200億m3/年，但目前各種水資源可供之水量約180億m3/年，在未來的十餘年間，將缺少20億m3/年。台灣雨量充沛，但因地形陡峻，河川短促，無法有效留住雨水，80%的雨水大都逕流入海，剩下的20%如何有效利用值得重視；另一方面，截至民國94年底，按內政部營建署之統計，台灣地區營運中、規劃及施工中之都市污水處理廠至今應已有百座以上之規模，且絕大部份均符合現行放流水水質標準，故將來都市污水處理廠之放流水必然成為一穩定而寶貴之新興水源，而雨水貯留及再生水推廣勢必成為政府的重點工作。目前台灣地區國道第一、三、五號高速公路共設置十四處服務區，各服務區公共設施完善，均設有污水處理廠，且在各企業主努力經營下至今已各具凡特色，除原有暫時停留休息功能外，已然成為各地的觀光景點。其中清水服務區因位於國道三號之中點，鄰近大台中都會區，又有國道四號由國道三號聯繫至國道一號，停靠、休息、用餐旅客亦特別多，故選擇台灣中部之清水服務區為研究樣區，經調查及蒐集相關資料進行再生水效益評估研究。 本研究針對現有污水廠處理設施、增添再生處理設備及增加雨水貯留等情況分別作效益評估：1.以樣區現有RBC二級污水處理廠放流水，及經既有設施再生處理後，回收250CMD再生水作澆灌之用-效益評估結果，再生水成本6.43元/m3，自來水水價為11.5元，實質經濟效益每年可節省自來水費463003元，如以全部高速公路14處服務區計算，每年可節省自來水費6,482,042元。2.增加回收再生水為600CMD，除作澆灌利用外並擴大利用於廁所沖洗，但須增加廁所沖洗專用之再生水管路及設備-效益評估結果，再生水成本大幅降低為3.75元/m3，自來水水價11.5元，實質經濟效益為每年節省水費1,697,250元。如以全部高速公路14處服務區計算，每年可節省水費23,761,500元。3.雨水貯留220 CMD，須增加設備-每年可節省自來水費每年節省之費用為149650元，並且可達機動調配供水之功效。 目前台灣高速公路服務區共計有14處，如均能採取污水回收或雨水貯留再利用，並利用區內導覽設施廣為宣傳，則必能引起帶頭作用，使我國雨水貯留及再生水利用能儘速推展，進而達到水資源永續經營之目標。

According to the report of the Water Resources Agency (水利署), the demand of water resources in Taiwan is 20 billion m3/year and current supply only reaches 18 billion m3/year. The need of 2 billion m3/year is a big challenge for government. Moreover, owing to steep geographical features, river make 70% runoff into ocean and only 16% is stored. Consequently, water recycling and water reuse would be the primary development. The discharge of wastewater treatment plant and rainfall storage (中水) have great potential. The treated wastewater which meets the EPA requirements and the “clean” rainfall could meet certain water use. The purpose of this research was to evaluate the efficiency of water reuse in the highway service area. At present, there are totally fourteen zones of the highways in Taiwan. Among them, Ching-sheui service area was selected as the research site to study the existing runoff system, water supply, biological wastewater treatment plant, sewage/sewer disposal system and irrigation system. The method was to recycle water resources from rain water and to reuse the effluent of wastewater treated. Further treatments were completed to meet the requirements of reclamation water, then, the water can be used to flush toilets, irrigate plants, clean roads, fill courtyard pools, etc. Finally, this research was focused on the cost and benefit analysis of whole system in the area. We setup 4 scenarios to analyze cost benefit ratio: (1) Discharge Water for Irrigation Only: we tried to utilize currently available facilities. In this case, 250 CMD water could be saved for irrigation. Current tap water is NT$ 11.15 per m3, the system reuse could reduce the water prices to NT$ 6.43 per m3 and the annual saving will be up to NT 0.5 million. (2) Discharge Water for Irrigation and Toilet Flush: for this purpose, we needed to increase reused water of 600 CMD and to build up the distribution system with the facilities of toilets cleaning. The results showed the binary water supply system will save up to NT$ 1.6 million annually with water price of NT$ 3.75 per m3. (3) Discharge Water for Both Irrigation and Toilet Flush to Meet Future Reclamation Standard: in order to raise the water quality to meet the standard in the future and to keep the same 600 CMD reused water. This case could save NT$ 1.2 million per year. (4) Further Storage of Rainfall 220 CMD: this case could save NT$ 0.1 million per year to make the system more reliable and flexible. This study evaluated the feasibility of binary water supply system in Ching-sheui service area to promote and develop a practical nationwide project for water reclamation and to guide the direction of sustainable water use.