污水處理廠與礫間設施效益之評析-以大台北地區為例

Abstract

大台北地區目前均已建置10餘座的污水廠及現地處理設施，雖污水接管普及率及整體污水處理率亦較其他地區超前，惟在未完成全面的用戶接管前，家戶的污水仍排入側溝內，進而影響河川水質，目前仍藉由現地處理設施淨化水質，可有效提昇污水妥善處理率外，併兼具營造河岸生態棲地與生物多樣性等附帶效益，且以就地排放方式，挹注河川流量，提昇河川承受污染的緩衝能力。 為評估污水廠及現地處理設施的興建營運是否妥適，本研究彙集大台北地區2座污水處理廠與2處礫間處理設施的相關興建與營運成本及100年至101年兩年度水質監測資料。運用淨現值法及益本比法在相同基準年下比較其成本與效益，進而計算各廠(場)址益本比以探討操作是否具經濟效益，並輔以問卷調查了解民眾心中對污水廠及礫間設施的觀感及需求。 研究結果顯示，排除因天災影響致進流量下降的礫間場址，另1/2處礫間處理設施的益本比大於1，其餘2座污水廠取其平均的益本比亦在1以上，皆為有效率且投資良好的民生污水處理方案。現今教育普及化及政府大力推行污水處理政策宣導下，有9成以上民眾均能接受都市生活污水需經過處理，且超過5成的民眾都能認同污水廠的污染物去除率比礫間設施好、污水處理量比較多及污水單位處理成本會比較高，與本研究中污水廠的去除率與處理量及單位水量處理操作成本分析數據結果相符；對污水廠的接受度和整體效益的認同亦高於礫間處理設施，可知民眾對污水處理的認知已不同於以往，日後污水處理設施在民眾心中將是打造水質淨化且舒適親民的環境，而不再是人人避而遠之的鄰避設施了。

The Greater Taipei city has nowadays 10 wastewater treatment plants and 13 gravel contact oxidation treatment facilities in total. Its sanitary sewer system and sewage treatment coverage rate is much higher than that in other regions of Taiwan. Despite above-mentioned advantages, before the household piping is fully connected, the household sewage still needs to be directly discharged into the ditch sides, which aggravates the water quality of the rivers. Using on-site river water treatment facility to purify the water can effectively improve the sewage treatment rate, foster riverside habitat biodiversity, increase river basal flow rate and enhance rivers’ buffering capacity against pollution. To evaluate the cost effectiveness of wastewater treatment plants and on-site water treatment facilities, this research first collected the construction and operation costs of two wastewater treatment plants and two gravel contact oxidation treatment facilities in Greater Taipei city and also collected their water monitoring data in 2011~ 2012. Then the Net Present Value (NPV) and Benefit/Cost (B/C) ratio methods has been used to understand the relationship between cost and benefits in the same year so as to know if the operation is economically-beneficial. A public survey was also conducted to collect the civilians’ opinions and expectations for the installation of wastewater treatment plants and gravel contact oxidation treatment facilities. This research revealed that excluding the force-majeure that could negatively affect the inflow rate of the gravel contact oxidation treatment facilities, one of the 2 gravel contact oxidation treatment facilities had greater than 1 B/C ratio. Also the B/C ratio of the both wastewater treatment plants was higher than 1. The investment in household sewage treatment indeed had positive returns. With the popularization of education and governmental promotion of sewage treatment policy, up to 90% of the interviewees agreed that the city’s sewage needs to be properly processed, and over 50% recognized that wastewater treatment is better than gravel contact oxidation treatment in terms of pollutant removal rate, sewage treatment capacity, and sewage treatment unit cost, which coincided with the cost analysis result of this research. The public also expressed higher acceptance and recognition over wastewater treatment plants than gravel contact oxidation treatment facilities. This state that the public attitude toward the sewage treatment has changed overtime, its just not a water purification unit but also something which helps to create a more comfortable environment .