集水區消毒副產物前質流佈之探討

Abstract

原水經自來水場消毒處理後會形成不同類別的消毒副產物，一些研究顯示其毒性可能造成膀胱癌以及生殖危害。天然有機物與氯反應後所形成之消毒副產物中，最廣為檢驗及研究者包含三鹵甲烷、鹵乙酸、鹵乙腈以及亞硝胺，然而仍有將近百分之七十的消毒副產物尚未被發現。 天然有機物係由溶解性及粒狀有機物所組成，一般被視為是消毒副產物之主要前質，其來源可分為植物性或是生物性，例如落葉、降雨、沿岸基質、濕地及水體本身有機物。雖然飲用水中之消毒副產物的控制可由水場本身透過淨水工程操作加以控制，近來有關水源水質的控管以及集水區管理被廣泛討論、亦被視為較有效率的環境管理辦法。 本研究之目的在探討集水區中天然有機質及人為汙染如何影響水源水質及水中消毒副產物生成。研究選取台灣金門、基隆、台北三個區域之集水區與水源區進行水中消毒副產物前質之探討，並搭配地理資訊系統(GIS)進行土地使用比例的計算，以期找出集水區土地使用與水源水質及消毒副產物前質間之關係。 研究結果顯示，台北集水區因有良好的管理機制、天然有機物的量相較之下較低。含氮溶解性有機物在基隆有較高濃度、在金門則是碳類有機物濃度較高。經地理資訊系統所運算出之土地利用類型及比例，經與水質參數進行統計分析後，結果顯示人為相關之土地使用是影響基隆原水中有機物濃度的主因，而農業的土地使用密度則是影響金門水質的正相關因子。

Disinfection byproducts (DBPs) are groups of chemicals formed from reactions between disinfectants and natural organic matters (NOM). Several categories of DBPs have been regulated due to their potential connections with bladder cancer and reproductive effects. Among different categories of DBPs, trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and nitrosamines are four major groups of known DBPs frequently detected in drinking water, while 70% of DBPs still remain unknown. Regarded as the primary precursors of DBP formations, NOM is a combination of dissolved and particulate organics originated from plants and animals. Its sources can be discovered in five different ways: fallen leaves, rainfall, littoral zones, wetlands and water body. Despite the fact that controls of DBPs in drinking water can be achieved with alternative technologies, among which reduction of DBP precursors from raw water is the most effective way. Since the NOM and anthropogenic pollution in watersheds have been shown to be the major sources of DBP precursors in several studies, this study attempts to correlate the land use and DBPs precursors in three Taiwanese watersheds (Taipei, Keelung and Kinmen) to assess the sources of the DBP precursors. Water samples from the three watersheds were collected and corresponding water quality characteristics were analyzed. Combined with land use information in watersheds, the results were used to elucidate the correlations between the watershed land use, the source water qualities, and the following DBPs formation after chlorination. The results showed that Taipei watershed has the lowest NOM level because of the best watershed management, the highest concentration of nitrogen organic matter occurred in Keelung watershed, while the Kinmen watershed had the highest carbon organic matter level. ArcGIS was used to access the land use proportions in the three watersheds, the results demonstrated that the anthropogenic land uses may cause the raise of the dissolved organic matter in Keelung watershed, while the high natural organic matters in Kinmen watershed resulted from the agriculture activities. It is recommended that more monitoring activities should be done to verify the relationships between land use and source water qualities.