全氟化合物於工業汙水處理廠及其下游河川之穩定性與流佈調查

Abstract

全氟化合物(PFCs)為持久性環境化合物，廣泛應用於各種工業上，因而普遍分佈於自然環境中。本研究利用臭氧程序(臭氧濃度: 16 mg/L)和臭氧結合過氧化氫程序(過氧化氫濃度: 0.033 mM)無法使perfluorooctanoic acid (PFOA)和perfluorooctane sulfonate (PFOS)達到去除效果。即使結合加壓臭氧程序(包含三種不同加壓程序及加入過氧化氫)仍無法使之分解。因全氟化合物如此穩定之特性，使之易流佈於汙水處理廠中。故針對兩處台北市汙水處理廠、新竹工業科學園區汙水處理廠及其下游河川進行分析，偵測到十種全氟化合物，其中包含perfluoroalkyl sulfonates (PFASs: PFBS, PFHxS and PFOS)及 perfluoroalkyl carboxylates (PFCAs: PFHxA, PFHpA, PFOA , PFNA, PFDA, PFUA and PFDoA)。此十種全氟化合物中，PFOS (濃度高達293 ng/L)及PFHxA(濃度高達293 ng/L)為市立汙水處理廠之主要汙染物。然而工業汙水處理廠以及其下游河川中主要之汙染物為PFHxS(濃度高達2406.7 ng/L)、PFOS(濃度高達6050 ng/L)和PFOA(濃度高達517.3 ng/L)。其顯示全氟化合物以及組成之濃度，於市立汙水處理廠及工業汙水處理廠間有很大的差異，此差異可能由於汙染源不同所造成。此外，在工業汙水處理廠及其下游河川之土壤中可檢測到PFOA(濃度高達2 ng/g)、PFUA(濃度高達4.1 ng/g)和PFDoA(濃度高達15.8 ng/g)。而比較土壤及河水中濃度比例(ng/kg/ng/L)分別為PFOA：4、PFUA：766及PFDoA：6088，因此發現較長碳鏈之PFCAs較容易受土壤吸附。因此大多數之PFUA和PFDoA在自然環境中係存在於土壤中，而PFOA則存在於水體中。

Perfluorinated compounds (PFCs) are persistent environmental contaminants and are widely used in many industries. Many researchers reported that PFCs distributed in the environment. This study demonstrated that perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were stable during ozonation (16 mg O3/L ) and ozonation combined with H2O2 (H2O2: 0.033 mM) processes. Even when pressure-assisted ozonation (including three types of pressure processes with the combination of H2O2) was applied, PFOA and PFOS still could not be composed. This persistent and stable nature of PFCs was again shown in the wastewater treatment processes. Ten PFCs including perfluoroalkyl sulfonates (PFASs: PFBS, PFHxS and PFOS) and Perfluoroalkyl carboxylates (PFCAs: PFHxA, PFHpA, PFOA , PFNA, PFDA, PFUA and PFDoA) were detected in two municipal wastewater treatment plants (WWTPs) of Taipei city, the industry WWTP (IWWTP) of Shinchu Science Park, and upstream and downstream of IWWTP. PFOS (up to 293 ng/L) and PFHxA (up to 406 ng/L) were the major constituents of PFCs in municipal WWTPs. However, different distribution of PFCs was found in IWWTP. PFHxS (up to 2406.7 ng/L), PFOS (up to 6050 ng/L) and PFOA(up to 517.3 ng/L) were the major constituents of PFCs in effluent of IWWTP and its downstream rivers. This demonstrated that concentrations and composition of PFCs were much different between IWWTP and municipal WWTPs. Effluent of IWWTP and its downstream rivers have similar concentration levels of PFCs, which implies that the wastewater of IWWTP was the major source of PFCs to its downstream rivers. In addition, PFOA (2 ng/g), PFUA (4.1 ng/g)and PFDoA (15.8 ng/g)from sediment samples were detected in effluent of IWWTP and its upstream and downstream river. Ratios (sediment/water: (ng/kg)/(ng/L)) of PFOA, PFUA and PFDoA in downstream of IWWTP were 4, 766, and 6088 respectively, which shows that PFCAs with more carbons are adsorbed easier than PFCAs with less carbons. Consequently, most PFUA and PFDoA in the natural environment are attenuated by sorption onto sediments while more PFOA is found in the water bodies.