飲用水處理步驟移除類固醇雌激素雌激素之效率

Abstract

天然動情激素（E2）與其代謝物－雌素酮（E1）、雌素醇（E3），以及人工合成雌性激素－乙炔動情激素（EE2）具有生物活性，可能廣泛影響環境水體生態。目前針對減少這類化合物排放之探討，著重在污水處理廠之移除效率；然而對於以河水、水庫作為飲用水水源的我們，對飲用水處理單元是否能夠有效去除雌激素所知極為有限。 本研究以淨水場之原水為基質，添加100或500 ng/L之雌激素標準品，然後於實驗室模擬前加氯、混凝沉澱、快濾及後加氯等典型之淨水程序，以瞭解各處理單元對於移除類固醇雌激素之效率；並同時調查台北市長興淨水場原水及清水中雌激素的濃度。樣本以固相萃取結合液相層析/質譜/質譜儀進行定量分析。 在前加氯單元，E1、E2、EE2及E3之平均去除率約在20－40％；混凝沉澱則可移除17－52％ 的雌激素；快濾單元部份，除E3外，其餘皆有95 ％ 以上的去除率；在後加氯方面，四種化合物之去除率變異較大，去除率約在17－44％。顯然地，快濾機制的移除效果遠優於其他淨水單元（ p＜0.001）。另外經全流程處理之後，E1、E2和EE2的去除率皆大於88％，E3去除效果較差，低於84％。 濃度對去除率的影響，E1和E3在四個處理單元的去除率皆無明顯差異；E2在前加氯及混凝/沉澱二個單元則有統計上之差異（ p ＜0.05），前加氯單元以高濃度時去除效果較佳，混凝/沉澱單元則反之；EE2的移除只在後加氯單元受濃度差異之影響（ p ＝ 0.002）；E3之移除率在快濾及後加氯單元雖未達顯著差異（ p ＝ 0.053與0.059），但平均去除率皆相差約9％。全流程處理後，只有E3受濃度差異之影響（ p ＝ 0.002）。 各化合物間去除趨勢顯示，在500 ng/L濃度，前加氯單元，E2去除效果顯著大於E3（ p ＝ 0.031）；混凝/沉澱單元中四種化合物間均未達統計上之差異；快濾單元及全流程單元，E3去除率亦顯著小於E1、E2及EE2（ p ＜0.001）。另外經全流程處理之後，E1、E2和EE2的去除率皆大於88％，E3去除效果較差，低於84％。 濃度對去除率的影響，E1和E3在四個處理單元的去除率皆無明顯差異；E2在前加氯及混凝/沉澱二個單元則有統計上之差異（ p ＜0.05），前加氯單元以高濃度時去除效果較佳，混凝/沉澱單元則反之；EE2的移除只在後加氯單元受濃度差異之影響（ p ＝ 0.002）；E3之移除率在快濾及後加氯單元雖未達顯著差異（ p ＝ 0.053與0.059），但平均去除率皆相差約9％。全流程處理後，只有E3受濃度差異之影響（ p ＝ 0.002）。 各化合物間去除趨勢顯示，在500 ng/L濃度，前加氯單元，E2去除效果顯著大於E3（ p ＝ 0.031）；混凝/沉澱單元中四種化合物間均未達統計上之差異；快濾單元及全流程單元，E3去除率亦顯著小於E1、E2及EE2（ p≦0.001）；後加氯單元中此四者間亦無達統計上之差異。在100 ng/L濃度部分，四種化合物在各處理單元之去除趨勢並無一致，除混凝/沉澱單元中E2去除效果顯著大於EE2外（ p ＝ 0.028），其餘皆無統計上之顯著差異。 淨水場之原水有些樣本可偵測到微量之E1、E2、EE2及E3；在高於偵測極限的樣本中，平均濃度為1.57－2.37 ng/L；但是在淨水場出水樣本中，四個化合物含量皆低於偵測極限（＜0.06－0.15 ng/L）。 本研究顯示淨水場各處理單元移除雌激素之效率的確有所差異；整體而言，淨水流程可去除大部份的雌激素，且原水中之含量屬極微量，因此民眾經由此途徑之暴露應可忽略。

The native estrogenic steroid 17β-estradiol ( E2 ) and it’s metabolites, estrone ( E1 ) and estriol ( E3 ), and the synthetic steroid 17α-ethinyl estradiol（EE2）may distribute to water bodies and impact the eco-system with their estrogenic potency. Most studies focus on the removal efficiency of the sewage treatment plants regarding their emissions; however, there is limited information on the elimination of estrogenic chemicals during drinking water treatment processes. This research investigated the removal rates of drinking water treatment units by spiking two levels（100 and 500 ng/L）of the four estrogens into raw water. Four processes were simulated in the laboratory to evaluate the removal efficiencies：pre-chlorination, coagulation/sedimentation, rapid filtration, and post-chlorination. The study also reported the concentrations of the four estrogens in the raw water and treated water. Solid-phase extraction and LC/MS/MS with isotope-dilution techniques were utilized to analyze the four chemicals. 20－40％ of E1, E2, EE2 and E3 were removed in the pre-chlorination unit; the coagulation/sedimentation procedure eliminated 17－52％ of the chemicals, and E2 was the highest. The rapid filtration step took out over 95％ of the compounds expect for E3 ( 84－92％). The removal efficacy in post -chlorination process varied widely, which was 17－44％, and E2 was the lowest one. Obviously, the rapid filtration treatment is superior to the other processes in removing the chemicals ( p＜0.0001 ). The whole procedure got rid of over 88％ of the chemicals excluding the E3 ( 64－85％ ). In terms of the influence of spiked levels, there is no significant difference of E1 and E3 removal among the four processes, but it was significant for E2 in the pre-chlorination and coagulation/sedimentation units ( p＜0.05 ). For E2, better efficiencies were observed at 500 ng/L in the pre-chlorination； however, the removal efficacy of coagulation/ sedimentation unit was higher at 100 ng/L. For EE2, there was only difference in the post-chlorination step ( p＝0.002 ). The elimination rates between these two spiked levels for E3 in the rapid filtration treatment and post-chlorination units and almost reach statisitical significance ( p＝0.053 and 0.059 ). Spiked levels did not influence the elimination performance through the whole procedure except for E3 ( p＝0.002 ). At 500 ng/L level, the removal efficacy of E3 was much lower than that of E2 in pre-chlorination ( p＝0.031 ), the removal percentage of E3 was also notably lower than those of E1, E2 and EE2 in rapid filtration and through the complete process ( p ≦0.001 ). There was no statistical difference among the removal rates of the four compounds in the coagulation/sedimentation and post-chlorination units. Regarding the 100 ng/L level, the removal efficiencies of the four units for the four estrogenic compounds varied. Nevertheless, the only difference in the removal efficacy for the four compounds was the coagulation/sedimentation, which E2 was taken away much more than EE2 ( p＝0.028 ). The four steroid estrogens were detected from same raw waters. Among the detected samples, the average levels were 1.57－2.37 ng/L. On the other hand, none of the four compounds was detected in the treated drinking water.