高級氧化前處理對消毒副產物生成之影響

Abstract

飲用水加氯消毒是台灣普遍採行之處理程序，然而氯會與水中有機物形成含氯消毒副產物，當水體有溴離子時則生成含溴消毒副產物，前者的致癌性與後者的生殖危害同樣值得重視。文獻指出pH 值、氯溴比及前質組成均影響消毒副產物之生成，然而文獻多關心單一參數或中性環境下之變化，缺乏整合各參數間之交互作用。本研究欲探討水中影響含氯、含溴消毒副產物生成之因素，並觀察以UV/H2O2前處理含溴水體後，消毒副產物生成潛能及物種分佈之變化。 前質試驗中選擇芳香族、脂肪族前質，添加不同濃度溴離子以改變氯溴比，分別觀察pH 7及pH 9之DBPFP濃度及物種分佈。發現任何條件下，芳香族前質僅生成含氯消毒副產物，可能因空間阻礙（steric hindrance）阻擋大分子HOBr與前質反應；脂肪族前質不具上述阻礙，易與反應速率較快之HOBr形成含溴消毒副產物。此外，芳香族前質偏好pH 7之環境，脂肪族前質則於pH 9較活躍。 本研究選擇金門太湖原水及實驗室配製前質作為實驗水樣，以UV及UV/H2O2前處理進行60∼120分鐘之氧化程序。UV反應過程中NPDOC無明顯變化，紫外光直接降解雙鍵導致DBPFP些微減少；UV/H2O2程序可有效降解NPDOC，然而DBPFP皆呈現先升後降之趨勢，在反應10分鐘達到最高點後才逐漸下降。可能由於氫氧自由基與有機物鍵結形成醇、酮類，增加水中消毒副產物之前質。 UV/H2O2程序不改變水中溴離子濃度，也不生成致癌性的溴酸鹽。若能確保高壓紫外燈之催化效率，有效縮短反應時間，UV/H2O2程序具應用於含溴金門原水之潛力。

Chlorination disinfection is a common water treatment process in Taiwan, generating toxic chlorinated disinfection by-products (DBPs). Unfortunately, Br-DBPs are also formed in presence of bromide. Cl-DBPs and Br-DBPs have received much public concern about their different health effects on carcinogenicity and reproduction damages. Therefore, the objective of this study is to evaluate bromide concentration, pH and precursor structures in drinking water to determine their influences on formation and distribution of THM and HAA. And this study also concerned about the changes of influencing factors and DBPFP in UV/H2O2 oxidation. Aromatic and aliphatic precursors and different bromide concentration were evaluated for the distribution of Cl-DBP and Br-DBP under chlorination at pH 7 and pH 9. Steric hindrance limited the aromatic precursors to Cl-DBPs under whole conditions. The aliphatic precursors tended to form Br-DBPs. Besides, the aromatic precursors were more reactive at pH 7, and the aliphatic one at pH 9. Tai lake water (Kinmen, Taiwan) and humic acids were selected in this study. In the UV/H2O2 process, THMFP or HAAFP increased within 10 min of irradiation and began to decrease after 30 min. OH-radicals seemed to increase DBPFP because which was not observed using UV irradiation without hydrogen peroxide. The bromide concentration remained stable and no bromate was formed under all irradiation time. The optimum effectiveness of UV/H2O2 process should be reached in application of bromide-rich Kinmen water.