陳慧雯－以UV/H2O2程序處理水中有機物之研究
Decomposition of Organic Matters in Aqueous Solution by UV/H2O2 process
Back

自來水廠對於水中有機物之處理多經過沈澱、混凝、過濾及加氯消毒以去除之，但傳統程序對有機物的處理效果並不佳，而且氯會與水中有機物質形成有害的消毒副產品，對健康有潛在的危害；而UV/H₂O₂程序可將有機物完全礦化，且不會產生消毒副產品，本研究即在探討UV/H₂O₂程序在不同的條件下（pH值、H₂O₂濃度、鹼度、濁度、大分子有機物）氧化水中有機物之效率，並探討程序使用於自來水處理之可行性。

本研究利用台大醫院廢水處理廠未加氯放流水及實驗室配置腐植酸作為實驗水樣，以UV/H₂O₂程序進行2小時的氧化反應；在廢水系統中，未過濾的二級放流水由於含有多量大分子有機物，氫氧自由基主要的作用在於分解大分子有機物，使得水中NPDOC降解曲線呈現上升趨勢，必須先將廢水過濾再進行處理才能得到較佳的氧化效果。影響過濾的廢水有機物去除效率最大之因素為加入H₂O₂之劑量，試驗結果顯示最佳劑量為0.01∼0.1 ％，處理2小時可達到80％的去除率；酸鹼值對於廢水溶液之影響並不大，而鹼度的增加會使NPDOC的去除率略為下降。

腐植酸溶液中，影響處理效率最大的因素亦在於H₂O₂加入的劑量，最佳劑量為0.01∼0.05％，處理2小時可達到95％的去除率，黃酸的氧化結果與腐植酸相似；pH值的改變不會對NPDOC降解造成影響，而增加鹼度會使NPDOC的去除率略為下降，濁度提高至10NTU亦不會降低降解效率；觀察H₂O₂的降解，僅與其加入劑量相關，H₂O₂初始濃度高者（＜0.1％）為零次反應，初始濃度低則為一次反應。隨著水樣被氧化，水溶液的pH值會呈現下降的趨勢，應是有機物被分解成小小分子酸的結果。

程序並不能有下的去除板新原水中的NPDOC，應是因為有機物濃度較低，而六堵原水的NPDOC亦僅能去除60％。在處理金門原水，若先將原水過濾再行氧化，則有良好的NPDOC去除效果。

The presence of natural organic matter in surface water supplies has received much public attention in recent years because toxic disinfection byproducts (DBPs) can result from chlorination procedures in the water treatment processes. In this study, a batch photoreactor was used to evaluate the UV/H2O2 oxidation process for the removal of humic acids in water. The photolysis of the organic pollutants in the secondary efferent of hospital wastewater treatment plant was also studied. Raw water from Liu-Du, Ban-Hsin, and Kin-Men water treatment plants were also evaluated for the effectiveness of UV/H2O2 oxidation in this study for comparison. A 450-watt UV lamp with high-pressure mercury vapor was employed as the light source. The residues of organic compounds (measured as non-pergeable dissolved organic carbon) and hydrogen peroxide were measured for assessment of process performance and understanding of process reaction behavior. The UV photolysis alone can play an important role in the degradation of humic acids. The presence of hydrogen peroxide was found to promote the degradation efficiency. However, excessive dosage of H2O2 does not further improve the degradation of humic acids, on the contrary, the lower the H2O2 dosage the higher the amount of humic acids can be removed. The decomposition of H2O2 depends on its initial concentrations. At higher H2O2 concentration (>0.1%), H2O2 decomposition follows zero-order reaction; at lower H2O2 concentrations, its decomposition is first-order. As reaction proceed, the pH value drop slightly because the degradation of the organic substances to small molecular acids. The presence of carbonate species deteriorates the organic removal, whereas it results in a larger amount of H2O2 decomposition.