超音波結合芬頓程序處理廢水中難分解有機物： 以化工廠廢水為例

Abstract

工業廢水中往往存在大量難分解有機物，而導致生物處理法去除污染物之效率不彰，必須以高級氧化處理程序(Advanced oxidation processes, AOPs)方能有效去除。其中以傳統芬頓程序(Fenton)處理費用較便宜而廣為實場應用，然而其對於污染物處理效率有限，且反應過程伴隨大量污泥生成而造成後續處理負擔。因此本研究利用超音波結合芬頓程序(ultrasound aided Fenton process, US/Fenton)處理廢水中難分解有機物以改善芬頓程序之缺點。實驗中首先與不同氧化處理程序比較，如超音波氧化法、芬頓氧化法、超音波結合亞鐵離子、過氧化氫或二氧化鈦之程序，並以溶解性總有機碳(TOC)及化學需氧量(COD)之去除率評估系統效能。研究結果顯示超音波╱芬頓程序對於目標廢水之難分解有機物不僅能有效礦化，並將部分難以礦化之有機物氧化成較高氧化態之中間產物，且減少Fe(OH)3污泥。本研究之目標污染物為採用合成樹脂、橡膠業之化工廢水，有機污染物定性結果顯示，此股化工廠廢水中難以被微生物分解之有機物主要為鄰苯二甲酸二辛酯(DOP)及烷類化合物，於經過超音波╱芬頓程序反應180分鐘能有效將污染物降解成小分子之化合物。 於超音波╱芬頓處理程序中，最佳操作條件為添加劑量為過氧化氫200 mM及亞鐵離子5 mM；輸出強度為35.4 W/cm2；反應時間為60分鐘；反應槽半徑1.25公分；探頭沒入深度為2.5公分，其溶解性TOC及COD去除率分別可達55.2%及77.0%。在經濟評估方面，比較超音波╱芬頓與工業用芬頓程序(H2O2/Fe2+＝1)，以其污染物去除率相近為基準，其處理費用相近，顯示此程序具有放大規模之可行性。

Due to a large amount of refractory organics in the industrial wastewater, biological treatment processes are not effective to degrade the organic pollutants in the industrial wastewater. Therefore, advanced oxidation processes (AOPs) are usually used for degradation of such refractory organic pollutants. Of all AOPs for treating wastewater, traditional Fenton process has been widely used because of the cheaper costs than others. However, excess sludge is produced in Fenton process. To minimize the sludge production and increase the removal efficiency, we used ultrasound-aided Fenton process (US/Fenton) to treat the refractory organics in wastewater. The TOC and COD removal rates of US/Fenton were compared with those of other oxidation processes, including ultrasound (US) , Fenton, and ultrasound combining with Fe2+, H2O2 or TiO2. The results showed that US/Fenton process had the best TOC and COD removal efficiency. US/Fenton process can not only increase the mineralization rate of organics but oxidize the refractory organics into intermediate products, as well as reduce the amount of Fe(OH)3 sludge. According to the qualitative analysis, the results showed that 1,2-benzenedicarboxylic acid, bis (2-ethylhexyl) ester (DOP) and alkane compounds were the main refractory organics in this industrial wastewater and these compounds could be decomposed into smaller molecules after 3 hours by US/Fenton process. The optimum operating conditions of the US/Fenton are as follows, the [H2O2] = 200 mM, [Fe2+] = 5 mM, the intensity of ultrasound = 35.4 W/cm2; reaction time = 1 h; radius of reactor = 1.25 cm; the depth of probe immersed = 2.5 cm. Under this optimum operating conditions, the TOC and COD removal rates were 55.2% and 77.0%, respectively. In terms of economy assessment, comparing US/Fenton in this study with Fenton applied in industry (H2O2/Fe2+ = 1), the operating costs are similar under similar contaminants removal. As a result, US/Fenton process is feasible to scale up and apply in full scale treatment plants.