| 摘要: | 本研究以某提供半導體及光電產業電子級化學品之化工廠為實例，探討將混有高濃度的各類化學品廢液以不同高級氧化程序作為預處理的可行性與效能比較。此研究之緣由為該廠如以既有的臭氧設備單獨進行廢水處理時，發現最終化學需氧量(COD)仍高達3,000 mg/L、去除率僅為49.2%，顯示處理效果不佳，因此本研究嘗試將臭氧與其他常見之高級氧化方法整併，應用不同的參數調整及疊加設計，試圖提升原有臭氧設備之效能，所納入的高級氧化方式包括UV / H2O2與芬頓(Fenton)反應。試驗結果以COD的去除率而言，處理效果依次為UV / H2O2 / O3 > UV / H2O2 > UV / H2O2 / Fe2+ > UV / O3，顯示UV / H2O2 / O3 的整合系統最適合去除該廠的高濃度有機化學品混合液。此UV / H2O2 / O3 系統的最佳操作結果為：初始COD = 6,060 mg/L、UV波長185 nm與254 nm、初始pH = 7.63、O3 = 32 g/hr、流速2 L/min、H2O2添加量72.72 g/L，反應8小時後COD去除率為98.2 %。此外，本研究發現除了COD去除可接近放流標準值，對於初始pH 4 ~ 7之條件下，此程序對於硝酸鹽氮及氨氮的降解並不顯著，應為廢液中之硝酸鹽類屬於高氧化態之含氮物種，故已無法與自由基反應氧化，而在8小時反應時間內，氨氮去除率所得之最佳結果為45 %。另設計搭配不同高級氧化程序進行參數調整之研究，在反應初期過程其pH皆呈現下降趨勢，可能原因為Fenton將Fe2+氧化成Fe3+容易與氫氧化物反應，造成酸累積，而後段反應產生碳酸氫根，導致pH值逐漸增加至8左右。對於硫酸根的變化，初始調整pH值則會造成硫酸根殘留量偏高達4,200 mg/L，而廢液中亞硫酸鹽應該是DMSO分解後產生的副產物，因此檢測硫酸根之變化可作為除臭之參考。最後，若以批次容量1噸設計、每月處理22噸計，此UV / H2O2 / O3系統回收年限約1.45年，其效益大於委外處理。;This study focuses on a chemical plant that provides electronic-grade chemicals for the semiconductor and optoelectronic industries. It explores the feasibility and effectiveness of using different advanced oxidation processes as pre-treatment for high-concentration chemical waste liquids. The motivation for this study stems from the inadequate results obtained when using the existing ozone equipment alone for wastewater treatment. The final chemical oxygen demand (COD) was still as high as 3,000 mg/L with a removal rate of only 49.2%. Therefore, this study attempts to enhance the efficiency of the existing ozone equipment by integrating it with other commonly used advanced oxidation methods, including UV/H2O2 and Fenton reactions. The experimental results show that in terms of COD removal rate, the treatment effectiveness follows the order of UV/H2O2/O3 > UV/H2O2 > UV/H2O2/Fe2+ > UV/O3, indicating that the UV/H2O2/O3 integrated system is most suitable for removing high-concentration organic chemical mixtures in the plant. The optimal operating conditions for this UV/H2O2/O3 system are as follows: initial COD = 6,060 mg/L, UV wavelengths of 185 nm and 254 nm, initial pH = 7.63, O3 = 32 g/hr, flow rate = 2 L/min, and H2O2 addition amount = 72.72 g/L. After 8 hours of reaction, the COD removal rate reaches 98.2%. Furthermore, this study finds that in addition to achieving COD removal close to the desired effluent standard, the process has insignificant degradation effects on nitrate nitrogen and ammonia nitrogen under initial pH conditions of 4 to 7. This is likely because the nitrate in the waste liquid belongs to highly oxidized nitrogen-containing species, making it no longer susceptible to oxidation by free radicals. Within the 8-hour reaction time, the optimal ammonia nitrogen removal rate obtained is 45%.
Additionally, a study on parameter adjustment using different advanced oxidation processes shows a decreasing trend in pH during the initial stage of the reaction. This may be due to the accumulation of acids caused by the oxidation of Fe2+ to Fe3+ in the Fenton reaction, which readily reacts with hydroxide ions. In the later stage of the reaction, bicarbonate ions are produced, leading to an increase in pH to around 8. Changes in sulfate ions indicate that adjusting the initial pH can result in a relatively high residual sulfate concentration of up to 4,200 mg/L. The presence of sulfite ions in the waste liquid is likely a byproduct of DMSO decomposition, making the monitoring of sulfate ion changes a reference for deodorization. In conclusion, if designed with a batch capacity of 1 ton and a monthly treatment capacity of 22 tons, the UV/H2O2/O3 system has an investment payback period of approximately 1.45 years, making it more beneficial than outsourcing treatment. |
