臭氧結合離子交換程序再生廢污水之研究

Wastewater Recovery Using Ozonation Coupled with Ion-Exchange Process

周宗毅(Chung-Yi Chou)

指導教授 ： 於幼華

共同指導教授 ： 林正芳

國立臺灣大學/工學院/環境工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.03176

摘要

降雨是臺灣水資源的主要來源，在水資源的供給及需求漸漸出現失衡的現在，都市污水處理廠之放流水可做為傳統水源外的多元水源之一，然而放流水若無經適當處理即作為水源之用將可能造成多種風險，值得注意。本研究主題為：放流水再生處理之技術，利用離子交換程序置於臭氧程序後，以離子交換機制去除經臭氧程序產生較難處理的氧化副產物，藉此增進整體水再生處理之效率，另外，本研究亦針對合併處理程序（臭氧結合離子交換）之可能缺陷與操作成本進行評估，探討此合併處理科技之可行性。
研究結果顯示單獨以臭氧程序處理放流水之效果並不理想，初始pH = 3或7之1小時臭氧處理分別得到9%及43%的TOC去除率，最佳的處理效果為初始pH = 11之情況，但亦僅得TOC去除率49%，以一階反應模擬臭氧處理放流水之實驗結果得到欲使TOC去除率為95%需時長達10小時；以合併程序處理放流水之結果顯示：在初始pH = 3、7及11時30分鐘預臭氧的合併程序處理可得77%、94%及95%之TOC去除率，且臭氧處理確實可提昇其後離子交換程序對TOC之吸附能力，10分鐘之預臭氧處理可使離子交換程序增加去除約25% ~ 28% 的TOC，然而更長的預臭氧反應時間卻無法繼續增加離子交換程序所吸附的TOC；針對合併程序處理後之水質分析除TOC可得更進一步的處理外，水中陰陽離子（如NO3-N、Mg、Ca及Na等）亦可經由離子交換程序被移除，因而增加該合併程序的全面處理成效。
陰離子交換樹脂與臭氧反應後之體密度（濕）有縮小之趨勢，較原樹脂減少約10%，含水量或揮發性物質成份比例亦較原樹脂高，因此烘乾後重量較原樹脂減少20%；對甲酸、乙酸及草酸的吸附能力經由Langmuir等溫吸附模式之驗證，與臭氧反應後的樹脂對甲酸及乙酸的最大吸附容量顯有降低之趨勢，分別減少36%及24%，但對草酸則不明顯（僅5%）。
多種方式消減溶解臭氧以減少樹脂破壞之實驗結果顯示，臭氧消減速率之排序為：UV光照 > 外力消減（曝氣或超音波震盪）> 自然消減（初始pH為7及3），分別可得反應速率常數為：UV光照－1.3344 s-1、外力消減－0.2 ~ 0.4 s-1之間、自然消減－0.01 ~ 0.02 s-1之間，且溶解臭氧之消減均符合一階反應模式。
合併程序處理放流水至TOC去除率為94%時，操作成本經估算約為NT$ 17.7 ~ 49.8元/m3，較純以臭氧處理放流水節省NT$ 22 ~ 88.3元/ m3，平均約可節省操作成本達NT$ 49.8元/ m3，證實合併程序之經濟可行性。

關鍵字

臭氧 ； 離子交換 ； 再生水 ； 放流水 ； 經濟評估

並列摘要

Rainfall is the primary water resources for Taiwan. Under the unbalance between demand and supply of water, the effluents from municipal wastewater treatment plant could be alternative for water resources. However, risks will increase if people contact with the untreated effluents. The aim of this study is focused on the wastewater recovery technology of ozonation coupled with ion-exchange process to treat TOC in the effluents. The influences for the sorption abilities of ion-exchange resin following by ozonation and the economic analysis for the combined process have also been done.
The results show that ozonation, which provide the best of 49% TOC removal under 1 hr of reaction, is not a good choice for treating the effluent. The ozonation dynamics fitting with the first-order kinetic model show that almost 10 hr are needed for ozonating the effluent to 95% TOC removal. For the combined process, the treatment efficiency of the ion-exchange process in treating with TOC is indeed improved by the pre-ozonation treatment. 10 min pre-ozonation could improve 25% ~ 28% TOC removal by ion-exchange process. However, the difference in initial pH and more reaction time for the pre-ozonation, which increases the treatment efficiency of the combined process, show no improvements for the ion-exchange process in removing TOC. The analysis for the effluents treated by the combined process shows that not only TOC but also all the ions in effluents are removed, reflecting on the removal of conductivity from effluent.
The resin shrinks 10% in wet bulk density after reacting with ozone and 20% after it was dried under 105℃. The maximum sorption capacities for ormic acid and acetic acid of ozonated resin decrease 36% and 24% while only 5% decreasing is found in the sorption for oxalic acid of the ozonated resin. Few kinds of method are used in decomposing dissolved ozone in water: UV irradiation, forced decomposition (including gas dispersion and ultrasonic vibration) and nature decomposition (under initial pH of 3 and 7). The reactions following the first-order kinetic model have the reaction rate constant of 1.3344 s-1 for UV irradiation, 0.2 ~ 0.4 s-1 for forced decomposition and 0.01 ~ 0.02 s-1 for nature decomposition.
In economic analysis, the operation cost of combined process is about NT$ 17.7 ~ 49.8 for treating 1 ton of effluent. Comparing with the operation cost of ozonation, NT$ 22 ~ 88.3 per ton of effluent are saved.

並列關鍵字

ozone ； ion exchange ； wastewater recovery ； effluent ； economic assessment

參考文獻

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