| 摘要: | 本研究評估H2O2/UV程序處理家庭污水一級出流水之特性，以台北縣家庭污水處理廠之初級沉澱池(一級)出流水為實驗用水樣，其水質濃度COD、DOC及SS分別為106-143、14.6-19.7及34-46 mg/L。實驗採批次式H2O2/UV反應槽，以pH、氧化時間、H2O2加藥量與UV照光強度為操作參數，以DOC、UV254與分子量分布等項目評估有機物氧化或礦化效果。研究結果顯示於pHs 3-4時之DOC與UV254去除率皆較pH 7時佳，此乃因於pHs 3-4較pH 7衍生較多氫氧自由基(OH．)所致。最適氧化時間為90-120分鐘時，DOC與UV254去除率與H2O2分解速率皆可以擬一階反應動力表示，且UV254去除率大於DOC去除率。此外，依H2O2加藥量與UV照光強度之條件不同，於氧化時間大約於120分鐘時，殘留DOC有增加趨勢，此乃因膠體性有機物被氧化成可檢測的(detectable)DOC所致。UV254去除率皆隨UV照光強度增加而提高；相對地，DOC與UV254去除率不隨H2O2加藥量增加而提高，存在一最適H2O2加藥量，此乃因過高H2O2加藥量因競爭OH．所致。由氧化處理後殘留之有機物(DOC)分子量變化，顯示高分子量(0.45μm-100 KD) DOC分解為中、低分子量DOC，且殘留DOC以低分子量(小於1 KD)DOC為主，佔95%以上。本研究處理家庭污水一級出流水之最適操作條件為pH 4、氧化時間為90分鐘、H2O2加藥量600 mg/L及UV照光強度96
Watts，DOC與UV254去除率分別達70與80%。
This study evaluated the treatability of domestic primary effluents by H2O2/UV oxidation process. The primary effluents were sampled from a wastewater treatment plant located at Taipei County. The concentrations of chemical oxygen demand (COD), dissolved organic carbon (DOC), and suspended solids (SS) were 106-143, 14.6-19.7, and 34-46 mg/L, respectively. All experiments were conducted in a batch H2O2/UV photo-reactor. The experimental parameters included pH, oxidation time, H2O2 dosage and UV intensity. The oxidation and mineralization of organics in water samples was demonstrated by the change in DOC, UV254, and molecular weight (MW) fraction of DOC.
The results showed that the removal of DOC at pHs 3-4 was better than that at pH 7 due to the higher production of hydroxyl free radicals (OH．). The optimum oxidation time ranged from 90 to 120 mins for the removals of DOC and UV254. The removal rates of DOC and UV254, and the degradation of H2O2 followed the pseudo-first-order kinetics. The removal of UV254 was faster than the removal of DOC. For most experimental conditions, the residual DOC showed a decreasing tend within first of the 90 mins oxidation time. In contrast, the residual DOC began to increase again as oxidation time was extended beyond 120 mins. This might be due to the colloidal organics being oxidized into detectable DOC. The removal of UV254 increased with increasing UV intensity and H2O2 dosage. Due to the competition for OH．between DOC and H2O2, the removal of DOC and UV254 did not increase with the increase of H2O2 dosage after an optimum H2O2 dosage had already been added. Furthermore, the DOC of a high molecular weight fraction was oxidized into DOC of medium and low MW fractions. After treatment, DOC of low MW(less than 1 KD) fractions predominated more than 95% of the residual DOC. It was concluded in this study that the optimal operational conditions for treating domestic primary effluents consisted of pH of 4, oxidation time of 90 min, H2O2 dosage of 400 mg/L and UV intensity of 96 watts. At the optimal operational condition, the removal DOC and UV254 reached 70 and 80%, respectively. |
