超濾膜與前處理技術於廢污水回收再利用之研究

Abstract

本研究以迪化污水處理廠二沉出流水、林口南區污水處理廠二沉出流水以及台大牧場之放流水為對象，利用中空纖維超濾膜（ultrafiltration, UF）進行廢污水回收再利用之可行性評估。並探討結合不同前處理技術，對廢污水中特定物質之去除效能。最後，根據薄膜清洗程序試驗，找出薄膜最佳操作條件。 以都市污水做為再生水水源時，薄膜操作條件為固定通量約20 LMH，過濾時間以不超過2小時，固定反沖洗流速為0.1 m/s，並且搭配玻璃纖維(fiber filter)過濾之前處理技術為最佳操作處理流程。經實驗結果得知，在無結合前處理之條件下，過濾2小時反沖洗1分鐘，經17小時過濾後TMP上升約280％；若結合玻璃纖維過濾和反沖洗步驟，其TMP上升約58％。 以工業廢水做為再生水水源時，薄膜操作條件為固定通量約20 LMH，反沖洗流速為0.1 m/s，過濾時間以不超過90分鐘為最佳操作流程。當結合玻璃纖維過濾和反沖洗步驟，觀察薄膜TMP之上升情形，結果顯示並無法有效減緩結垢生成。 以畜牧二級放流水做為水源，因懸浮固體物濃度超過50 mg/L，需藉由粒狀活性碳(granular activated carbon, GAC)預處理才能進入薄膜系統過濾。薄膜操作條件為固定產水通量約5 LMH，反沖洗流速為0.1 m/s，以過濾時間不超過15分鐘為最佳操作流程。實驗結果顯示，UF系統並不適合處理畜牧廢水。 分析不同廢污水經UF處理後之出流水水質，並與中階用水回收建議值比較；都市污水方面，僅pH值稍微偏低，其他數值皆可符合，另外，亦分析12種污水廠較常檢測出之高濃度新興污染物質，單獨以UF處理，其去除效果並不理想，需搭配其他前處理程序；工業廢水方面，處理後的水質無法符合冷卻用水回收建議值；至於畜牧廢水經處理後之濁度和電導度仍偏高，因此並不適合做為回收再生水水源。

The objective of the present study is to assess the feasibility of reusing ultrafiltration (UF) hollow-fiber membrane in the treatment of effluent of secondary domestic, industrial and pasturage wastewater. Simultaneously, kinds of pretreatment processes combined with UF were used to confer the removal efficiencies in term of turbidity, suspended solid, conductivity, inorganic matters and so on. Finally, collocate of backwash process with UF process was used as pretreatment to find the optimum operating conditions. For the secondary domestic wastewater, the UF system was designed to operate at constant flux and the backwashing rate of 20 LMH and 0.1 m/s respectively. Wastewater was filtered through UF for 2 hours, and then backwashed for 1 min. From the results it is clear that the optimum operating conditions could be achieved when fiber filter was combined with UF process and backwash process. For the secondary industrial wastewater, the UF system was designed to operate at a constant flux of 20 LMH with a backwashing rate of 0.1 m/s. Wastewater was filtered through UF for 90 min and followed by 1 min of backwash without any pretreatment. However, the results of transmembrane pressure (TMP) showed that this combination of processes could not decrease the membrane fouling effectively. Since the concentration of suspended solid in the secondary pasturage wastewater was 50 mg/L which was over the standard value, granular activated carbon (GAC) should be used for pretreatment process. In this study, the UF system was designed to operate at a constant flux of 5 LMH and with backwashing rate of 0.1 m/s. Wastewater was filtered through UF for 15 min and followed by 1 min of backwash. The results showed that the water quality of permeate for domestic wastewater treated by UF process was applicable to medium quality reuse. The water quality of industrial wastewater treated by UF process was not applicable to cooling water reuse. However, because the high concentration of turbidity and conductivity of wastewater from effluents of pasturage wastewater treatment, it is not suitable to use as the source of feedwater for wastewater reclamation.