臭氧去除超濾薄膜積垢之研究; Fouling Removal from Ultrafiltration Membrane by Ozonation

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Title:	臭氧去除超濾薄膜積垢之研究;Fouling Removal from Ultrafiltration Membrane by Ozonation
Authors:	徐偉峻;Wei-Chun Hsu
Contributors:	環境工程研究所
Keywords:	三級處理水;超濾;薄膜積垢;臭氧;結垢;ultrafiltration;membrane fouling;scaling;ozone;tertiary treatment water
Date:	2005-06-21
Issue Date:	2009-09-21 12:16:49 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以工業區綜合污水處理廠之三級處理水為對象，探討以抗臭氧氧化之超濾(UF)(polyvinylidene fluoride, PVDF)薄膜處理時，膜面之積垢程度及種類，並以臭氧去除UF膜面積垢之方法與可行性。研究內容，首先探討三級處理水之水質特性，以評估薄膜積垢之程度及種類，並建立UF薄膜初始通量、本身阻抗及孔隙大小等薄膜基本特性。最後藉由實驗室薄膜系統模組之批次實驗，探討進流水預臭氧化、臭氧加入進流水及臭氧加入反洗水，三種不同的臭氧除垢方式，對臭氧去除薄膜積垢之影響，提供實廠操作之參考。研究結果顯示，工業區綜合污水處理廠三級處理水，經5μm預濾後，再經UF過濾前後水質發現，UF對於鐵、錳及SDI去除率分別為62%、30%及88%；而膜面積垢之FTIR分析結果顯示，主要組成之有機官能基，為染料發色團及助色團中的芳香族化合物，及少數直鏈化合物，因此可知以三級處理水為UF飼水時，可能造成膠體積垢及有機積垢。由薄膜系統進流水預臭氧化實驗發現，預臭氧能改善三級處理水及UF滲透液水質，臭氧氣相質量流率控制在13.99 mg/min下，隨著預臭氧時間的增加，水質改善及UF過濾效果也跟著增加，在預臭氧4分鐘，三級處理水及UF滲透液中鐵的去除率，分別為62%及100%，平均粒徑也分別由682 nm降至380 nm及400 nm降至280 nm，滲透液通量能由初始通量的60%增加至80%。然而，接著預臭氧時間再增加，水質及過濾效果反而下降。由臭氧加入薄膜系統進流水實驗結果發現，若薄膜阻塞後，再於進流水中添加臭氧，僅能將滲透液通量由初始的60%提升至80%，但是，若在進流水中持續添加臭氧，則能將滲透液通量，維持在約初始通量的90%。因此，持續添加臭氧於進流水，可有效減緩薄膜積垢。而由臭氧加入薄膜系統反洗水實驗發現，連續過濾反洗120分鐘後，滲透液通量也可維持在初始通量的90%。上述三種不同的臭氧除垢方式中，以臭氧持續加入進流水及反洗水，為減緩薄膜積垢之較適操作方式。整體而言，由三級處理水預臭氧前後之粒徑分佈結果可知，造成滲透液通量提升之原因為分子降解及顆粒去穩定化。此外，臭氧加入後會增加水中含氧官能基，進而增加三級處理水之極性，而PVDF材質薄膜為一疏水性薄膜，因此可減低疏水性物質吸附於膜面之程度。而由臭氧加入進流水前後FTIR分析結果可知，臭氧去除有機積垢之機制主要為芳香族化合物環狀結構的破壞及大分子有機物的斷鍵。臭氧去除無機結垢之機制主要為有機物被臭氧氧化形成的官能基與水中之陽離子錯合，增加結垢物種的溶解度。 The objectives of this study are aimed to investigate the degree and kind of membrane fouling formed from the ultrafiltration (UF) of the tertiary treatment water in an industrial park, and to evaluate the feasibility of removing membrane fouling by ozone. The material of membrane used in the experiments was polyvinylidene fluoride (PVDF), as it could resist the corrosion of ozone. In order to assess the degree and kind of membrane fouling, the first step was to investigate the water quality characteristic of the tertiary treatment water and then set up the basic characteristics of the membrane, such as the initial permeate flux, the membrane resistance, and the pore size of UF membrane. In order to offer the reference for the real factory operation, a bench-scale membrane system was performed in the experiments to evaluate the fouling removed by three kinds of different ozonation, such as influent preozonation, ozone in-line dosing and ozone backwashing. Experimental results showed that the removal efficiency of iron, manganese and SDI was 62%, 30% and 88%, respectively, after the 5µm prefiltration and UF without ozone. From the FTIR analysis of membrane fouling, results showed that the organic functional groups were aromatic rings and a few linear chain compounds of chromophore and auxochrome in dyestuff. So the tertiary treatment water may induce the colloidal fouling and organic fouling in the UF system. Experimental results also showed that preozonation could improve the tertiary treatment water and UF permeate quality. When the time of preozonation was increased more, improvement of water quality and effect of UF were enhanced more. When the ozone gas mass flow rate was 13.99 mg/min and the time for preozonation was 4 minutes, the removal efficiency of iron in the tertiary treatment water and the UF permeate was 62% and 100%, and meanwhile, the average particle size of the former decreased from 682nm to 380nm and the latter decreased from 400nm to 280nm, and the permeate flux increased from 60% to 80% of the initial flux, respectively. However, when increasing the preozonation time more, the water quality and the effect of filter were worse. It was observed that when injecting into influent by ozone after blocked of the membrane, the permeate flux only increased from 60% to 80% of the initial flux. But, it was observed that when injecting into influent by ozone continuously, the permeate flux could maintained to 90% of the initial flux. It is demonstrated that the effect of the former is better than the latter. It was also observed that the permeate flux still maintained to 90% of initial permeate flux about 120 minutes from the beginning by ozone backwashing. According the above investigation, ozone in-line dosing and ozone backwashing are more suitable for inhibiting the membrane fouling. On the whole, the reason why the permeate flux could be increased within ozonation were the molecular degradation and the particle destabilization. Moreover, ozonation could produce the oxygenated functional groups and increase hydrophile of tertiary treatment water. Because PVDF material was a hydrophobic membrane, so it could reduce the hydrophobic matter absorbed on the membrane surface. Comparing the FTIR analysis of fouling without and with ozone, the removal mechanism of organic fouling with ozonation was the destruction of aromatic ring and the breaking of macromolecule organic matters. The removal mechanism of inorganic fouling was also the ozonation of organic matter. The ozonation might produce the oxygenated functional groups that might couple with cations to form complexes and increase the solubility of scaling matters.
Appears in Collections:	[Graduate Institute of Environmental Engineering ] Electronic Thesis & Dissertation

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