生物薄膜系統中抗生物積垢之複合薄膜開發---製備及應用

Abstract

生物薄膜反應器 (membrane bioreactor, MBR)近年來引起廣泛的注意及應用，MBR 系統以薄膜單元取代傳統活性污泥程序中之沉澱池，因此有許多優勢，例如：佔地面積 較小、產生較少量之污泥及優良的出流水水質。但是薄膜積垢 (membrane fouling)卻大 大的限制MBR 的廣泛應用。薄膜積垢的發生會使得薄膜通量衰減並減少薄膜模組之壽 命，進而提高操作及維護成本。通常有以下幾種方式用於減緩MBR 之薄膜積垢：薄膜 表面改質、改善流況 (例如：增加水流剪力)及改善污泥特性。生長於薄膜表面之生物膜 被認為是造成MBR 積垢的主要原因之一。因此，對於薄膜表面之生物膜的瞭解將有助 於釐清MBR 系統中生物積垢的現象，並進一步的提出改善策略。 奈米級二氧化鈦為近期頗為熱門的光催化材料，其具有極高之親水特性並在紫外光 的激發下得以產生氫氧自由基，可以對於有機物進行光催化。本研究將提出以自行製備 之奈米級二氧化鈦溶膠 (sol-gel)對薄膜表面進行改質，利用所合成之複合薄膜較具親水 性特性，減緩薄膜積垢之發生 (以批次式stir-cell 驗證之)。並利用分子生物技術及共軛 焦雷射掃瞄顯微技術探討附著於表面之生物膜特性及其阻塞機制。此外，利用TiO2之 光催化特性，在側流式生物反應器中，以間歇性UV照光的方式光解附著薄膜表面上之 生物膜，並對於水中生物難分解性有機物進行降解，進一步提高生物薄膜系統之降解效 率及抗積垢能力。

By replacing a secondary clarifier with a membrane unit in an activated sludge process (ASP), membrane bioreactors (MBRs) have emerged as an innovative solution for wastewater treatment and reclamation. The application of MBR is constrained by membrane fouling. Fouling leads to permeation flux decline and increase in trans-membrane pressure (TMP), resulting in more frequent membrane cleaning and replacement, increasing operating costs. Common ways to minimize fouling in MBRs include modification of membrane, optimization of shear force on membrane surface, and improvement in sludge characteristics. It is widely known that the formation of biofilm on membrane surfaces is one of the major factors in membrane biofouling. Therefore, a better understanding of the nature of biofilm is key in revealing the characteristics of membrane biofouling in MBRs. Nano-scale titanium dioxide (TiO2) has been widely used in pollutant degradation and disinfection because TiO2 can easily produce hydroxide radical (OH˙). An innovative membrane surface modification method is to use nanosized TiO2 sol-gel. The nanosized TiO2 particles are hydrophilic, a property which can be adopted to modify the surface property of a membrane. The post-synthesis modification of the membrane can reduce membrane fouling by decreasing hydrophobic interaction between a membrane and sludge. Another purpose of this study is an attempt to elucidate the characteristics of biofilm formed on membrane surfaces and the mechanisms of biofouling caused by biofilm, using molecular biotechnology and confocal laser scanning microscopy (CLSM). The experiment of UV-irradiation of TiO2 on membrane surfaces is also investigated in a side-stream MBR. Intermittent photocatalytic reactions are practiced in the continuous MBR operation to inhibit the biofouling on membranes and degrade bio-refractory compounds.