UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, Netherlands; Wetsus Center of Excellence for Sustainable Water Technology, Agora 1, 8934 CJ Leeuwarden, Netherlands.
UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, Netherlands.
Water Res. 2015 Mar 1;70:300-12. doi: 10.1016/j.watres.2014.12.012. Epub 2014 Dec 16.
Transparent exopolymer particles (TEP) and their precursors produced by phyto-/bacterio-planktons in fresh and marine aquatic environments are increasingly considered as a major contributor to organic/particulate and biological fouling in micro-/ultra-filtration and reverse osmosis membrane (RO) systems. However, currently established methods which are based on Alcian blue (AB) staining and spectrophotometric techniques do not measure TEP-precursors and have the tendency to overestimate concentration in brackish/saline water samples due to interference of salinity on AB staining. Here we propose a new semi-quantitative method which allows measurement of both TEP and their colloidal precursors without the interference of salinity. TEP and their precursors are first retained on 10 kDa membrane, rinsed with ultra-pure water, and re-suspended in ultra-pure water by sonication and stained with AB, followed by exclusion of TEP-AB precipitates by filtration and absorbance measurement of residual AB. The concentration is then determined based on the reduction of AB absorbance due to reaction with acidic polysaccharides, blank correction and calibration with Xanthan gum standard. The extraction procedure allows concentration of TEP and their pre-cursors which makes it possible to analyse samples with a wide range of concentrations (down to <0.1 mg Xeq/L). This was demonstrated through application of the method for monitoring these compounds in algal cultures and a full-scale RO plant. The monitoring also revealed that concentrations of the colloidal precursors were substantially higher than the concentration of TEP themselves. In the RO plant, complete TEP removal was observed over the pre-treatment processes (coagulation-sedimentation-filtration and ultrafiltration) but the TEP precursors were not completely removed, emphasising the importance of measuring this colloidal component to better understand the role of TEP and acidic polysaccharides in RO membrane fouling.
透明胞外聚合物颗粒（TEP）及其在淡水和海洋水生环境中由浮游植物/细菌产生的前体越来越被认为是微滤/超滤和反渗透膜（RO）系统中有机/颗粒和生物污染的主要贡献者。然而，目前基于吖啶蓝（AB）染色和分光光度技术的方法无法测量 TEP 前体，并且由于盐度对 AB 染色的干扰，在咸水/盐水样品中存在浓度过高的趋势。在这里，我们提出了一种新的半定量方法，该方法可以在不干扰盐度的情况下测量 TEP 和它们的胶体前体。TEP 和它们的前体首先被保留在 10 kDa 膜上，用超纯水冲洗，然后通过超声处理重新悬浮在超纯水中，并与 AB 染色，随后通过过滤排除 TEP-AB 沉淀物并测量残留 AB 的吸光度。然后根据与酸性多糖反应导致的 AB 吸光度降低、空白校正和黄原胶标准校准来确定浓度。该提取程序允许浓缩 TEP 和它们的前体，从而可以分析浓度范围很广的样品（低至 <0.1 mg Xeq/L）。通过将该方法应用于藻类培养物和全规模 RO 工厂中这些化合物的监测来证明这一点。监测还表明，胶体前体的浓度远高于 TEP 本身的浓度。在 RO 工厂中，在预处理过程（混凝-沉淀-过滤和超滤）中观察到完全去除 TEP，但 TEP 前体未完全去除，这强调了测量这种胶体成分的重要性，以更好地了解 TEP 和酸性多糖在 RO 膜污染中的作用。
