King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological & Environmental Science & Engineering Division (BESE), Thuwal, 23955-6900, Saudi Arabia.
FujiFilm Manufacturing Europe B.V, Oudenstaart 1, 5047, TK, Tilburg, the Netherlands.
Water Res. 2019 Nov 15;165:114985. doi: 10.1016/j.watres.2019.114985. Epub 2019 Aug 13.
Low pressure membranes, such as ultrafiltration (UF), are widely used in water treatment applications, including the pretreatment of reverse osmosis desalination. UF membranes produce a water of superior quality, in addition to reducing the footprint and the use of chemicals, compared to conventional methods. However, membrane fouling remains a major drawback, and frequent membrane cleanings are required to maintain the flux of water and its quality. Typically, after a series of backwashes using an UF permeate, a chemical cleaning process is applied to fully recover the membrane's permeability. However, frequent chemical cleanings negatively affect the lifetime of the membrane, the environment, and increase operational costs. Here, we introduce a novel cleaning method that uses a solution saturated with CO to clean the membranes through the backwash step. As the pressure drops, the CO solution becomes supersaturated, and bubbles start to nucleate within the membrane pores and on its surface, resulting in the effective removal of the deposited fouling material. These foulants are further helping the nucleation process as they are considered as imperfection sites with high creation and growth of bubbles. Investigations performed for different synthetic feed solutions of organic compounds (sodium alginate), colloidal matter (silica) and sea salts, at different concentrations, show that our new physical cleaning process using CO is more performant than the regular backwash using Milli-Q water. We obtain a 100% flux recovery, in a short time, even under severe irreversible fouling conditions. Based on these results, we conclude that replacing water by a solution saturated with CO for the backwash cleaning of filtration membranes provides significant benefits to existing cleaning processes, and represent a promising alternative for improving and lowering the frequency of conventional chemical cleaning methods.
低压膜，如超滤（UF），广泛应用于水处理应用中，包括反渗透脱盐的预处理。与传统方法相比，UF 膜不仅减少了占地面积和化学品的使用，还生产出优质的水。然而，膜污染仍然是一个主要的缺点，需要频繁进行膜清洗以保持水的通量和质量。通常，在使用 UF 渗透液进行一系列反冲洗之后，会应用化学清洗工艺来完全恢复膜的渗透性。然而，频繁的化学清洗会对膜的寿命、环境和运营成本产生负面影响。在这里，我们介绍了一种新的清洗方法，该方法使用 CO 饱和溶液通过反冲洗步骤来清洗膜。随着压力下降，CO 溶液会过饱和，并且气泡开始在膜孔内和表面上成核，从而有效地去除沉积的污垢物质。这些污染物进一步有助于成核过程，因为它们被认为是具有高气泡形成和生长的缺陷位点。对于不同浓度的合成有机化合物（海藻酸钠）、胶体（二氧化硅）和海水盐等合成进料溶液进行的研究表明，我们使用 CO 的新物理清洗工艺比使用 Milli-Q 水的常规反冲洗更有效。即使在严重的不可逆污染条件下，我们也可以在短时间内实现 100%的通量恢复。基于这些结果，我们得出结论，用 CO 饱和溶液代替水进行过滤膜的反冲洗清洗，可以为现有清洗工艺带来显著的益处，并为改进和降低传统化学清洗方法的频率提供了有前途的替代方案。
