King Abdullah University of Science and Technology, Water Desalination and Reuse Center, Thuwal, Saudi Arabia; Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
Water Res. 2014 Dec 15;67:227-42. doi: 10.1016/j.watres.2014.09.005. Epub 2014 Sep 16.
The influence of organic nutrient load on biomass accumulation (biofouling) and pressure drop development in membrane filtration systems was investigated. Nutrient load is the product of nutrient concentration and linear flow velocity. Biofouling - excessive growth of microbial biomass in membrane systems - hampers membrane performance. The influence of biodegradable organic nutrient load on biofouling was investigated at varying (i) crossflow velocity, (ii) nutrient concentration, (iii) shear, and (iv) feed spacer thickness. Experimental studies were performed with membrane fouling simulators (MFSs) containing a reverse osmosis (RO) membrane and a 31 mil thick feed spacer, commonly applied in practice in RO and nanofiltration (NF) spiral-wound membrane modules. Numerical modeling studies were done with identical feed spacer geometry differing in thickness (28, 31 and 34 mil). Additionally, experiments were done applying a forward osmosis (FO) membrane with varying spacer thickness (28, 31 and 34 mil), addressing the permeate flux decline and biofilm development. Assessed were the development of feed channel pressure drop (MFS studies), permeate flux (FO studies) and accumulated biomass amount measured by adenosine triphosphate (ATP) and total organic carbon (TOC). Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer thickness. The impact of the same amount of accumulated biomass on feed channel pressure drop and permeate flux was influenced by membrane process design and operational conditions. Reducing the nutrient load by pretreatment slowed-down the biofilm formation. The impact of accumulated biomass on membrane performance was reduced by applying a lower crossflow velocity and/or a thicker and/or a modified geometry feed spacer. The results indicate that cleanings can be delayed but are unavoidable.
研究了有机营养负荷对膜过滤系统中生物量积累（生物污垢）和压降发展的影响。营养负荷是营养浓度和线性流速的产物。生物污垢——膜系统中微生物生物量的过度生长——会妨碍膜的性能。研究了可生物降解有机营养负荷对生物污垢的影响，考察了不同的（i）错流速度、（ii）营养浓度、（iii）剪切和（iv）进料间隔层厚度。实验研究使用膜污染模拟器（MFS）进行，其中包含反渗透（RO）膜和 31 密耳厚的进料间隔层，这在 RO 和纳滤（NF）螺旋缠绕膜组件的实际应用中很常见。数值模拟研究使用具有不同厚度（28、31 和 34 密耳）的相同进料间隔层几何形状进行。此外，还使用具有不同间隔层厚度（28、31 和 34 密耳）的正向渗透（FO）膜进行了实验，以解决渗透通量下降和生物膜发展问题。评估了进料通道压降（MFS 研究）、渗透通量（FO 研究）和通过三磷酸腺苷（ATP）和总有机碳（TOC）测量的累积生物量的发展。我们的研究表明，有机营养负荷决定了生物量的累积量。在恒定的营养负荷下，无论线性流速、剪切和/或进料间隔层厚度如何，都会发现相同数量的累积生物量。相同数量的累积生物量对进料通道压降和渗透通量的影响取决于膜过程设计和操作条件。预处理通过降低营养负荷可以减缓生物膜的形成。通过应用较低的错流速度和/或较厚的和/或修改的进料间隔层几何形状，可以减少累积生物量对膜性能的影响。结果表明，清洁可以延迟但不可避免。
