Membrane Technology Group (MTG), Division cMACS, Faculty of Bio-Science Engineering, KU Leuven, Celestijnenlaan 200F, PO Box 2454, 3001 Leuven, Belgium.
Lab Aquatic Biology, Microbial en Molecular Systems, KU Leuven KULAK, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.
Water Res. 2021 Jun 15;198:117181. doi: 10.1016/j.watres.2021.117181. Epub 2021 Apr 22.
Membranes have a lot of potential for harvesting microalgae, but mainly membrane fouling and high harvesting costs linked to low fluxes are hampering their breakthrough. Patterned membranes can reduce fouling by enchancing local turbulences close to the membrane surface on one hand, and by increasing the active area per m of installed membrane on the other. Flocculation can further increase membrane permeance by increasing microalgal partical size and reducing the fraction of free organic matter in the feed. In current study, the effect of polyethylene glycol (PEG) in the casting solution of patterned polysulfone membranes was investigated to better tune the performance of the patterned membranes, together with the effects of cross-flow velocity and chitosan dosage on membrane fouling. The energy consumption and total harvesting cost, extrapolated to a full-scale microalgal harvesting, were then estimated. The patterned membrane prepared with a 28w% PEG concentration showed the highest clean water permeance (900±22 L/m h bar) and membrane permeance in a microalgal suspension (590±17 L/m h bar). Patterned membranes showed a lower filtration resistance (15% permeance decline at the end of filtration) than flat membranes (72%) at a cross-flow velocity of 0.0025 m/s. Increasing cross-flow velocity could increase membrane permeance in most cases. The highest stable membrane permeance (110±17 L/m h bar) and the lowest filtration resistance were achieved when combining patterned membrane filtration with flocculation at optimized chitosan dosage. A very low energy consumption (0.28 kWh/kg) and harvesting cost (0.16 €/kg) were achieved under these conditions.
膜在微藻收获方面具有很大的潜力，但主要的问题是膜污染和低通量导致的高收获成本，这阻碍了其突破。图案化膜一方面可以通过增强膜表面附近的局部湍流来减少污染，另一方面可以通过增加单位安装膜面积来提高通量。絮凝作用可以通过增加微藻颗粒尺寸和减少进料中游离有机物的比例来进一步提高膜的渗透性。在本研究中，考察了聚乙二醇（PEG）在图案化聚砜膜铸膜液中的作用，以更好地调节图案化膜的性能，并研究了错流速度和壳聚糖用量对膜污染的影响。然后估算了能量消耗和总收获成本，将其外推到微藻的全规模收获。在 28w%PEG 浓度下制备的图案化膜具有最高的清水通量（900±22 L/m h bar）和微藻悬浮液中的膜通量（590±17 L/m h bar）。与平膜（72%）相比，在 0.0025 m/s 的错流速度下，图案化膜的过滤阻力（过滤结束时通量下降 15%）较低。在大多数情况下，增加错流速度可以提高膜通量。在优化壳聚糖用量下，结合絮凝作用进行图案化膜过滤可获得最高的稳定膜通量（110±17 L/m h bar）和最低的过滤阻力。在这些条件下，能量消耗（0.28 kWh/kg）和收获成本（0.16 欧元/千克）非常低。
