(701f) Ultrafiltration Membranes and Modules for Microalgae Dewatering and Fouling Mitigation

Microalgae culturing is an effective way to utilize CO₂ and mitigate the CO₂ emissions to the atmosphere, and membrane technology has emerged as a key technology for microalgae dewatering, the most energy-intensive step in algae harvesting. However, the dewatering performance is subject to fouling by many components in the culturing solutions. Current studies regarding fouling are mostly conducted using a single model foulant, and there lacks an understanding of membrane fouling by the real algae products. In this work, we evaluated the dewatering performance of different commercial membranes and modules in dead-end cells and a cross-flow system. The effect of membrane pore size, algae concentration, membrane cleaning, and surface modification on the dewatering performance of the membrane coupons and modules were thoroughly investigated. Interestingly, ultrafiltration (UF) membranes exhibit greater steady-state dewatering permeance than microfiltration (MF) membranes despite lower pure-water permeance in the UF membranes. Increasing the algae concentration decreases the steady-state permeance of PSf-100. Nevertheless, when challenged by a feed containing 20 g/L algae, the PSf-100 still exhibited a water permeance of 687 LMH/bar. In multiple-cycle tests of fouling and cleaning, the polysulfone UF membrane (PSF-100) was cleaned by DI water or NaOH solution, and the cleaning efficiency of both methods reach 97%. Commerical membranes and modules were also modified by surface-grafting of superhydrophilic zwitterions to improve antifouling properties. The modified module shows water permeance 18% higher than the unmodified one. This study shows that membranes can achieve excellent dewatering performance and the surface modification can mitigate the fouling for the culture of microalgae.