Fouling characterization and control for harvesting microalgae Arthrospira (Spirulina) maxima using a submerged, disc-type ultrafiltration membrane

This study characterized the fouling of a novel circular-disc ultrafiltration membrane in a submerged bioreactor system to harvest Arthrospira maxima cells. Flux-stepping study showed that the value of critical flux was below the smallest flux tested at 28.8 l m−2 h−1, and that the membrane was to operate above the critical flux to sustain the necessary rate of cell concentration. The membrane with similar pore size but greater pore density experienced not only lesser degree of total resistance, but also possessed smaller fraction of irreversible resistance. Membrane fouling was mainly attributed to fragmented cells rather than to soluble or extracellular polymeric substances. Furthermore, flux recovery studies demonstrated that membrane relaxation and surface cleaning could partially recover fluxes for both low (6 g l−1) and high (40 g l−1) cell densities, whereas backwashing could fully recover fluxes. Calculation of energy consumption and cell harvesting productivity also favoured membrane filtration with backwashing.