Investigation of severe UF membrane fouling induced by three marine algal species

Abstract

Reducing membrane fouling caused by seawater algal bloom is a challenge for regions of the world where most of their freshwater is produced by seawater desalination. This study aims to compare ultrafiltration (UF) fouling potential of three ubiquitous marine algal species cultures (i.e., Skeletonema costatum-SKC, Tetraselmis sp.-TET, and Hymenomonas sp.-HYM) sampled at different phases of growth. Results showed that flux reduction and irreversible fouling were more severe during the decline phase as compared to the exponential phase, for all species. SKC and TET were responsible for substantial irreversible fouling but their impact was significantly lower than HYM. The development of a transparent gel layer surrounding the cell during the HYM growth and accumulating in water is certainly responsible for the more severe observed fouling. Chemical backwash with a standard chlorine solution did not recover any membrane permeability. For TET and HYM, the Hydraulically Irreversible Fouling Index (HIFI) was correlated to their biopolymer content but this correlation is specific for each species. Solution pre-filtration through a 1.2 μm membrane proved that cells and particulate algal organic matter (p-AOM) considerably contribute to fouling, especially for HYM for which the HIFI was reduced by a factor of 82.3.

Advanced characterization of dissolved organic matter released by bloom-forming marine algae

“…2 and Table 2). Consistent with other studies [21,22,38], AOM production increased mainly due to increase in BP concentration during the cultivation period. For all three species, DOC concentration decreased from day 0 to day 4 (lag phase), as the concentration of LMW acids and neutrals decreased (24%, 42% and 64% for Hym, CA and NZ, respectively).…”

“…At stationary/death phase, CA had the highest ratio of BP to DOC, followed by Hym and NZ (40%, 30% and 20%, respectively). Similar ratios were reported for Hym and CA in the literatures [22,41].…”

“…The difference in the length of lag phase for Hym in this and a recent study may be attributed to the age of the inoculum [22]. For CA, a lag phase of 12 d was observed, followed by a relatively short exponential growth phase, after which the stationary/ death phase began at day 20.…”

“…A number of studies have shown a correlation between the polysaccharide fraction of AOM and MF/UF membrane fouling [17][18][19][20]. Since AOM from different algae have different fouling potential and mechanisms [21,22], it is important to analyze the structure and composition of algal PS released by different species for a better understanding of the interaction of these compounds with membrane surfaces. Using lectin staining and microscopy, it was found that AOM from different algal species contained different functional groups [21].…”

From lab to full-scale ultrafiltration in microalgae harvesting

“…Ultrafiltration (UF) is a pressure-driven membrane process which is generally used in water treatment, wastewater treatment, biotechnology, food processing, etc. In microalgae harvesting, UF is the most promising techniques for concentrating microalgae [19][20][21][22][23][24][25][26]. The advantages of UF in [13,[27][28][29][30][31][32][33].…”