Pre-coagulation with cationic flocculant-composited titanium xerogel coagulant for alleviating subsequent ultrafiltration membrane fouling by algae-related pollutants

Membrane Fouling in Algal Separation Processes: A Review of Influencing Factors and Mechanisms

“…The pH-dependent surface charges exert a direct effect on the floc properties and coagulation efficiency (Zhou et al, 2014;Xu et al, 2021). As reported by Zhou et al (2014), the low pH intensifies the interactions between the EOM and the membrane surface, thus increasing the membrane fouling.…”

“…Contradictory results on the impact of carbohydrates and proteins suggest that their effect on membrane fouling is species dependent and relies on the algal growth conditions. Bin et al (2017) and Xu et al (2021) both report the stronger impact of IOM on flux decline (Zhang et al, 2016;Bin et al, 2017), while Low et al (2016) and Novoa et al (2020) report a stronger impact of carbohydrates on membrane fouling. However, all the studies highlighted the stronger tendency of EOM to irreversibly deposit onto the membrane surface (Luo et al, 2019).…”

“…As reported by Zhou et al (2014), the low pH intensifies the interactions between the EOM and the membrane surface, thus increasing the membrane fouling. Analogously, Xu et al (2021) evaluated the impact of pH on coagulation; the results highlighted the effect of the pH on the isoelectric point (pH iep ) of different coagulants, impacting the floc size and formation rate and, subsequently, the cake layer filterability. Acidic conditions favored the isoelectric point of a titanium xerogel coagulant, enabling the aggregation of algae and organic matter upon dosing; alkaline conditions, on the other hand, proved to be inadequate for achieving charge neutrality, and, thereby, the aggregation was lower.…”

“…The first group of algal fouling control strategies attempted to modify the filterability properties of algal foulants present in the feed solution, using pretreatment methods and controls in operation. Feed pretreatment relies on the use of coagulants and adsorbents to promote the formation of cells and AOM aggregates that, in turn, are easily removed from the membrane surface and show better filterability properties upon attachment (Huang et al, 2019;Xing et al, 2019;Zhang Y. et al, 2020;Xu et al, 2021). Alternatively, oxidants are increasingly used in pretreatment to reduce and mineralize the concentration of the smaller organics fraction responsible for irreversible fouling (Liu et al, 2018;Lee et al, 2019Lee et al, , 2021Wan et al, 2019;Ren et al, 2020).…”

Membrane-Based Harvesting Processes for Microalgae and Their Valuable-Related Molecules: A Review

“…However, the harvesting of microalgae using membrane-based technologies requires a relatively high-energy input which, together with fouling, constitutes the major bottleneck for large-scale applications [ 28 , 37 ]. Membrane fouling caused by blocking, cake formation and/or the adsorption of gel-foulants such as extra- and intracellular organic matter (e.g., proteins, polysaccharides, lipids and humic-like substances) negatively affects the membrane flux, increases maintenance and operating costs, and prevents efficient long-term use [ 29 , 36 , 38 ]. Therefore, the major goals in membrane-based microalgae harvesting processes are to reduce costs by mitigating fouling; thus, increasing membrane flux and energy consumption efficiency.…”