Algal fouling of microfiltration and ultrafiltration membranes and control strategies: A review

Microalgae are ubiquitous in aquatic systems and are a highly diversified group of uni- and multicellular microorganisms. In low pressure-driven membrane systems, these cells and their secretions have a strong tendency to foul membranes and lead to a very low filtration efficiency. A significant amount of investigation on algal fouling of microfiltration (MF) and ultrafiltration (UF) membranes has been conducted in recent years. In this paper, recent knowledge of both MF and UF membrane fouling by microalgal suspensions, including the mechanisms and factors influencing algal fouling control strategies, is reviewed. The main components and properties of microalgae suspension are summarized. As algal cells and algogenic organic matter (AOM) are major foulants in microalgae suspension, their roles in algal fouling are compared and critically assessed. Based on the fouling mechanisms of these cells and AOM, strategies for mitigation of algal fouling are provided in detail, including pretreating feedwater, changing membrane properties, and enhancing hydrodynamic conditions. The breakup and growth of cells and their consequential influences on fouling receive special attention. Finally, useful directions for further work on MF and UF algal fouling are indicated.