Dewatering of Chlorella pyrenoidosa using a diatomite dynamic membrane: Characteristics of a long-term operation

Microalgae harvesting has been a primary problem encountered during microalgae utilization because of the low biomass concentration of microalgae and the severe membrane fouling caused by extracellular organic matters (EOM). Our previous study verified the applicability of dynamic membrane technology for algae dewatering. The aims of this study are to investigate the performances of both the diatomite dynamic membrane (DDM) technology, used for algae dewatering during a long-term (96 h) operation period, and the membrane fouling mechanisms, as well as their relationship with algae growth phases. The stable filtration flux reached 12.8 L/m2 h, and the ultimate biomass concentration reached 49 g/L. The DDM continued to have advantages in cost, energy consumption and ultimate algae concentration. However, the stability of the DDM was questionable for long-term operations. Algae growth phases had distinct impacts on the EOM concentrations and composition and, therefore, on the membrane fouling mechanisms. The osmotic pressure originating from the EOM might exist during the DDM filtration process and could be largely responsible for the high cake resistance. As the algae growth phase advanced from the logarithmic phase to the decline phase, membrane fouling became much more severe.