Fouling control strategies for ultrafiltration of microalgae cultivated in high-rate ponds treating anaerobic effluents

Strategies to control fouling ultrafiltration membranes were investigated in the recovery of microalgal biomass from effluent of high-performance ponds treating anaerobic effluent from a UASB reactor. The membrane module used was a polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration unit, with an average pore diameter of 0.03 µm. The microalgae suspension had an average total suspended solids (TSS) concentration of 120 mg/L and consisted mainly of Chlorella sp. Various fouling control strategies were assessed, including aeration, relaxation, and backwashing. These methods resulted in average transmembrane flux rates of 68.9, 63.2 and 55.7 L/m² h, respectively. In terms of fouling potential, cake resistance (R_c) development was predominant (80%) air-assisted backwashing, necessitating the use of physical and chemical cleaning to reverse the flux. While irreversible fouling resistance was increased in the tests with aeration, both flow recovery and scale formation were reduced. In addition, the results showed that the combination of backwashing and aeration achieved higher fouling reversibility and better flow recovery.