Effect of shear-stress by rotation on membrane photobioreactors and bioreactor performance for anaerobic wastewater reclamation

Integrating anaerobic processes, such as the Upflow Anaerobic Sludge Blanket (UASB) reactor, with membrane photobioreactors (MPBRs) represents a significant advance in wastewater treatment, combining effective water purification, biogas production, and the generation of recoverable biomass. Short-term and long-term experiments comparing MPBR reactors with intermittent and continuous membrane rotation were evaluated to assess their effectiveness in fouling control and nutrient recovery. These configurations were also compared with a rotative membrane bioreactor (MBR) which revealed the superior performance of MPBRs in managing membrane fouling and nutrient removal. MPBR reactors surpassed the conventional MBR in permeate quality, nutrient recovery rates referred to as NRR and PRR for nitrogen and phosphorous, respectively (MPBR-I: NRR 9.2 ± 3.2 mg/L·d and PRR 0.8 ± 0.3 mg/L·d; MPBR-II: NRR 7.9 ± 1.7 mg/L·d, PRR 0.4 ± 0.2 mg/L·d), but also biomass production, indicating great potential for bioproduct recovery applications. Moreover, the continuous rotation implemented in the MPBR led to a significant reduction in fouling by enhancing particle dispersion, mitigating the negative effects of soluble microbial products, maintaining higher critical flux values, and achieving lower hydraulic resistance, despite increased carbohydrate levels due to shear-induced stress on microalgae. Although physical cleaning methods effectively removed over 90 % of fouling, highlighting its reversible nature and benefits for membrane longevity, MPBRs required stronger chemical treatments due to persistent biofilm adhesion. Therefore, an integrated approach combining rotation and chemical cleaning could effectively address current wastewater treatment needs and providing a replicable and sustainable model, emphasizing resource recovery, waste minimization, and long-term operational efficiency. • Membrane bioreactor and photobioreactor compared for enhancing UASB effluent. • Continuous and intermittent rotation evaluated as physical membrane cleaning. • Continuous rotation improved nutrient recovery in MPBR systems. • Continuous rotation decreased membrane fouling due to particles and soluble matter.