Insight into membrane fouling and purification performance of aquaculture wastewater using combined microalgae and dynamic membrane

This study investigated the purification and membrane filtration performance of aquaculture wastewater by diatomite dynamic membrane (DDM) and Chlorella pyrenoidosa under the conditions and presence of heavy metal zinc, and the membrane fouling mechanism was also examined by the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. The results indicated that low zinc (< 1 mg/L) in aquaculture wastewater promoted the algal biomass, protein content, and macromolecular organics in extracellular organic matter (EOM) during algal purification process, and the filtration flux and membrane fouling induced were also the least. For the zinc of high concentration (> 0.5 mg/L), it not only produced negative effects on algal growth, the membrane fouling induced during algal harvesting was also serious. Zinc of 0.5 mg/L was more facilitated for the algae concentration effects than the other zinc treatments. DDM fouling mechanism suggested that although there exists an attractive cohesion free energy for algae under low-zinc treatment (< 1 mg/L), the filtration flux decreased gradually due to repulsive adhesion free energy between membrane and foulants as well as weak cohesion free energy between foulants and foulants. However, for algae under higher-zinc treatments (> 0.5 mg/L), the membrane fouling intensified dramatically because of both enhanced attractive adhesion free energy between membrane and foulants and increased cohesion free energy between foulants and foulants. These results had notable effects on aquaculture wastewater treatment, especially for aquaculture wastewater containing various zinc concentrations using combined microalgae and DDM.