Effects of Fe3+ on EPS secretion and membrane fouling of microalgae-bacteria symbionts for breeding wastewater treatment

By cultivating microalgae-bacteria consortia in breeding wastewater with varying concentrations of Fe3+, this study investigated the impact of Fe3+ on the secretion of extracellular polymeric substances(EPS) by the consortia. The extracted EPS components were fractionated, and membrane fouling tests were conducted to examine the changes in membrane fouling characteristics by the microalgae-bacteria mixed liquor and each component. The experimental results indicated that the addition of Fe3+ effectively mitigated membrane fouling, with the least fouling observed at iron mass concentration of 150 mg/L. The Hermia classic model was used to fit and analyze the membrane flux attenuation process. The results showed that the formation of the filter cake layer was one of the main causes of membrane fouling. In addition, an increase of Fe3+ would cause changes in the particle size of microbial flocs, which would have a significant impact on membrane fouling. Analysis of the membrane surface foulants showed that the main components were tryptophan-like proteins, tyrosine-like proteins, and microbial metabolic by-products.