Fouling mechanism identification and analysis in microfiltration of laundry wastewater

Microfiltration (MF) is known as a promising and green technique that can effectively treat domestic and industrial wastewaters. Inevitably, membrane fouling and scaling hinder productivity and large-scale implementation of this process. The aim of the present study is to evaluate the membrane fouling and flux decline behavior during laundry wastewater treatment. The filtration tests were performed using real domestic laundry wastewater at different transmembrane pressures (0.5-1.5 bar) and feed flowrates (30-80 L/h). Several fouling models including the single and multistage Hermia models were fitted to experimental data. The results of the single-stage Hermia model showed that the cake layer formation (with R-2 greater than 0.94) was the main contributor to the flux decline regardless of the operating condition. Results also revealed that by increasing the feed pressure, the contribution of the cake formation mechanism enhanced while an opposite behavior was observed when the feed flow rate increased. However, the single stage model could not accurately predict the performance during the entire filtration time. A more detailed analysis indicated that at least a three-stage model (complete pore blocking in early stage, intermediate pore blocking in middle stage, and cake formation in final stage) could model the flux decline during the entire filtration time with acceptable accuracy (with R-2 greater than 0.96). Therefore, the multistage Hermia model was used for determining either fouling mechanism, ways for postponing fouling of the membranes, and flux decline behavior during the membrane filtration of laundry wastewater experiments.