Fouling mechanisms of submerged ultrafiltration membranes in greywater recycling

Abstract

This study examined the influence of greywater constituents on the fouling behaviour of submerged hollow fibre UF membranes during greywater treatment for recycling purposes. Experiments were carried out on a bench-scale equipment using a Zenon ZW1 module. The membrane was operated under constant flux where an increase in transmembrane pressure was used to determine the extent of fouling. Wastewater constituent variables used in this study were kaolin, cellulose, humic acid, surfactant, and calcium concentration. Results indicate that during filtration of synthetic greywater multivalent ions like calcium played an important role. Depending on concentration agglomerates of different structure and size were formed and the structure and size determined the extent of fouling and retention. It was also shown that the surfactant sodium dodecyl sulphate (SDS) may cause fouling through particle stabilisation and strongly interacts with calcium enhancing calcium retention especially in the critical micelle concentration (cmc) region. It is hypothesized that SDS competes with humic acids (HAs) for adsorption sites resulting in lower UV254nm retention. Solution chemistry and cake deposition also influence the retention and hence product water quality.