Development of an integrated iron oxide adsorption/membrane separation system for water treatment

The performance of an integrated iron oxide particle (IOPs) adsorption and ultrafiltration (UF) process was investigated in terms of natural organic matter removal and membrane permeability during treatment of a drinking water source. Throughout the fractionation of raw water and subsequent UF of fractioned portions, the significance of each component in raw water affecting flux decline during IOP-UF was evaluated. Natural organic matter (NOM) removal efficiencies for the IOP-UF system increased markedly as a substantial amount of IOPs was added into suspension, without any negative effect on permeate flux. During IOP-UF testings, there was no difference in NOM removal regardless of the locations of IOPs whether they were either in suspension or deposited on the UF membrane, but significant initial flux reduction occurred with the formation of a precoat (attached) layer. However, all IOPs in suspension and in the cake were effective in both removing NOM and preventing irreversible fouling as long as they were removed by backwashing. Dissolved matter obtained from filtration through a 0.45 μm filter was more responsible for flux decline in UF than larger colloids. Particularly, IOP-adsorbable dissolved matter accounted for 60% of total flux decline, confirming the attractiveness of IOP addition to UF.