Removal of iron and manganese from groundwater by oxidation and microfiltration

Iron and manganese can be removed from groundwater by a process which combines oxidation and microfiltration (MF), especially when the concentrations of these metals are high and variable. The present experimental work focused on the MF of iron and manganese oxide suspensions in order to study the effects of the operating variables (tangential flow rate, pressure, metal feed concentrations) on permeate quality and permeation flux decline, i.e., membrane fouling. Artificial and natural groundwaters in which iron and manganese were previously oxidized were used to perform laboratory-scale MF experiments. The results show that the oxide particles, with sizes ranging from 1.5 to 50 mum, were efficiently microfiltered even at high concentrations. Within the experimental limits, the effect of operating pressure appeared to be much more significant than the those of tangential flow rate and feed concentration. A relatively high and constant permeation rate of 0.5 m/h was obtained at a pressure below 10 kPa, whereas rapid permeation flux declines were observed at higher pressure. Both artificial and natural groundwaters always exhibited very similar behavior.