Control of Metal Oxide Fouling in Reverse Osmosis

High levels of iron and manganese, along with large quantities of dissolved gases in the wells created concern for the viability of a conventional desalination design for the proposed City of Camarillo groundwater desalination facility. To identify viable pre-treatment process(es) for the control of metal oxide fouling in reverse osmosis, a 12-month pilot study was undertaken. The pilot study tested several pre-treatment alternatives, one of which was chlorine dioxide and filtration using dual media filters to remove both iron and manganese oxides. The results of the pilot-scale testing indicated that chlorine dioxide and filtration using dual media filters is an effective pre-treatment process for preventing metal oxide fouling in reverse osmosis. Nearly 100% of iron and approximately 70% of manganese in the well water was oxidized and removed during the pre-treatment stages, and the remaining 30% of manganese did not appear to cause fouling of the reverse osmosis membranes. Chlorine resistant membranes were also tested along with standard brackish water membranes, during the pilot study. The test results indicated that standard brackish water membranes experienced damage from either the chlorine dioxide or low levels of impurities within the chlorine dioxide. No damage was seen, however, for the chlorine resistant membranes.