Iron oxide-coated media for NOM sorption and particulate filtration

This study applied newly developed iron oxide-coated media (IOCM) to the removal of natural organic matter. (NOM) and particulate filtration in drinking water treatment. The sorption capacity of IOCM for NOM directly depends on the amount of iron retained on the media surfaces and generally increases with the decrease of solution pH, the increase of empty bed contact time, and the concentration of Ca2+. Using olivine as the supporting medium significantly improved the performance of IOCM at neutral pH. Although the sorption capacity of IOCM is limited by the amount of oxides that can be coated on the media surfaces (about 5 percent by weight), results from the pilot studies indicated the frequent regeneration of the media (twice a week) can effectively maintain system performance at the desired level. The NOM-laden IOCM was nearly completely regenerated using 3 bed volumes of 0.5 N sodium hydroxide solution, and NOM concentration in the regenerant was as high as 4,300 mg/L DOC. The sorption capacity of IOCM deteriorated mildly in a long-term test, possibly because of loss of iron during the backwash cycles. Results from both bench tests and pilot studies also showed that IOCM outperformed regular sand in particulate filtration in terms of head loss buildup and turbidity breakthrough.