Characterizing RO Fouling Potential of Brackish Surface Water

Abstract

The city of Rifle, Colo., forged onto the frontier of reverse osmosis (RO) technology when it undertook an initiative to desalinate its increasingly saline Colorado River supply as part of a water treatment plant upgrade. Although it is well known that RO reliably rejects dissolved solids at levels exceeding 99 percent, critical questions remain about applying RO for surface water: How efficiently will an RO process operate? What level of pretreatment is necessary? The answers are linked to the water's fouling potential. Solubility models are commonly used to anticipate and prevent inorganic scaling, and chloramines can successfully control biofouling. However, the potential for organic fouling is more challenging to assess. Although membrane filtration can provide exceptional prefiltration, it is the most expensive way to control particulate fouling. Therefore, to assess organic and particulate fouling potential, the city of Rifle conducted an RO pilot test on its treated water. The pilot test results illustrate how RO fouling can manifest itself in surface water applications.