| A new test to predict the fouling potential of a reverse osmosis (RO) feedwater was developed. The Permanganate Demand Test is based on both of the accepted equations used to describe the solvent and solute flow through the membrane. It characterizes the reduction in solvent flow by an increase in the osmotic pressure at the membrane.; The Silt Density Index (SDI) is a membrane test that has come into widespread use to predict the fouling potential of a feedwater. RO processes can be expected to operate successfully over a long period of time without significant reduction in permeate flux if the SDI values are between 2 and 5.3, on a scale of 1 to 6.67. The study of the SDI was conducted as a step-off point to a subsequent study of fouling, and the development of the Permanganate Demand Test.; The SDI was found to be sensitive to suspended particles large enough to be measured as turbidity, but insensitive to dissolved metal concentrations. The concentration of humic acid in the feedwater, that would result in acceptable SDI values, was found to be between 0.5 and 1.0 mg/l.; The fouling potential of humic acid feedwater solutions to a RO membrane was studied, as humic substances account for over 90% of the organics in natural waters. The rate of fouling was found to be directly related to the concentration of humics in the feedwater.; The Permanganate Demand Test was developed to characterize the concentration of humics by a simple procedure that could be performed in a few hours by plant operation personnel. Since the test successfully represents the humic concentration, and the concentration of humics relates to the rate of fouling, a predictive equation could be developed. This equation predicts the permeate flux decline from the permanganate demand of the feedwater.; The test was performed on a saline feedwater containing iron, which was reported as a major cause of fouling in the literature. The iron, in the form of ferrous ammonium sulfate, did not have a permanganate demand, and no fouling occurred in a month long trial. |
