Effects of Salinity on the Rate of Aggregation of Humic Acids and Substances

Abstract

Humic substances comprise a major portion of organic matter found in natural waters, the presence of which poses issues in water treatment, as they react with chemicals used in the chlorination process, forming toxic by-products. Humic acids have the potential to disaggregate and move across a membrane, such as those used for filtration, and proceed to re-aggregate after filtration, though little is known about the process that allows re-aggregation to occur. This study focuses on how the rate of this aggregation could be affected through the variation of salinity in a humic acid-containing water sample. Each of the 15 collected pond water samples were filtered at 0.45 microns, subjected to constant shearing via a rheometer, and subsequently monitored through Dynamic Light Scattering (DLS) as the humic substances re-aggregated. The aggregation time, defined as the first appearance of a 5-micron particle, was found to have a quadratic dependence on NaCl concentration.