The Degradation of Polyelectrolytes in the Environment: Insights Provided by Size Exclusion Chromatography Measurements

Using a recently developed method for analysing high molecular weight polyelectrolytes by size exclusion chromatography (SEC), the degradation due to ageing, ozone, chlorine, and biological processes, of a commercially available cationic polyelectrolyte, was investigated. These polyelectrolytes are widely used in water and wastewater treatment, and residuals discharged into drinking water or into natural water bodies could be subjected to one or more of the above-mentioned degradation processes.

In general, degradation rate increased with decreasing concentration, increasing pH, and increasing temperature. SEC measurements showed that complete degradation (ie to CO₂ and other inorganic monomers) occurred only during biodegradation. Ozonation and chlorination increased degradation rates, but also produced refractory compounds. Acrylamide, one of the starting monomers of the copolymer used, was not produced during degradation, and in fact decreased in concentration during all the degradation mechanisms studied. On the other hand, chloroform was produced as a result of interaction with chlorine. At pH 9, the mass produced, 58 µg/mg polyelectrolyte, could result in substandard drinking waters if significant residual concentrations of this polyelectrolyte were chlorinated.