Measurement of polymer residuals in an alum sludge

Polymer residuals in the supernatant derived from an alum sludge following conditioning were measured by size exclusion chromatography. The method was developed on a commercial nonionic polyacrylamide, Flocmiser 50. The sludge arose from the treatment of highly coloured upland water. Chromatography was carried out in a high performance liquid chromatography unit with UV detection, initially with nanopure water as mobile phase. The column was a PL Aquagel-OH 40 based on a rigid 8 um macroporous gel. Further work demonstrated that 0.8 M sodium sulphate was a superior mobile phase with the detector set at 202.6 nm. The method proved suitable for cationic and anionic polymers. It had potential for optimizing polymer dose. The example studied in detail showed that the polymer-sludge interaction was characterized by an apparent adsorption isotherm.