Anion exchange as a potential method for removal of humus in drinking water treatment

Abstract

Removal of humus by anionic exchange is a potential process for small waterworks in Norway. The interaction between humic substances and a strong base anion exchange resin has been studied and the results are used for characterization of the humic substances. Thirty per cent of the organic matter were removed from the water during the first six seconds of contact with the resin. This fraction had a higher negative charge and lower molecular weight than the average for the water sample. With increasing contact time, fractions with a decreasing charge density and increasing colour and molecular weight were removed. The unabsorbed DOC fraction had a net positive charge. The anion exchange process results in a reduction in pH, and dissolved iron and aluminium are transformed from organic complexes to inorganic species. This may represent an obstacle for the practical use of the process.