Experiences from operation and regeneration of an anionic exchanger for natural organic matter (NOM) removal

Anionic exchange is an alternative to traditional drinking water purificati on processes when the main problem is a high concentration of natural organ ic matter (NOM) in the raw water. A few treatment plants employing anionic exchange have recently been installed in Norway. Some. of these have after some time experienced increasing colour of the processed water. In the pres ent study we show that the resin selectively adsorbs fulvic acid from the w ater while colloidal aggregates of humic substances and iron, which also co ntributes to the water colour, are nearly unaffected by the treatment. The treatment efficiency is successively reduced as the resin becomes fouled wi th iron from the raw water. Resin cleaning with hydrochloric acid had littl e effect, while treatment with a sodium dithionite solution resulted in ful l recovery of the treatment efficiency. (C) 1999 IAWQ Published by Elsevier Science Ltd. AU rights reserved.