Pilot scale studies on the removal of trace metal contaminations in drinking water treatment using chelating ion-exchange resins

Increasing nickel concentrations in groundwaters are causing treatment problems in some locations in Germany and other European countries. Ion exchange treatment using iminodiacetic acid resin was studied under various conditions in a pilot scale plant. Breakthrough curves show that nickel, cadmium and lead concentrations of below 100 μg/L can easily be reduced to 1% of the feed concentration. Assuming a minimum removal rate of 95% the treated volumes ranged from 75,000 bed volumes up to 195,000 bed volumes depending on flow rate and calcium concentration. The process has no impact on other chemical and microbiological water quality parameters. Ideally the feed water should be free from turbidity, iron and manganese, otherwise head loss will grow very fast because of high filtration rates and the small diameter of resin beads used in this process. Nevertheless, the ion exchange resin can be backwashed without increasing the metal concentration in the effluent. Ion exchange using iminodiacetic resins is therefore a suitable treatment process for the removal of heavy metals from drinking water.