Copper corrosion control in the Netherlands

Copper is the most commonly used material for pipes in domestic installations in the Netherlands. Depending on the composition of the water the copper pipes can add a significant amount of copper to drinking water. In the new European Drinking Water Directive (98/83/EC) the parametric value for copper in drinking water is decreased from 3 to 2 mg/l. The new directive also stipulates that copper levels should be determined on the basis of a sample ‘taken at the consumers' tap’ representative of the weekly average intake by humans. Harmonisation of monitoring protocols for copper in the European member states is necessary.

In the Netherlands about 45% of the drinking water is already softened or de-acidified in order to decrease copper concentrations in drinking water. In the Netherlands two new treatment techniques have been studied for their impact on copper release; these are Reverse Osmosis (RO) and the addition of inhibitors.

Copper pipe rig tests have shown that RO treatment decreases copper release. Split treatment of water with RO reduces copper solubility of drinking water through a decrease in both total inorganic carbon (TIC) and sulphate level. Remarkable was the relatively small decrease in copper release after split treatment with RO, compared to previous experiences in the Netherlands, suggesting an effect of natural organic matter. A new promising technique in the Netherlands is the addition of the inhibitor carbonate-activated silicate. At the test sites, the reduction in copper solubility due to the use of carbonate-activated silicate was 15 to 35%.