INFLUENCE OF NATURAL ORGANIC MATTER (NOM) ON COPPER CORROSION IN TAP WATER SYSTEMS / Inverkan av naturligt organiskt material på kopparkorrosion i dricksvattensystem
There are wastewater treatment plants in Uppsala municipality with both high and low copper concentrations in the sludge, this is somewhat surprising as the raw water (groundwater) often is pumped up from the same esker (gravel ridge or glacial origin), the chemical composition or the water is expected to generate strong copper corrosion, as the water is hard with high alkalinity and pH around 7,5.
A literature survey was performed to gee suggestions for parameters that can influence copper corrosion in tap water systems. A comparison was then done with data from 10 couples of water treatment plants/wastewater treatment plants from different places in the municipality. The number or data couples was later increased to 23 with data from neighbouring municilaities.
It appeared that copper content in sludge and natural organic matter (NOM) in distributed tap water had a good fit to a straight line for COD-values (COD-Mn) up to 2.5 mg/1. A reduction of the NOM-concentration can therefore be an interesting method to diminish the copper corrosion. At the same time a water is obtained which gives less biological growth in the distribution net. A lower concentration of disinfection by-products is another advantage by NOM-reduction.