Removal of copper and copper-binding organic ligands during potable water treatment

The concentrations and chemical speciation of copper before and after potable water treatment have been examined using 3 techniques: a copper ion-selective electrode (Cu-ISE), chemiluminescence (CL) and anodic stripping voltammetry (ASV), together with water quality parameters colour, turbidity and dissolved organic carbon (DOC). As expected, only a small fraction of colour (6.6-11%), turbidity (6.7-14%) and DOC (20%) remained after treatment. The removal of Cu and Cu-binding natural organic matter (NOM) was more variable but still significant: 17-64% of total dissolved Cu and 19-61% of Cu-binding NOM (as determined by ASV) remained after treatment. Labile Cu levels, as measured by CL, were 0-23% after treatment. The Cu-ISE titrations showed significant Cu-binding in raw water in the concentration range 10(-7) to 10(-6) mol l(-1) Cu2+, but very little binding after treatment. The results indicate that conventional water treatment has a significant effect on both total Cu levels and Cu-binding NOM, with implications for Cu2+ speciation and bio-availability, particularly in reticulation systems containing copper pipes.