Discussion Water purity control: Papers 17-26

Professor G.N. Walton (Imperial College) In the purification of feedwater attention is given in Paper 19 to molecular size and shape. However, ion exchange resins were being used for purification. To what extent was the material in the water ionic in character? To what extent did this material consist of, for instance, humic acids which might be largely ionic? And to what extent did it consist of neutral molecules such as terpenes which one would not expect to be removed by ion exchange membranes? If alkali were added this would promote the ionization of the humic acids.

Dr J. W. Parsons (University of Aberdeen) My experience in the chemistry of both soil organic material and disolved organic components of Loch Shurreny Dounreay water suggests that most, if not all, the material is negatively charged. This results from biological oxidization processes and the first stage of these processes is the oxidation of substituent groups to carboxyl groups. Some work that we have done, but this is not reported in this Paper, suggests that under certain conditions ferrous iron reacts with polyphenolic material to produce neutral iron complexes. We have taken steps to improve the control of the alum flocculation, in particular control of pH, to reduce the possibility of these complexes forming. It would be interesting to use either paper or gel electrophoresis to look for negative, neutral and possibly positively charged organic components in water. Positively charged components may also arise through formation of iron complexes.