The role of zinc in physical water treatment for prevention of scale

M.Sc.Dissolved salts, mainly carbonates and sulphates such as those of calcium and magnesium, form hard water, which when heated produces an insoluble precipitate of scale forming crystals. Scale formation affects performance in industry and ouseholds. Besides the problem of energy costs, there are all the additional problems and maintenance costs of scale removal. Traditional methods of combatting scale build-up based on chemical water treatment do exist. These include: the addition of strong acid to remove the bicarbonate ion from the water, the use of chemicals to prevent or retard the formation of hard scale and, other techniques such as ion exchange process. A cost-effective alternative to these methods is Physical Water Treatment (PWT). Many different types of equipment claiming to treat water physically, for scale reduction are commercially available. These include magnetic, electric (high frequency or radio frequency) or electrostatic, catalytic and ultrasonic devices. In this work attempts have been made to unravel the mechanisms involved in PWT. For this it was necessary to develop experimental methods to determine the effect of electromagnetic fields and selected magnetic and radio frequency (rf) water treatment devices on precipitation reactions. The most significant finding of this study involves the effect of Zn on scale formation. When supersaturated Ca(HCO3 )2 solutions were tested in a glass heat exchanger, a 77% reduction in the formation of scale was found when the solutions were spiked with Zn