Examining the effect of ionic constituents on crystallization fouling on heat transfer surfaces

The effect of the most abundant constituents in potable water on fouling of aluminium surface has been studied systematically in this work. The role of sodium, chloride, magnesium and sulphate ions and total organic carbon (TOC) on the fouling kinetics and morphology was assessed using a once-through open flow cell. The findings showed that the fouling resistance to heat transfer increases with the concentration of chloride and sodium. A complex influence of magnesium was found on the scaling process, varying between inhibition and promotion of scale formation depending on the concentration. At high concentrations of Mg2+, the formed scale layer consists of needle-like aragonite coated by a crust of magnesium deposits. The inhibitory performance of sulphate SO42− was found to be insignificant when compared with Mg2+ under similar conditions. Even though it is undesirable in potable water, inhibition efficiencies of TOC were 31.3% and 47.9% at concentrations of 2 and 4.3 mg/L respectively. The morphology observations illustrated that the presence of TOC produces a rough scale layer.