Inhibitory effect of Hydrex anti-scalant on calcium scale deposition from seawater under multiple-effect distillers' conditions

• The inhibition of the scale by a commercial antiscalant in MED has been studied commercial anti-scalant.
• The influence of concentration factors and dose have been investigated.
• Significant amounts of scale deposited from the seawater containing high concentrations of calcium ions.
• Percentage inhibition decreases with increasing the temperature and increases with increasing the dose.
• The percentage inhibition was almost 100% for the carbonate scale.

In this work, the inhibitory effect of a commercial anti-scalant (Veolia Hydrex® 9209) on the calcium minerals of carbonate, sulfate and hydrocalumite (Ca/Al) clay deposition from seawater has been investigated. Different concentration factors and anti-scalant doses were studied by analyzing the water hardness and turbidity. The inhibitory effect of the investigated anti-scalant was efficient even at lower concentrations. The percentage inhibition decreases with increasing the temperature and increases with increasing the dose/amount of the anti-scalant. The carbonate scale inhibition was >99% and 98–99% at 50 and 70 °C, respectively. The percentage inhibition of sulfate from hemihydrate was ranged from 80% to 87% for 2 and 8 ppm anti-scalant at 50 °C. The inhibition of Ca/Al hydrocalumite deposition increases from 70% to 90% upon increasing the dose from 3 to 5 ppm, respectively. A recommended useful dose of antiscalant for seawater is 5 ppm.