Successful antiscalant field trial — Optimization at higher pH and seawater temperature — Larnaca Desalination Plant

Abstract

A desalination plant has been operating for a number of years at elevated pH both at the first and second reverse osmosis stages at feed seawater temperature up to 30°C. The main reason for operating at higher pH was to enhance the boron rejection capability of existing membranes and thus omit the operation of the second stage whenever lower seawater temperatures allow to do so and subsequently produce more water with less energy. However, a higher pH in conjunction with high seawater temperatures creates conditions for membrane scaling. Therefore an appropriate cost effective antiscalant has to be used at minimum dose level. This paper describes field trials of selecting and applying an appropriate antiscalant and the dosing optimisation process in function of feed seawater temperature and pH.

Keywords:

• Antiscalant
• Chemicals
• Scaling inhibition
• Magnesium hydroxide
• Calcium carbonate
• SWRO
• Desalination
• Reverse osmosis
• Membrane