The conversion of seawater to potable water is called desalination. The two primary forms of desalination are distillation and reverse osmosis. Both methods are used throughout the world and technologies are improving to lower the costs of production. At Cayman Water, we currently only use the reverse osmosis method as this is the most cost efficient solution for our markets.
Reverse osmosis is a fluid separation process in which the saline water is pressurized, and fresh water is separated from the saline by passing through a semi-permeable membrane that rejects the salts. The saline (or seawater) water is first passed through a pre-treatment system, which generally consists of fine filtration and the addition of treatment chemicals if required.
Pre-treatment removes suspended solids and organics that could cause fouling of the membrane surface. Next, a high-pressure pump pressurizes the saline water thus enabling a 40% conversion of the saline water to fresh water as it passes through the membrane. Approximately 99% of the dissolved salts are rejected and remain in the concentrated saline water. This remaining feed water, which has now been concentrated, is discharged without passing through the membrane. The remaining hydraulic energy in the concentrated feed water is transferred to the initial saline feed water, with an energy recovery device thus reducing the total energy requirement for the reverse osmosis system.
The final step is post-treatment, which consists of stabilizing the produced fresh water, removing undesirable dissolved gases and adjusting the pH and chlorination to prepare it for distribution.
The equipment at our plants is among the most energy efficient available and we aggressively monitor and maintain our equipment. As a result of our years of experience in seawater desalination, we believe that we have expertise in the development and operation of desalination plants that is easily transferable to locations outside of our current operating areas.
All materials, parts and supplies essential to our business operations can normally be obtained from multiple sources. We do not directly manufacture any parts or components for equipment essential to our business.
Our access to seawater for processing into potable water is granted through our licenses and contract with the Cayman Island government.