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Desalination plants are used where access to fresh water is limited. They provide people with potable water and industries with process water.

Filters in desalination systems protect overall system performance by removing particles, then system prefilters protect the desalination process itself. For systems in areas with airborne contaminants that could harm treated water quality, filters are used to protect the water stored in tanks.

Below is a schematic showing the filtration steps in a simplified reverse osmosis based desalination system. There are other possible treatment steps and chemical feeds that are often part of desalination systems. The chemical feeds may also use filtration, but are not included here.

Desalination System Components (simplified)

Large Particle Filtration

Most systems use a multi-media (sand) filter to remove large debris from the raw water feed. That coarse filter is followed by a depth filter to remove sediment and visible particles. These two steps protect the finer filters downstream and help to assure efficient, cost effective operation of the system.

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Particle Filtration

Raw water usually has a large load of particles of all sizes. While the multi-media and large particle filters remove most of the visible particles, there are many more small particles that can prematurely foul a reverse osmosis system prefilter or membrane. This step, performed by depth filters, will protect the downstream processes from being overloaded and plugging too soon.

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System Prefiltration

These filters are crucial to keeping the expensive reverse osmosis membranes clear of most debris and operating efficiently. Keeping the particle level low reduces the frequency of RO membrane cleaning and increases system "up time".

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Tank Vent Filters

Filters help prevent contamination of fresh water in the storage tank from dust and even bacteria. The air around tanks is full of airborne dust particles, bacteria, and other contaminants and particulates. Drawing water from a tank also draws that contaminated air into the tank.

Because the tanks used for water storage are sealed, sizing a vent filter system is critical. A filter system that causes too much restriction of the flow of air in and out of the tank can cause the tank to over-pressurize (and possibly damage seals) or be subjected to a vacuum (and potentially collapse the tank). Critical Process Filtration has years of experience sizing filter systems and can help you design your system to avoid such issues.

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Bioburden Reduction or Sterilizing Filters (optional)

The fresh water may be subjected to further treatment before use. If there is no further treatment, then system operators may choose to install a bacteria filter to assure that any bacteria that may be inadvertently introduced into the treatment system is prevented from migrating downstream.

Membrane filters with pore sizes of 0.22 µm are usually used for this application.

Bioburden ReductionSterilizing Filtration

Contact Critical Process Filtration for more information.