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How Does SDI Work?

​What is Deionization?

Deionization: The removal of all ionized minerals and salts (both organic and inorganic) from a solution by ion exchange. Positively charged ions are removed by a cation exchange resin in exchange for a chemically equivalent amount of hydrogen ions. Negatively charged ions are removed by anion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions introduced in this process unite to form water molecules. The term deionization is often used interchangeably with demineralization. Learn more about Deionized Water.

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Evoqua doesn't regenerate your resin on-site, but at one of our nearby North American resin regeneration plants. 

 
What is Service Deionization (SDI)?

Service deionization (SDI) is a cost effective solution for producing high purity water without your investment in an on-site regeneration system.

What types of resin does Evoqua carry?

Activated Carbon
These units remove chlorine, chloramines, and dissolved organic contaminants. Each replacement carbon unit contains specially selected carbon to assure maximum water quality and service life.

 
Cation Deionizers
Cation resins remove positively charged dissolved ionic contaminants such as calcium, sodium, magnesium, potassium, iron, and manganese. The cation resins used are very durable to provide stability against osmotic, thermal, and impact shock.

 
Anion Deionizers
Anion resins remove negatively charged dissolved ionic contaminants such as carbonate, bicarbonates, sulfates, chlorides, nitrates, and silica. The anion resins used offer stability against osmotic, thermal, and impact shock. A variety of anion resins are available and suitable for any water application.

 
Premium Mixed Bed Deionizers
For higher quality water with a more neutral pH than separate bed systems, as well as enhanced silica and CO2 removal, mixed bed deionizers are recommended. Evoqua's service deionization produces the quality of water required for any application, up to 18.2 megohm-cm resistivity at 77°F (25°C). In-line quality monitors immediately alert users when resin tanks need to be changed.

 
Scavenging Resins
With extra-large internal surface areas, the microporous scavenging resins provide high adsorption of dissolved and undissolved organic contaminants. The colloidal scavenging resins remove inorganic and organic anions. Both types of resins are extremely resistant to organic fouling.

 
What are the components in an Evoqua Service Deionization (SDI) system?

  • DI systems consist of activated carbon and ion exchange resin contained in portable tanks connected directly to your tap water supply.
  • Evoqua doesn't regenerate your resin on-site but at one of our nearby North American resin regeneration plants.
  • Service deionization (SDI) is a cost effective solution for producing high purity water without your investment in an on-site regeneration system.

 
A simple system that can be rapidly expanded:

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Water comes into the system through an influent filter to remove large particles and is then cycled to a pressure regulator to ensure that the tanks are not over-pressurized. A water meter measures the volume of water produced by the system.

 
Water then flows through a portable tank of activated carbon to remove organics and free chlorine. Next it flows through two mixed bed ion exchange resin tanks. These tanks are set up in a lead / lag configuration and the first tank is often called the worker tank and the second tank is called a standby tank. Finally the high purity water flows through a very fine post filter and is then directed to use in your plant.

 
Using a lead / lag tank arrangement provides a safety tank when the first tank is exhausted and also reduces your operating cost because the tank does not have to be removed before it reaches exhaustion.

 
We offer a wide range of systems and resin types for general manufacturing and industrial rinsing, as well as special grades of resin for critical applications such as food and beverage, healthcare, biopharmaceutical, and microelectronics.

 
A more complex system that minimizes your water production cost is shown below:​

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In this system configuration, the two mixed bed ion exchange tanks are preceded by separate bed anion and cation beds. Although this configuration will take up more floor space, it does reduce the overall operating cost and should be used when you need to produce high volumes of deionized water.

 
There are many other configurations available and a system can be customized for your particular space, volume, and quality needs. 

 
What happens when my lead tank, my worker tank, is exhausted?

When the resins in the tanks exhaust, our local service representatives remove and replace the tanks with freshly regenerated tanks. You have a constant supply of high-purity water.

 
We offer a wide range of systems and resin types for general manufacturing and industrial rinsing, as well as special grades of resin for critical applications such as food and beverage, healthcare, biopharmaceutical, and microelectronics. 

 
We understand how critical it is to have a reliable and continuous supply of high-purity water. Evoqua has been supplying companies like yours with high-quality SDI systems for years. With the largest local service network in the industry, we guarantee fast, first-rate service wherever and whenever you need it.

 
And, with our 24/7, toll-free customer service hotline and team of technical support professionals, help is just a phone call away.

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 Contact us

Our experienced staff can help your business with all your deionized water system needs. To request more information and find the best solutions for you, please contact us.

Chris Bailey
954-666-6081