EDI (Electro Deionised) Ultra Pure Water (UPW)

Deionization (or demineralization) simply means the removal of ions. Ions are electrically charged atoms or molecules found in water that have either a net negative or positive charge. For many applications using water as a rinse or ingredient, these ions are impurities and must be removed from the water.

Ions with a positive charge are called Cations and ions with a negative charge are Anions. Ion exchange resins are used to exchange non-desirable cations and anions with hydrogen and hydroxyl, respectively, forming pure water (H2O).

EDI Reverse Osmosis Plant - Electro Deionization (Edi System)

A water treatment technology that is electrically driven and used, ion exchange membranes, electricity, and resins to purify water by removing ionized species.

Working of EDI Reverse Osmosis

EDI Reverse Osmosis Plant consists of chambers that contain ion exchange resins and are separated by ion-exchange membranes. When water enters the modules, an electrical field at right angles is applied to the flow that forces ions to move through resins and across membranes. The impurities are not bound to a media and are collected in a concentrated stream which is either directed to the drain r recycled.

EDI System

EDI Reverse Osmosis Plant Advantages

What is pharma grade water?

In pharmaceutical production, the water used in processing, sanitizing and as a feedstock in medicines (IV FLUIDS) must meet the strict criteria on purity standards. That water typically known as pharma grade water, with around 0 to 1 ppm TDS. Different grades of water quality are used which depends upon the end use either water is used as a medium or can be used in the manufacturing process during synthesis, as a cleaning agent or during the production of finished product. As per client’s request, two types of water are used in pharmaceutical production:

Highly Purified
Water for Injection

Major techniques to produce pharma grade water

In pharmaceutical Industries, three types of techniques are used in the form of filtration systems to produce pharma grade water:

ION Exchange Water Filtration Systems: The deplorable water-soluble ions are exchanging with the desirable ones in this system and ionic composition of water is adjust in a desirable direction.

Reverse Osmosis Plant Process: In this technique, the natural osmotic flow of water is disturbed by applying pressure to the concentration solution in an osmosis process. This results in the flow of water from a more concentrated to a less concentrated solution.

Distillation Technique: This is the extensively used technique in pharmaceutical practice. But the most used technique for bigger quantity is RO followed by EDI.

How pharma grade water was being produced through water distillation process?

In order to produce pharma grade water through distillation process, at first 10 to 20 percent of the condensate should be removed since the supply water comprises a large amount of harmful chemicals, later on, the final 20% should be eliminated as well to avoid extra amount of dryness which can result in the contamination of previous distillate by solid impurities. A liquid mixture containing volatile components is boiled by heat and then vapor is recovered with the help of condensation.

In sum, an EDI system can consistently and predictably remove dissolved materials such as salts, acids and bases, especially weakly ionized materials such as low molecular organics, carbon dioxide, silica, and boron. The continuous regeneration process also eliminates pH shock and greatly extends the life of the resins.

When this localized voltage potential exceeds approximately eight tenths of a volt, an electrochemical reaction occurs and water molecules are split into H+ and OH– ions, which are essentially acid and caustic. The acid and caustic generated in the module regenerate resin beads by replacing other trace ions remaining the attachment of H+ and OH- ions. This is exactly what happens to resin beads when acid and caustic are used for regeneration in conventional deionization systems.

As a result, an EDI system does not need chemicals for regeneration. The electric potential does all the work. You essentially have a worker and a polisher combined into one unit which constantly regenerates.

Applications

EDI water (Type II water) is often selected for projects requiring ultra-high purity water, typically used in the following fields:

Laboratories
Pharmaceuticals
Power generation

Boiler feed water
Semiconductor production

Electronics & Microelectronics
Food and Beverage

Benefits

Removes dissolved inorganics/low molecular organics effectively

A constant flow of Type II water. Reliable and consistent water quality.
Resistivity: 5-16MΩ • cm @ 25 °C， typically >15MΩ • cm
TOC < 30 ppb

Reliable and consistent water quality

Produce a constant flow of Type II water

Environmentally friendly

No chemical regeneration.
No chemical disposal.
No resin disposal.
Low energy consumption.

Inexpensive Operation Cost:

No need for neutralization units
No need for local permitting
No need for other costs of chemical
Low power consumption

Low Maintenance Needs

Long life-cycle because of continuous regeneration of the ion exchange resins inside the module (little exhaustion)

Safe Operation

No hazardous chemical is required
Less risk to people and accidental discharge
No heating element

What is a Deionized Water System?

A deionized water treatment system is an arrangement of DI tanks and other components that are used to produce high purity water. The DI tanks are typically made of fiberglass and come in various sizes to accommodate different feed flow rates. A deionized water system can be as simple as a one tank setup or as complex as a multi-tank system with supporting equipment such as reverse osmosis, ultraviolet (UV) disinfection and elaborate water quality monitoring equipment. DI tanks contain ion exchange resin which selectively remove ions from water.

Eventually the DI tanks need to be replaced by the service provider and replaced with a fresh tank. Many customers require standby DI tanks onsite to make sure they have an uninterrupted flow of deionized water. The DI tank exchange frequency depends on the incoming water quality and the amount of water being used. The higher ionic load in the incoming feed water will result in less gallonage produced by the DI tank.

A DI water system is a convenient and clean solution for producing deionized water because Puretec handles all the equipment, off site regeneration, hazardous chemical handling, maintenance, and emergency repairs for the deionized water system.

Oftentimes a DI system is used with, or in place of, reverse osmosis systems. DI can be used in conjunction with a reverse osmosis system to produce reliable high quality deionized water. The RO system will remove a bulk of dissolved solids (90% to 99%) before entering the DI tank which will then remove any remaining ions in the water. Placing an RO before DI tanks will allow you to get a much longer run length from your DI tanks and reduce cost. However, an RO system requires a much larger upfront investment, constant maintenance, and the ability to discharge brine waste from the RO unit which must be considered when choosing a DI system.

How does ion exchange work?

Ion exchange resins are used to produce deionized (demineralized or DI) water. These resins are small plastic beads composed of organic polymer chains that have charged functional groups built into the resin bead. Each functional group has either a fixed positive or negative charge.

Cation resin has a negative functional group and attracts positively charged ions.

There are two types of cation resins – weak acid cation (WAC) and strong acid cation (SAC). Weak acid cation resin is used mainly in dealkalization and other unique applications. This paper focuses on explaining the role of strong acid cation resins used for producing deionized water.

Anion resin has a positive functional group and attracts negatively charged ions.

There are two types of anion resins – weak base anion (WBA) and strong base anion (SBA). Both types are used to produce deionized water, however, they have different characteristics.

WBA resins do not remove silica, CO2 or neutralize weak acids and have a lower than neutral pH when used in a dual separate bed system.

SBA resins remove all anions in the above table, including CO2, and have a higher than neutral pH when used in a dual separate bed system due to sodium leakage.

Mixed bed resins use SAC and SBA resins combined.

To produce deionized water, cation resin is regenerated with Hydrochloric Acid (HCL). The Hydrogen (H+) is positively charged and attaches itself to the negatively charged cation resin bead. The anion resin is regenerated with sodium hydroxide (NaOH). Hydroxyl (OH-) is negatively charged and attaches itself to the positively charged anion resin bead.

Different ions are attracted to a resin bead with different strengths. For example, calcium is more strongly attracted to a cation resin bead than sodium would be. The hydrogen on the cation resin bead and the hydroxyl on the anion resin bead do not have a strong attraction to the bead. This is what allows ion exchange to take place.

Different type of ion exchange resins used in water treatment

EDI (Electro Deionization) System - Water & Waste Water Related Solution