Electro De-Ionization (EDI) is a water purification technology that combines ion exchange resin, ion-selective membrane, and electric current to continuously reduce dissolved ion content.
This technology is generally used after the Reverse Osmosis (RO) process as a polishing stage to produce water with a high level of purity without the need for periodic chemical regeneration as in conventional Mixed Bed systems.
Hydromaster provides EDI systems that can be integrated with a range of industrial water treatment plants based on feed water quality, capacity, product water quality targets, and project operational needs.
What is Electro De-Ionization (EDI)?
EDI is a continuous deionization process that utilizes a combination of ion exchange resins, ion selective membranes, and electric fields.
Ions dissolved in water are directed through the membrane towards the concentrate stream, while water with a lower ion content exits as product water.
Because the resin is continuously regenerated through an electrochemical process, the EDI system does not require regeneration using acids and bases as is commonly used in conventional Mixed Beds.
Ion exchange in the EDI system is continuously generated, unlike resin-based demineralization systems. Typically, product water resistivity of >15 MΩ.cm is consistently achieved using this process. In addition to the advantages of practical operation and reduced downtime during regeneration, EDI can also provide more consistent product purity levels than resin-type ion exchange systems.
How Does the EDI System Work?
The EDI system receives feed water of a certain quality, generally from Reverse Osmosis.
Within the EDI stack there are:
- Ion exchange resin
- Cation exchange membrane
- Anion exchange membrane
- Electrode
- Product water channel
- Concentrate water channel
When an electric current is passed, positive and negative ions move towards opposite electrodes through an ion-selective membrane.
The ions are then channeled to the concentrate stream, while the main stream produces water with a higher level of purity.
In general, the system configuration can be:
Pretreatment → Reverse Osmosis → EDI → High-Purity Water
The actual configuration needs to be adjusted to the feed water quality and product water target.
Advantages of EDI technology over Mixed Bed Deionization:
- No chemical for regeneration required
- Much lower downtime - proven technology
- Guaranteed consistent output quality and flow
- Reduced health and environmental risks
- Less footprint
- Lower operational costs in terms of chemicals and labor cost
- Continuous process, not batch process
Disadvantages of the EDI system over Mixed Bed Deionization:
- Stricter input quality criteria
- Relatively higher initial investment costs, but with a short payback period due to its low operational cost
How does EDI produce such pure water?
Diagram 1
Diagram 2
EDI vs Mixed Bed Demineralization
Both EDI and Mixed Bed are used to produce water with high purity levels, but their operating principles are different.
Electro De-Ionization (EDI)
- Using resin, membrane, and electric current
- Operating continuously
- Does not require periodic acid and base regeneration
- Requires feed water with more controlled quality
- Generally placed after Reverse Osmosis
Mixed Bed
- Using cation and anion resins
- Requires periodic resin regeneration
- More flexible to various feed water conditions
- Requires the use of regeneration chemicals
- Widely used as polishing demineralized water
Technology selection needs to consider the target water quality, feed water, capacity, operational costs, and needs of each project.
EDI Applications for Industrial Needs
EDI is suitable for use in facilities that require consistently high-purity water, including:
- Power plant
- Boiler feed water
- Electronics industry
- Pharmaceutical industry
- Chemical industry
- Manufacturing industry
- Process water
- High-purity utility water
- Demineralization plant
The water quality requirements of each industry are different, so the system design needs to be determined based on the actual specifications of the project.
EDI Integration in Demineralization System
EDI is generally not a standalone technology.
To obtain optimal performance, the system can be integrated with several water treatment technologies such as:
- Multi Media Filter
- Ultra Filtration
- Brackish Water Reverse Osmosis
- Reverse Osmosis
- Demineralization System
- Mixed Bed as an alternative or additional polishing in certain applications
One example configuration could be:
Raw Water → MMF → UF → RO → EDI → Product Water
The final configuration needs to be adjusted based on the raw water characteristics and water quality targets.
Hydromaster Experience on RO + EDI Systems
Hydromaster lists Electro De-Ionization (EDI) as part of its water treatment technology in its company profile.
One of the project references listed is:
Pesanggaran Gas Power Plant – Bali
System: Demineralization System (RO + EDI)
Capacity: 12 m³/day
Year: 2022
This reference shows the application of Reverse Osmosis and EDI integration for demineralized water needs in the power generation sector.
Why Choose Hydromaster?
Hydromaster has been providing water and wastewater treatment solutions in Indonesia since 2005.
The Hydromaster approach includes:
- Problem Identification
- Engineering Design for
- Fabrication & Procurement
- Construction & Installation
- Commissioning
- Operator Training
- Operation & Maintenance
- DBOO / DBOT for specific applications
With this approach, the EDI system can be designed as part of the overall water treatment process, rather than simply selecting units based on capacity.
Frequently Asked Questions about EDI
What is Electro De-Ionization (EDI)?
EDI is a continuous deionization technology that uses ion exchange resin, ion-selective membrane, and electrical energy to remove dissolved ions from water.
Does EDI require Reverse Osmosis?
In many applications, EDI is used after Reverse Osmosis because it requires feed water with relatively high and controlled quality.
What is the difference between EDI and Mixed Bed?
EDI operates continuously without periodic chemical regeneration, whereas Mixed Bed uses resin that needs to be regenerated using chemicals.
Does EDI use regeneration chemicals?
EDI does not require regular regeneration using acids and bases like conventional Mixed Bed.
What industries use EDI?
EDI is widely used for power plants, boiler feed water, manufacturing, pharmaceuticals, electronics, and other industries that require high-purity water.
Does Hydromaster have experience with EDI systems?
Yes. Hydromaster's company profile lists the RO + EDI Demineralization System project at the Pesanggaran Gas Power Plant in Bali in 2022.
Need an EDI System for High-Purity Water?
Consult on feed water quality, capacity, and product water quality targets together. Hydromaster to determine the RO + EDI configuration that suits your industry needs.