WATER TREATMENT TECHNOLOGY

FACT SHEET

Note: Information is from vendor, however specifications may have 

changed. Contact vendor for updates. Water Treatment Catalog and Decision Tool

ELECTRODIALYSIS

Process Description

The basic principles of the electrodialysis (ED) treatment 

process are similar to ion exchange in that dissolved ions 

present in water have either a positive or negative charge 

and are attracted to electrodes with an opposite electric 

charge. ED differs from a normal ion exchange process by 

utilizing both cation and anion selective membranes to 

segregate charged ions extracted from a water solution. In 

ED, membranes that allow either cations or anions (but 

not both) to pass are placed between a pair of electrodes. 

An improvement to ED, referred to as Electrodialysis 

Reversal (EDR), utilizes the same concept except that in 

EDR, there is periodic automatic reversal of polarity and 

cell function to reverse the flow of ions across the 

membrane. This returns anions across the anionic 

membranes and helps break up scale formed on the 

concentrating face of the membranes and minimizes 

membrane fouling. As with RO, a small pump is required 

to move the water through the membranes to overcome 

the resistance of the water as it passes through the narrow 

passages.

Technical Capabilities

Depending on the number of stages present within an ED

unit, this treatment process can remove approximately 

25% to 60% TDS with a resulting stream of 

approximately 15 to 30% of the raw water input, 

although higher water recovery rates (90%) are 

obtainable with low TDS concentrations (<2,000 mg/L). 

The ED treatment process is also applicable for removing 

and/or reducing aluminum, barium, bromide, cadmium, 

calcium, chloride, 97-98% of copper, 90 to 95% of 

cyanide, 94 to 97% of potassium, and VOCs.

HEED, or High Efficiency Electrodialysis, is capable of 

purifying water to contain less than 2 ppm TDS at a 

flowrate of about 2,400 BPD. The waste generated by 

this process is less than 2% of the original contaminated 

water. To achieve these purity levels though, the original 

TDS levels must not exceed 22,000 ppm. The HEEPM, 

or High Efficiency Electro-Pressure Membrane, is an 

improvement of the HEED. It uses HEED technology in 

addition to pre-filters and RO systems. Vendor 

information indicates it is capable of handling TDS levels 

up to 50,000 ppm and with water recovery up to 99% of 

the feed water. 

Technical Limitations

Standard ED is limited to treating TDS concentrations 

ranging from 4,000 mg/L to 15,000 mg/L, although 

some newer ED technologies have reported the ability to 

treat higher TDS concentrations (approximately 35,000 

mg/L at a flow rate of 10,000 BPD with 75% recovery). 

However, as reported by Hayes and Arthur (2004), the 

economics limit the applicability of standard ED to feed 

waters with TDS concentrations of 10,000 mg/L or less. 

Pre-treatment is necessary for ED to control scale buildup of calcium carbonate (CaCO3

) and magnesium 

hydroxide, as well as iron ions. Typically, these 

constituents are controlled either chemically by acid 

addition for pH adjustment and/or by cartridge filter. ED 

Treatment Company

Electrodialysis

Shale Gas Basin

Marcellus

Barnett

Haynesville

Fayetteville

Woodford

Use of this Technology has been considered but 

is currently not being utilized as a desalination

treatment technology by the Shale Gas industry.

KEY CONSIDERATIONS

 Standard ED is limited to treating TDS 

concentrations ranging from 4,000 mg/L to 

15,000 mg/L.

 ED is also capable of removing and/or reducing 

aluminum, barium, bromide, cadmium, calcium, 

chloride, copper, cyanide, potassium, and VOCs.

 ED is more expensive than RO but is more 

resistant to membrane fouling, which in turn can 

reduce costs
WATER TREATMENT TECHNOLOGY

FACT SHEET

Note: Information is from vendor, however specifications may have 

changed. Contact vendor for updates. Water Treatment Catalog and Decision Tool

is not effective at treating bacteria, colloidal material, 

boron or silica.

Costs

In general terms, electrodialysis is more expensive than 

RO but is more resistant to membrane fouling, which in 

turn can reduce costs typically associated with membrane 

replacement or cleaning. For Coal Bed Natural Gas

water, treatment costs have been estimated to be under 

15 cents per Bbl for a 0.34 MGD (8,000 bbl/day) 

treatment process.

ED treatment is more cost-effective and energy-efficient 

when treating low TDS water (e.g. TDS 4,000-5,000 

mg/L).

References

RosTek Associates, Inc, DSS Consulting, Inc., Aqua 

Resources International, Inc. Desalting Handbook for 

Planners Third Edition. Desalination and Water 

Purification Research and Development Program Report 

No. 72. July 2003.

ALL Consulting and Interstate Oil and Gas Compact 

Commission. 2006. A Guide to Practical Management of 

Produced Water from Onshore Oil and Gas Operations 

in the United States. Prepared for the U.S. Department 

of Energy National Petroleum Technology Office.

Younos, Tamim, K. E. Tulou. 2005. Overview of 

Desalination Techniques. Universities Council on Water 

Resources.

Department of the Army. 1986. Technical Manual, 

Water Desalination. TM 5-813-8.

Supplies: An Assessment Of Problems, Needs and 

Alternatives. Appendix II, Background Information on 

Treatment Methods and Distribution Systems. 

Hayes and Arthur, 2004. Overview of Emerging 

Produced Water Treatment Technologies. The 11th 

Annual International Petroleum Environmental 

Conference.

Colorado School of Mines. Produced Water Treatment 

and Beneficial Use Information Center. Treatment 

Options. Electrodialysis.

EET Corporation. 2010. HEED Specifications. March 22, 

2010.

EET Corporation. 2010. HEEPM Specifications. March 

22, 2010.