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Note: Information is from vendor, however specifications may have changed. Contact vendor for updates. Water Treatment Catalog and Decision Tool 

### E L E C T R O D I A L Y S I S

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 pro cess 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 plac ed 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

membra nes 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 na rrow

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 E lectrodialysis, 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 co ntaminated 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 i t is capable of handling TDS levels up to 50,000 ppm and with water recover y 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 app licability 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 build

up of calcium carbonate (CaCO 3 ) and magnesium hydroxide, as well as iron ions. Typically, these

constituent s 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

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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 C o al 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

Desalinati on 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 Informa tion Center. Treatment Options. E lectrodialysis.

EET Corporation. 2010. HEED Specifications. March 22,

2010.

EET Corporation. 2010. HEEPM Specifications. March
22, 2010.