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MEMORANDUM

Tetra Tech, Inc.

10306 Eaton Place, Suite 340

Fairfax, VA 22030

phone 703-385-6000

fax 703-385-6007

TO: Lisa Biddle, EPA

FROM: Kelly Meadows

DATE: November 30, 2012

SUBJECT: Use of Grey Water for Cooling Purposes

Tetra Tech was tasked with identifying ways that the final Existing Facility rule could encourage 

greater use (or consideration) of grey water (treated effluent from POTWs, also referred to as 

reclaimed water) for cooling purposes.1

Background

Grey water is a readily available source of water and, much like encouraging the reuse of process 

and contact cooling water at manufacturing facilities, it would be beneficial from an 

impingement and entrainment (I&E) perspective to realize an increase in the reuse of grey water, 

as it would reduce or eliminate the volume of water withdrawn from surface waters. As a result, 

a facility might achieve partial or full elimination of I&E.

EPA is aware of several examples where a facility uses grey water for cooling purposes, 

including:

 Linden Generating Station (see site visit report at DCN 10-6557)

 Encina Power Station (dry cooling after repowering, but some cooling water needs will 

be satisfied with grey water)

Other examples were identified in a brief internet search:

 Bethlehem Steel, Baltimore, MD (once-through)

 

1 Note that this discussion does not have to be limited to grey water; any alternative source of water (treated 

industrial effluent, stormwater, groundwater, etc.) would serve the same purpose. But since the initial instructions 

related to grey water, that is the focus of this memo. EPA has also issued the document Guidelines for Water Reuse

(EPA 625/R-04/108), which may be insightful. 
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 Rawhide Energy Station, Fort Collins, CO (once-through)

 Curtis Stanton Energy Facility, Orlando, FL (cooling tower make-up)

However, there are a number of challenges associated with the use of grey water, as noted in the 

documentation for California’s analysis of once-through cooling at power plants:

 Grey water is very rarely available in sufficient quantity to supply once-through cooling 

water for an industrial facility. It is much more feasible as a consideration for makeup 

water for a closed-cycle system or a small industrial facility.

 Grey water may not be locally available to a given facility; piping the grey water over 

long distances introduces a substantial extra cost.

 Grey water is, in some cases, also sought after for other purposes, such as supplementing 

the natural stream flow of a waterbody, irrigation, or restoring groundwater supplies.

 Backup water sources must be identified for situations where the supply of grey water is 

insufficient to meet cooling water needs.

California examined the availability of grey water sources within a 15-mile radius of each of the 

coastal power plants subject to the state policy.

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The analysis noted that there are large volumes 

of grey water available near some power plants, but did not make any specific requirements for 

its use. The state staff recommended that the state policy “[r]equire that power plant owners 

consider the feasibility of using recycled wastewater for power plant cooling, either to 

supplement OTC or as makeup water in a closed-cycle system, when developing their 

implementation plans.”

When examining each facility for potential compliance with the state cooling water policy, 

California noted that

“In order to be a practical alternative, reclaimed water must, at a minimum, meet 

the following criteria: 

 Treatment to tertiary standards or ability to provide treatment onsite

 Minimum available flow equal to the design makeup demand

 Relative proximity to the facility

 Consistency of delivery

Information regarding potential sources of reclaimed water is included in each 

facility’s discussion chapter, although all comprehensive cost estimates are 

developed based on the assumption that the existing marine source water will 

continue to provide makeup water to the retrofitted system.”

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2

See Table 14 in Water Quality Control Policy on the Use of Coastal and Estuarine Waters for Power Plant 

Cooling: Final Substitute Environmental Document, State Water Resources Control Board and California 

Environmental Protection Agency, May 4, 2010.

3

See Chapter 5 in California’s Coastal Power Plants: Alternative Cooling System Analysis, Final Report, California 

Ocean Protection Council, February 2008.