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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 way s 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 readil y 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perspective to realize an increase in the reuse of grey water, as it would reduce or eliminate the volume of water withdrawn from surface waters.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 coo ling 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.) wo uld serve the same purpose. But since the initial instructions related to grey water, that is the focus of this memo. EPA has also iss ue d the document Guidelines for Water Reuse ( EPA 625/R- 04/108 ) , w

hich may be insightful.2

 Rawhide Energy

Station , Fo rt Collins, C O (once - through)  Curtis Stanton Energy Facility , Orlando, F L (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 anal ys is of once - through cooling at power plants :
 Grey water is very

rarel y available in sufficient quantity to supply once - through cooling water for an industrial facility . It is much more fea sible as a consideration for makeup water for a closed - cycle sy stem 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, i n 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 suppl y of grey water is insuff icient 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 . 2 The anal ys is noted that there are large volumes of grey water availabl e 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 sy stem, 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 In formation 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 sy stem. ” 3

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 Wate r 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.