
                                  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.

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perspective to realize an increase in the reuse of grey water, as it would reduce or eliminate the volume of water withdrawn from surface waters.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)
   * 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. 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."
