Page 2 of 3
The first or raw cost of the water is, however, not the final cost if treated water is used. Table 2 identifies the add-on costs necessary to treat a variety of waters using both the “conventional” (chemical) and MF/RO (microfiltration/reverse osmosis) processes. Using 1 as a basis factor for the U.S., the reader will note, increasing costs associated with conventional treatment, a similar cost for MF/RO and a significantly higher cost associated with MF/RO TSE treatment in the UAE of the Middle East.
A prime example
Every day U.S. industries consume some 410 billion gallons of water while generating about 20 billion gallons of wastewater. Thermoelectric plants in the U.S. consume nearly 50 percent of this total, or some 186 billion gallons of water. Given the voluminous flows and declining resources, impaired water, as an alternate cooling medium, has emerged as a trendy option.
The Arizona Public Service Palo Verde Generating Station (APS-PV) remains the largest example for the continued use of impaired water or TSE for power plant cooling. Palo Verde is a three-unit, PWR facility generating a total of 3,875 MW and provides electric power to 4 million people in the Southwest U.S. The station has been in operation since 1986 and uses TSE exclusively for cooling as make-up to the mechanical draft cooling towers.
An expected 20-year operating license renewal for APS-PV, coupled with a recent 40-year agreement with 5 local Phoenix-area communities for the long term supply of TSE provided both a reliable source of power to the desert southwest while maintaining predictable revenue to the local economy.
Research has uncovered an increasing number of new or existing generating facilities that have employed the use of impaired water in some form of cooling – primarily as tower makeup and, rarely, in direct, once-through cooling (Table 3). A new mix of not only TSE and other similar variants but brackish groundwater and oil-field produced water suggests a continuing expansion in U.S. applications. Additionally, the HVAC refrigerant and hydrocarbon process industries in the Middle East have integrated this cooling medium.
Reclaimed water is currently in use at the SCE Mountainview Power Plant CCGT (MVPP). This plant is located in Redlands, Calif., and utilizes treated municipal effluent and perchlorate-contaminated groundwater for power plant cooling. What is unique here is that the MVPP employs a wastewater treatment system that recovers up to 75-80 percent of the water that would normally be disposed of in the form of dewatered solids or to municipal drain.
Fracking – a 4-letter word?
Fracking, or hydraulic fracturing, is the propagation of fractures in a rock layer caused by the presence of a pressurized fluid. Hydraulic fractures might form naturally, as in the case of veins or dikes, or might be man-made in order to release petroleum, natural gas, coal seam gas or other substances for extraction. Water is by far the largest component of fracking fluids, often initially consuming as much as 65,000 to 600,000 gallons. Throughout the life and restimulation of an average well, this number could go as high as 4 million gallons per well. By any definition, this is not typical water. It is estimated by one fracking fluid manufacturer that 279 different products were contained in the proprietary “witches brew” of injection fluid. And just this process makes recovery, treatment and reuse difficult at best. The fact that many companies treat the injection fluid as a trade secret further complicates the issue.