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Cooling water recovery is becoming common place in the power plant design strategydue to environmental restrictions on discharges, limitations on water supply, and theneed to expedite permitting of generation facilities.A conventional membrane process cannot function under high concentration ofhardness, silica and other organic limitation.For treatment of cooling tower blowdown, the engineers provided softening microfiltration, followed by high recovery reverse osmosis for pre-concentration of theblowdown. Finally, the blowdown will be treated in an evaporation pond to achievethe zero liquid discharge objectives.The blowdown recovery is a membrane process with a modified pretreatment schemeto accommodate high concentrations of dissolved solids including silica. It has beencommercially tested with silica levels in excess of 1600 ppm in the reject. Cooling towerblowdown recovery with the process is potentially more than 90% since the process islimited only by osmotic pressure. The process is also resistant to organic and biologicalfouling, which could potentially be present in the wastewater streams.The paper discusses the McClain Energy Facility, a new power plant in McClain, Oklahoma that utilizesthe blowdown recovery process to treat high silica cooling tower blowdown andprocess wastewater. The high purity product water is recycled back to the coolingtower thus reducing the fresh makeup water requirement and reducing wastewatervolume. The reject stream, which is about 10% of the original blowdown volume, isdischarged to an evaporation pond. The design resulted in substantial savings incapital and operating cost in achieving Zero Liquid Discharge in addition tomaximizing the reuse of raw water from a local wastewater treatment effluent. Includes table, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 8