Water

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In the following case study, Aquatech International Corp. discusses a water treatment system designed to minimize water usage and waste discharges, both liquid and solid, at a gas-fired combined cycle plant in California.

The electric power industry is a large water user and is dependent upon reliable water supplies. Adopting new water-conserving technologies for power production can help alleviate the impact of future water shortages. Several water use reduction technologies are available, each with different benefits and costs.

In much of the developing world, two essentials are often in short supply: potable water and reliable electricity. Some countries have invested heavily in desalination and combined cycle technologies to simultaneously solve both problems.

The U.S. Environmental Protection Agency (EPA) has a long history of making waves with the electric power industry because of its efforts to regulate the way thermal power plants construct and operate their cooling water intake structures (CWIS). These structures divert billions of gallons of water into power plants’ cooling systems and can injure or kill billions of aquatic organisms.

AES Gener recently completed construction of twin coal-fired, 260-MW units in the electricity-starved desert of northern Chile that may serve as models for future hybrid-fossil plant designs. For meeting an aggressive construction schedule, integrating a 20-MW battery energy storage system, embracing desalination, using the first-of-its-kind seawater cooling tower in South America, and employing innovative financing methods, the AES Gener Angamos plant has earned POWER’s 2012 Plant of the Year Award.

Combined Solar Technologies (CST) has designed, built, owns, and operates a water purification system located at the Musco Family Olive Co. facility in Tracy, Calif., that burns olive pits to purify highly saline wastewater through a distillation process while also producing electric power. For its pioneering approach, CST is the winner of POWER’s 2012 Marmaduke Award for excellence in plant problem-solving. The award is named for Marmaduke Surfaceblow, the fictional marine engineer and plant troubleshooter par excellence, whose exploits were chronicled in POWER beginning in 1948.

A West Coast combined cycle plant that uses reclaimed water found that cycling 300 times a year caused disruptions to the plant’s cooling water chemical treatment program. The solution was a performance-based monitoring and control system that uses available plant operating data plus algorithms to measure corrosion rates and fouling factors, which in turn allows the plant to trim chemical feed rates so they correlate with a specified corrosion rate, rather than a suggested chemical residual.

Efforts by power producers to meet clean air rules mean that wastewater effluent streams now face revised EPA regulations. A skirmish involving a New Hampshire power plant could set the tone for the next battle over regulations.

Exploiting the difference in salt concentrations between the freshwater runoff from river mouths at the point where they meet saltwater reservoirs such as seas and oceans to harness power isn’t a new thing.