Siemens to supply FGD scrubber system at three Mirant plants

The Shaw Group has selected Siemens Water Technologies to provide a system to treat wastewater from Flue Gas Desulfurization scrubbers being constructed at Mirant Mid-Atlantic's Dickerson and Morgantown Power Plants and Mirant Chalk Point's Chalk Point Power Plant. The system will remove suspended solids, heavy metals and organics from the scrubber waste stream so that the water can be safely discharged. Located in Maryland, the wastewater projects are scheduled to begin operation in 2010...

WARRENDALE, PA, March 26, 2008 -- The Shaw Group Inc., has selected Siemens Water Technologies to provide a system to treat wastewater from Flue Gas Desulfurization (FGD) scrubbers being constructed at Mirant Mid-Atlantic, LLC's Dickerson and Morgantown Power Plants and Mirant Chalk Point, LLC's Chalk Point Power Plant. The system will remove suspended solids, heavy metals and organics from the scrubber waste stream so that the water can be safely discharged. Located in Maryland, U.S., the wastewater projects are scheduled to begin operation in 2010.

Scrubbers are used in U.S. power plants to meet emissions standards set by the U.S. Environmental Protection Agency (EPA). New regulatory programs call for further reduction of sulfur dioxide (SO2) emissions from coal-burning power plants. Flue gas systems frequently use limestone-forced-oxidation (LSFO) scrubbers to convert SO2 in the flue gas to gypsum, which can be sold for wallboard manufacturing, cement additive, or agricultural applications, thus turning a waste stream into a usable resource.

The proper design of wastewater treatment systems and the selection of materials of construction are critical. Both of these key items can have a major impact on the treatment plant's operation and reliability. Siemens Water Technologies will provide the new physical/chemical and biological wastewater treatment system on an equipment design-supply basis and provide start-up, training and commissioning services. The Shaw Group Inc. will be responsible for installing the equipment. Each wastewater system will include storage tanks, reaction tanks, chemical feed systems, a clarifier, biological reactors, gravity sand filters and filter presses. The system flow rates are 200 gallons per minute (gpm) (45 m³/h) for the Morgantown plant and 110 gpm (25 m³/h) each for the Dickerson and Chalk Point plants.

An equalization tank receives the waste stream and equalizes the flow to eliminate spikes in flow rates and concentration. Next, two reaction tanks in series continue the treatment process to de-saturate the wastewater, reduce heavy metals, and prepare the wastewater for clarification. The treated wastewater then enters the clarifier, where suspended solids are coagulated and settled. Solids from the clarifier are dewatered in the filter presses. The treated water is sent from the clarifier to sequencing batch biological reactors for nitrogen reduction. The remaining treated water is sent to gravity sand filters for final treatment before discharge.

The largest power plant in Maryland, Chalk Point Generating Station is located on the Patuxent River. The plant has 683 MW of coal-fired capacity and serves over 2 million homes in Prince George's County. The Morgantown Generating Station, located on the Potomac River in Charles County, has 1,164 MW of coal-fired capacity and serves almost 1.5 million homes in the area. Dickerson Generating Station is also located on the Potomac, in Montgomery County. Dickerson has 546 MW of coal-fired capacity and serves over 800,000 homes in the area.

To date, Siemens has supplied 13 FGD wastewater treatment systems at U.S. power plants.

The Shaw Group Inc., with headquarters in Baton Rouge, Louisiana, provides engineering, design, construction and maintenance services to government and private-sector clients in a wide array of industries, including the energy, environmental, infrastructure and emergency response markets.

The Siemens Industry Sector (Erlangen, Germany) is a leading supplier of production, transportation and building systems.

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