One of the largest power producers in the U.S. has selected Siemens Water Technologies to provide a system to treat wastewater from a Flue Gas Desulphurisation (FGD) scrubber being constructed at a power plant in the eastern U.S.
Siemens Water Technologies explains that the installation of the wet scrubber will significantly reduce emissions of mercury and sulphur dioxide. The wastewater treatment system will remove suspended solids and heavy metals from the scrubber waste stream so the water can be safely discharged. Siemens’ scope of supply on the new physical/chemical wastewater treatment system for this project includes system design, equipment supply, project management, system start-up, staff training, and system commissioning. When completed in 2012, the system will be Siemens’ 14th FGD scrubber wastewater treatment system installed at a U.S. power plant.
According to the company, scrubbers are used in numerous U.S. power plants to meet emissions standards set by the U.S. Environmental Protection Agency (EPA) and/or state agencies. Flue gas systems frequently use limestone-forced-oxidation (LSFO) scrubbers to convert SO2 in the flue gas to gypsum, which can be recycled and sold for wallboard manufacturing, cement additive, or agricultural applications – turning a waste stream into a usable resource.
The system from Siemens will include an equalization tank, reaction tank, chemical feed systems, clarifier, gravity sand filters, sludge holding tanks, and recessed chamber filter presses. The equalization tank receives the waste stream and attenuates the flow to eliminate spikes in flow rates and concentration. The reaction tank’s purpose is to de-saturate the wastewater and prepare the wastewater for clarification. A chemical to enhance flocculation is added to the reaction tank. Next, the wastewater flows to a clarifier in which polymer is added to cause the suspended solids to coagulate and settle. Solids from the clarifier are directed to sludge holding tanks prior to dewatering in the filter presses. The treated water from the clarifiers flows to gravity sand filters for final treatment, and is then ready for discharge.