Using Filter Presses in Flue Gas Desulfurization Wastewater Treatment
Coal-Fired Power Plants are Producing Over Half of Our Nation’s Electricity
Coal is the primary resource in the U.S. for producing electricity, and is currently generating over half of the electrical power used in our nation today. Coal offers over 274 billion tons of untapped supplies, which according to Industrial Water World, is enough to energize America for 250 years. New coal-fired power plants are being built and existing U.S. plants are being retrofitted for environmental compliance.
Coal combustion results in energy release, solid waste produced as bottom ash and fly ash, and flue gas emissions to the atmosphere. These gas emissions are made up of sulfur oxides (SOx), nitrogen oxides (NOx), carbon monoxide and other pollutants. About two thirds of SOx and a quarter of all NOx in our atmosphere come from the generation of electric power from coal and other fuels. SOx causes acid rain, and NOx creates atmospheric ozone.
SOx compliance requires the use of flue gas desulfurization (FGD). One of the most effective methods used in the U.S. to desulfurize flue gas is wet scrubbing, which can achieve SOx removal efficiency of greater than 90%. (Source: waterworld.com).
Flue Gas Desulfurization Wastewater Treatment
Following the wet scrubbing FGD process, the resulting wastewater must be treated before being released to surface water. FGD wastewater is highly complex, and its composition can vary significantly between plants. Flue gas desulfurization wastewater is often made up of multiple key contaminants, including high concentrations of TDS and TSS, nitrites and nitrates and trace amounts of heavy metals.
Because of its unique composition, FGD wastewater requires several steps to meet National Pollutant Discharge Elimination System (NPDES) requirements prior to discharge. This treatment typically includes the following steps: Calcium sulfate (gypsum) desaturization, primary clarification, equalization, trace metals precipitation, secondary clarification, filtration and solids dewatering. (Source: powermag.com).
While the design of a FGD wastewater treatment system can vary by power plant due to differences in contaminants, a filter press is commonly used for the separation of solids from liquids in the waste stream. After dewatering in a filter press, the solids are discharged as a filter cake for disposal in a landfill. The treated wastewater is either discharged to surface water or polished with a gravity filter to further reduce suspended solids prior to discharge.
Contact M.W. Watermark to learn more about how filter presses can be used in the process of treating flue gas desulfurization wastewater.
About M.W. Watermark
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