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The new limits on heavy metal discharges mean that considerable time for floc buildup is necessary in the mixing time. The pump that discharges this slurry to the clarifier should be a progressive cavity pump which does not shear the floc. Centrifugal pumps break up the floc and reduce the ability of the clarifier to separate out selenium, mercury, and other metal species. Many power plants are planning to install these systems due to new awareness that excess amounts of toxic metals are entering the waterways due to FGD scrubbing. |
