Calcium-based flue gas desulfurization sludge disposal ponds. Final report

Technical Report · Fri Apr 01 04:00:00 EST 1994

OSTI ID:10160491

Ainsworth, C C; Rai, D; Resch, C T ^[1]

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1. Battelle Pacific Northwest Lab., Richland, WA (United States)

Four flue gas desulfurization (FGD) sludge disposal ponds at coal-fired power plants employing calcium (Ca)-based FGD scrubbing systems were selected for sampling and characterization. Two of the power plants use forced-air oxidation (FAO). Samples of inflow, pond water, and FGD sludge solids were obtained at each site and analyzed using on-site and laboratory techniques to characterize pond chemistry and microbiology, and to identify common or distinguishing biogeochemical reactions that affect the long-term disposal of FGD sludge. Dense populations of heterotrophic, anaerobic bacteria capable of reducing sulfate (SO{sub 4}{sup 2{minus}}) to sulfide (S{sup 2{minus}}) were observed in all sampled Ca-based FGD sludges. The chemical composition of the pond and pore waters included adequate concentrations of dissolved organic carbon for bacterial metabolism. Regardless of predisposal treatment the sludge sediments the sludge sediments developed a greatly reduced anaerobic environment, probably due to microbial activity and low gas permeability; the low redox potential of the sludge was conducive to dissimilatory microbial reduction of SO{sub 4}{sup 2{minus}} to S{sup 2{minus}}. The results suggest that regardless of the type of coal burned in electric power generation, the kind of Ca-based scrubbing material used, or use of forced air oxidation prior to disposal, certain biogeochemical reactions are generic to controlling the leachate chemistry of FGD sludge ponds. Aside from the generic chemical precipitation reactions noted above, the microbial production of sulfide appears to be common to all the ponds that were investigated. As a consequence of this sulfide production, aqueous concentrations of trace metals such as Pb, Zn, Cu, Hg, Cd, etc. will be controlled by the precipitation of the metal-sulfide minerals.

• Research Organization: Electric Power Research Inst., Palo Alto, CA (United States); Battelle Pacific Northwest Lab., Richland, WA (United States)
• Sponsoring Organization: Electric Power Research Inst., Palo Alto, CA (United States)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 10160491
• Report Number(s): EPRI-TR--103914; ON: UN94013848
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010800
20 FOSSIL-FUELED POWER PLANTS
200202
ANAEROBIC CONDITIONS
BACTERIA
CADMIUM
CHEMICAL COMPOSITION
COPPER
DESULFURIZATION
ELEMENTS
FLUE GAS
FOSSIL-FUEL POWER PLANTS
LEACHING
LEAD
MERCURY
NOXIOUS GAS AND PARTICULATE EMISSIONS
PONDS
SCRUBBERS
SLUDGES
SULFATE-REDUCING BACTERIA
SULFIDES
TRACE AMOUNTS
WASTE DISPOSAL
WASTE MANAGEMENT
ZINC