Cause and Remediation of Hydrogen Sulfide Emissions from a Sodium-Based Flue Gas Desulfurization Sludge Disposal Pond
A flue gas desulfurization (FGD) sludge disposal pond with a history of H2S emissions to the atmosphere was studied to determine the cause of emissions and remediation strategies. The pond receives sludge and associated waters from a single-pass Na2CO3 flue gas scrubber unit. The pond water is a sodic alkaline brine with large SO3 and S2O3 concentrations (>5000 mg L-1), and hence, an elevated chemical O2 demand. The pond water H2S concentrations are small as a result of periodic H2O2 additions. The sediments, however, have as much as 3500 mg L-1 H2S in the pore water. The production of H2S appeared to originate from the sediments and diffuses through the anoxic water column with little oxidation. Large concentrations of the reduced sulfur species SO3 and S2O3 were present as a result of the flue gas desulfurization process and incomplete oxidation of H2S. The pond was reconstructed to circulate the water through an air injection system that was designed to oxidize the SO3 and S2O3 to SO4, and thereby reduce the chemical O2 demand. After the installation of the air injection system, emissions of H2S ceased and the concentrations of SO3 and S2O3 were reduced by at least a factor of 10 within 3 to 4 wk. The production of H2S in the sediments, however, did not appear to be affected, nor did it appear that it will be reduced in the future by the air injection system.
Revised: November 6, 2020 |
Published: March 31, 1995