Regeneration of the Fe(II)-EDTA scrubbing liquors for simultaneous removal of SO2 and NO(x) in flue gas involves removing the nitrogen-sulfur (N-S) compounds accumulated in the liquor. In this paper, we investigate a simple regeneration process which selectively precipitates the N-S compounds as potassium salts and then hydrolyzes them to yield ammonium/potassium sulfate as a marketable byproduct. We believe this is the first report on precipitation and hydrolysis characteristics of N-S compounds in actual waste scrubbing liquor. Precipitation of the N-S compounds was achieved by adding K2SO4 to the scrubbing liquor. The effects of the amount of added K2SO4 on the amount of removed N-S compounds, precipitated crystals, and potassium left over in the scrubbing liquor were studied. Hydrolysis of the precipitated N-S compounds to ammonium sulfate was performed in a sulfuric acid environment. The effects of acidity, concentration of N-S compounds, and temperature of the hydrolysis are discussed. Analysis of the observed hydrolysis pattern showed that the reaction proceeded following first-order kinetics in terms of N-S compound concentration.