The ability to leach dyestuffs contained in municipal sludge using the Toxicity Characteristic Leaching Procedure (TCLP) was investigated. In addition to the dyestuffs, metals and other organic compounds which also leached were identified.

Only small amounts of color were detected in the TCLP extracts; the mean ADMI color values for undigested and aerobically digested sludges were 240 and 156 ADMI color units respectively. Concentrations of individual dyes that may have leached into the TCLP extracts were below detection limits. The reactive vinyl sulfone aniline moiety, which is released as a reduction product from the Remazol dyes used in the cellulosic textile dyeing industry, was found in the leachate from the sludge not treated by extended aerobic digestion. In the leachate from the sludge treated by extended aerobic digestion the reactive vinyl sulfone aniline reduction product was not found, suggesting that this compound was destroyed or rendered immobile by aerobic digestion. Metals leached from the sludge in trace amounts from 0.05 μg/L up to 1 mg/L. Several organic compounds detected in influent wastewater and in leachate from undigested sludge were not found in the leachate from digested sludge.