The fate of chlorinated phenols in upflow anaerobic sludge blanket reactors.

Abstract

Five trichlorophenols (2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6-trichlorophenol) and one dichlorophenol (3,5-dichlorophenol) were continuously treated in upflow anaerobic sludge blanket reactors for eight months. Their anaerobic biodegradation pathways and toxicity loading limits were determined. It was found that ortho positioned chlorine was readily removed from tri- and dichlorophenols. With acclimation, meta position chlorine was also removed from 3,4-, 3,5-dichlorophenols. Although there was no evidence of 3- and 4-monochlorophenol being degraded, the mass balance of the chlorophenols indicated that more than 50% of the 3-monochlorophenol formed from its parent compounds had disappeared, and the disappearance of 4-monochlorophenol was 20%. Acclimation and adequate alternate carbon sources reduced inhibition by chlorophenols. Inhibition was caused by: 2,4,5-trichlorophenol at a specific loading rate of 0.3 mg/g volatile suspended solids (hydraulic retention time of 3 days) and 0.9 mg/g volatile suspended solids (hydraulic retention time of 1 day); 2,3,4-trichlorophenol at a specific loading rate of 2.5 mg/g volatile suspended solids (hydraulic retention time of 1 day); 2,3,5-trichlorophenol at a specific loading rate of 1.25 mg/g volatile suspended solids (hydraulic retention time of 1 day); 3,5-dichlorophenol at a specific loading rate of 3.0 mg/g volatile suspend solids (hydraulic retention time of 1 day). The sorption isotherms of all the mono-, di- tri-chlorophenols as well as pentachlorophenol were determined. Biosorption of chlorophenols by anaerobic granular biomass fitted the Freundlich model. Biosorption of chlorophenols increased with increasing halogenation of the chlorophenols. The conditions used in batch sorption tests were similar to those in upflow anaerobic sludge blanket systems. The biosorption constants determined were successfully used to estimate the amount of chlorophenols sorbed by biomass in upflow anaerobic sludge blanket systems. Biosorption accounted for as much as 6% of the total chlorophenol removal. (Abstract shortened by UMI.)