Biodegradation of phenolic compounds by an acclimated activated sludge and isolated bacteria

Abstract

The degradation of a mixture of phenol, 4-chlorophenol (4CP), 2,4-dichlorophenol (24DCP) and 2,4,6-trichlorophenol (246TCP) by acclimated activated sludge and by isolated bacteria was studied. Activated sludge was acclimated for 70 days to 40 mg phenols/l then the microorganisms responsible for the CP degradation were isolated and identified. Four types of Gram-negative bacteria (Aeromonas sp., Pseudomonas sp. Flavomonas oryzihabitans, and Chryseomonas luteola) were identified. Also, two acid-fast bacilli with distinct glycolipid patterns were isolated. From their chemical composition and their growth characteristics, both isolates appeared to be mycobacteria closely related to Mycobacterium peregrinum. The degradation kinetics of each phenol by Aeromonas sp., Pseudomonas sp. Flavomonas oryzihabitans, Chryseomonas luteola and activated sludge were determined. The acclimated activated sludge degradation rates were from one to two orders of magnitude higher than those of pure strains when uptake rates were calculated in terms of the viable biomass (CFU). The specific substrate uptake rate for acclimated activated sludge varied between 8.2 and 15.8 × 10−7 mg/CFU·d (407-784 mg/gVSS·d). Aeromonas sp. had the highest specific substrate uptake rate of the pure strains, based on a VSS basis (33-57 mg/gVSS·d) but, in terms of viable biomass (5.0-15.6 × 10−8 mg/CFU·d), the Pseudomonas sp. rate was the highest. Specific substrate uptake rates were 1.8 mg chlorinated phenols/g VSS·d for unacclimated activated sludge.