Characterization of the microorganisms from an acclimated activated sludge degrading phenolic compounds

The microorganisms responsible for the degradation of a mixture of phenol, 4-chlorophenol (4CP), 2,4-dichlorophenol (24DCP) and 2,4,6-trichlorophenol (246TCP) were isolated and characterized in terms of its degradation rate. Activated sludge was acclimated for 70 days to 40 mg phenols/l. After this period the microorganisms responsible for the chlorinated phenol degradation were isolated and identified. Four types of Gram negative bacteria (Aeromonas sp., Pseudomonas sp. Flavimonas oryzihabitans, and Chryseomonas luteola) and Mycobacterium sp. were identified. The degradation kinetics of each phenol by Aeromonas sp., Pseudomonas sp. Flavimonas oryzihabitans, Chryseomonas luteola and activated sludge were determined. The degradation of phenolic compounds was sequential: phenol and 4CP were first degraded, following by 24DCP and then by 246TCP. The acclimated activated sludge was from one to two orders of magnitude faster than the pure strains, when uptake rates were calculated in terms of the viable biomass (CFU). The qx for acclimated activated sludge varied between 8.2 and 15.8 × 10−7 mg/CFU-d (407–784 mg/gVSS-d). Aeromonas sp. presented the highest qx 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) Pseudomonas sp. did. Specific substrate uptake rate was 1.8 mg chlorinated phenols/g VSS-d for non-acclimated activated sludge.