Bioregeneration of powdered activated carbon (PAC) loaded with aromatic compounds

Bioregeneration of powdered activated carbon (PAC) loaded with aromatic compounds was quantitatively determined using carbon dioxide production as a measure of substrate consumption. Two types of powdered activated carbon (one chemically activated, wood-based carbon, CA1, and one thermally activated, peat-based carbon, SA4) and two aromatic compounds (o-cresol and 3-chlorobenzoic acid) in single solute batch systems were used. Interaction of EDTA, present as chelating agent in all experiments with o-cresol as substrate, and SA4 resulted in abiotic CO2 production (in absence of microorganisms). The extent of bioregeneration varied considerably, from 15 to 85% of total PAC loading, depending on type of PAC used and compound involved and, in one case, on the time of contact between PAC and the compound. The results revealed that the data corresponded with a mechanism of bioregeneration where desorption precedes biodegradation. Microorganisms reduced the dissolved compound concentration, forcing desorption and subsequent biodegradation, but were unable to influence the desorbability of the PAC-sorbed compounds. The practical applicability of the results is discussed.