title: Effect of long-term exposure, biogenic substrate presence, and electron acceptor conditions on the biodegradation of multiple substituted benzoates and phenolates.
abstract: Biodegradation rates of benzoate and related aromatic compounds, 3-nitrobenzoate, 4-chlorobenzoate, 4-chlorophenol, and 2,4-dichlorophenol by unexposed (unacclimated) and long-term exposed (acclimated) biomass were quantified using a modified fed-batch technique. The acclimated biomass was taken after approximately 1-year of operation from three lab-scale sequencing batch reactors (SBR). These reactors were operated under various cycling electron acceptor conditions with a continuous feed of a synthetic wastewater containing biogenic and nonbiogenic chemicals including benzoate, 3-nitrobenzoate, and 4-chlorophenol, but not 4-chlorobenzoate or 2,4-dichlorophenol. The unexposed biomass was taken from a full-scale wastewater treatment plant, which constituted one of the original sources of inoculum for the lab-scale SBRs. The acclimated biomass manifested high removal rates of benzoate and related aromatic compounds with additional removal of structurally similar chemicals (4-chlorobenzoate and 2,4-dichlorophenol). The unacclimated biomass showed no removal of 3-nitrobenzoate, 4-chlorobenzoate or 2,4-dichlorophenol. Addition of biogenic substrates reduced the degradation of most aromatic compounds tested, but it enhanced 2,4-dichlorophenol removal. Biodegradation rates of each aromatic compound with the biomass from the anoxic/aerobic SBR were further determined under anaerobic (absence of aeration and NO3-), anoxic (no aeration, but with surplus NO3-), standard oxygen (DO > 0.2 mg/L), and elevated oxygen (DO > 25 mg/L) conditions. The removal rate of both benzoate and 3-nitrobenzoate decreased under anaerobic condition but not under the anoxic condition; 4-chlorophenol biodegradation, on the other hand, was reduced significantly under both anoxic and anaerobic conditions. The removal rates of aromatic compounds, particularly those of 3-nitrobenzoate and 2,4-dichlorophenol, increased significantly under elevated dissolved oxygen conditions. Our results demonstrated that when the biochemical conditions shifted from oxygen-respiration to nitrate respiration, to anaerobiosis, the biodegradation rates of test aromatic compounds decreased or ceased.
authors.affiliation: Environmental Engineering Program, Department of Civil & Environmental Engineering, University of Connecticut, Storrs, CT 06269-2037, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Hu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Ferraina
authors.forename: Jon F
authors.initials: JF
authors.lastname: Ericson
authors.forename: Barth F
authors.initials: BF
authors.lastname: Smets
mesh_terms: D000327:Adsorption; D000332:Aerobiosis; D000693:Anaerobiosis; D000818:Animals; D001419:Bacteria / Q000378:metabolism; D001565:Benzoates / Q000378:metabolism; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors; D002723:Chlorobenzoates / Q000378:metabolism; D002733:Chlorophenols / Q000378:metabolism; D008892:Milk; D009566:Nitrates / Q000378:metabolism; D009579:Nitrobenzoates / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D001565:Benzoates; D002723:Chlorobenzoates; D002733:Chlorophenols; D009566:Nitrates; D009579:Nitrobenzoates; D014874:Water Pollutants, Chemical; C029107:4-chlorophenol; C040770:3-nitrobenzoic acid; C040768:4-chlorobenzoic acid; C004762:2,4-dichlorophenol; D010100:Oxygen