title: Two-tank suspended growth process for accelerating the detoxification kinetics of hydrocarbons requiring initial monooxygenation reactions.
abstract: An experimental evaluation demonstrated that suspended growth systems operated in a two-tank accelerator/aerator configuration significantly increased the overall removal rates for phenol and 2,4-dichlorophenol (2,4-DCP), aromatic hydrocarbons that require initial monooxygenations. The accelerator tank is a small volume that receives the influent and recycled biomass. It has a high ratio of electron donor (BOD) to electron acceptor (O2). Biomass in the accelerator should be enriched in reduced nicotinamide adenine dinucleotide (NADH + H+) and have a very high specific growth rate, conditions that should accelerate the kinetics of monooxygenation reactions. For the more slowly degraded 2,4-DCP, the average percentage removal increased from 74% to 93%, even though the volume of the two-tank system was smaller than that of the one-tank system in most experiments. The average volumetric and biomass-specific removal rates increased by 50% and 100%, respectively, in the two-tank system, compared to a one-tank system. The greatest enhancement in 2,4-DCP removal occurred when the accelerator tank comprised approximately 20% of the system volume. Biomass in the accelerator tank was significantly enriched in NADH + H+ when its dissolved oxygen (DO) concentration was below 0.25 mg/L, a situation having a high ratio of donor to acceptor. The accelerator biomass had its highest NADH + H+ content for the experiments that had the highest rate of 2,4-DCP removal. Biomass in the accelerator also had a much higher specific growth rate than in the aerator or the system overall, and the specific growth rate in the accelerator was inversely correlated to the accelerator volume.
authors.affiliation: Exponent Failure Analysis Associates, Menlo Park, CA 94025, USA. edahlen@exponent.com
authors.forename: Elizabeth P
authors.initials: EP
authors.lastname: Dahlen
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D001673:Biodegradation, Environmental; D002733:Chlorophenols / Q000378:metabolism*; D004867:Equipment Design; D006838:Hydrocarbons / Q000378:metabolism; D007220:Industrial Waste; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D018505:Waste Management / Q000295:instrumentation / Q000379:methods*; D014873:Water Pollutants / Q000378:metabolism
chemical_list: D002733:Chlorophenols; D006838:Hydrocarbons; D007220:Industrial Waste; D014873:Water Pollutants; D006899:Mixed Function Oxygenases; C004762:2,4-dichlorophenol