, Volume 17, Issue 3, pp 237–250 | Cite as

The ACCEL Model for Accelerating the Detoxification Kinetics of Hydrocarbons Requiring Initial Monooxygenation Reactions



The two-tank accelerator/aerator modification of activated sludge significantly increases the biodegradation of hydrocarbons requiring initial monooxygenation reactions, such as phenol and 2,4-dichlorophenol (DCP). The small accelerator tank has a controlled low dissolved oxygen (DO) concentration that can enrich the biomass in NADH + H+. It also has a very high specific growth rate (μ acc) that up-regulates the biomass’s content of the monooxygenase enzyme. Here, we develop and test the ACCEL model, which quantifies all key phenomena taking place when the accelerator/aerator system is used to enhance biodegradation of hydrocarbons requiring initial monooxygenations. Monooxygenation kinetics follow a multiplicative relationship in which the organic substrates (phenol or DCP) and DO have separate Monod terms, while the biomass’s content of NADH + H+ has a first-order term. The monooxygenase enzyme has different affinities (K values) for phenol and DCP. The biomass’s NADH + H+ content is based on a proportioning of NAD(H) according to the relative rates of NADH + H+ sources and sinks. Biomass synthesis occurs simultaneously through utilization of acetate, phenol, and DCP, but each has its own true yield. The ACCEL model accurately simulates all trends for one-tank and two-tank experiments in which acetate, phenol, and DCP are biodegraded together. In particular, DCP removal is affected most by DOacc and the retention-time ratio, Θacctotal. Adding an accelerator tank dramatically increases DCP removal, and the best DCP removal occurs for 0.2 < DOacc  < 0.5 mg/l and 0.08 < Θacctotal < 0.2. The rates of phenol and DCP utilization follow the multiplicative relationship with a maximum specific rate coefficient proportional to μacc. Finally, μ acc increases rapidly for Θacctotal < 0.25, acetate removal in the accelerator fuels the high μ acc, and the biomass’s NADH + H+ content increases very dramatically for DOacc < 0.25 mg/l.


activated sludge dichlorophenol monooxygenation nicotinamide adenine dinucleotide phenolics specific growth rate 


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  1. Bahder, TB 1995Mathematica for Scientists and EngineersAddison-Wesley Publishing Co., Inc.New YorkGoogle Scholar
  2. Dahlen, EP, 1999. Accelerating Detoxification by Manipulating Intracellular Electron Carriers, Ph.D. dissertation, Dept. of Civil Engineering, Northwestern University, Evanston, IL, USAGoogle Scholar
  3. Dahlen, E. P., Rittmann, B. E. 2000Analysis of oxygenation reactions in a multi-substrate system – a new approach for estimating substrate-specific true yieldsBiotechnol. Bioeng.70685692CrossRefGoogle Scholar
  4. Dahlen, E. P., Rittmann, B. E. 2002aTwo-tank suspended growth process for accelerating the detoxification kinetics of hydrocarbons requiring initial monooxygenation reactionBiodegradation13101116CrossRefGoogle Scholar
  5. Dahlen, EP, Rittmann, BE 2002bA detailed analysis of the mechanisms controlling the acceleration of 2.4-DCP monooxygenation in the two-tank suspended growth processBiodegradation13117130CrossRefGoogle Scholar
  6. Gottschalk, G. 1986Bacterial Metabolism2Springer-Verlag, Inc.New YorkGoogle Scholar
  7. Grady, CPL,Jr., Daigger, GT, Lim, HC 1999Biological Wastewater Treatment2Marcel Dekker, Inc.New YorkGoogle Scholar
  8. Kreyszig, E 1993Advanced Engineering Mathematics7John Wiley and Sons, Inc.New YorkGoogle Scholar
  9. Pavlostathis, SG, Giraldo-Gomez, E 1991Kinetics of anaerobic treatment: A Critical ReviewCrit. Rev. Env. Contr.21411490CrossRefGoogle Scholar
  10. Petzold, LR 1983Automatic selection of methods for solving stiff and nonstiff systems of ordinary differential equationsSIAM J. Sci. Stat. Comp.4136148CrossRefGoogle Scholar
  11. Rittmann, BE, McCarty, PL 2001Environmental Biotechnology: Principles and ApplicationsMcGraw-Hill Book Co.New YorkGoogle Scholar
  12. Rittmann, BE, Seagren, E, Wrenn, BA, Valocchi, AJ, Ray, C, Raskin, L 1994In Situ Bioremediation2Noyes Publishers, Inc.Park Ridge, NJ, USAGoogle Scholar
  13. Sáez, PB, Rittmann, BE 1993Biodegradation kinetics of a mixture containing a primary substrate (phenol) and an inhibitory co-metabolite (4-chlorophenol)Biodegradation4321CrossRefGoogle Scholar
  14. Wolfram, S 1994Mathematica, the Student BookAddison-Wesley Publishing Co., Inc.New YorkGoogle Scholar

Copyright information

© Springer 2006

Authors and Affiliations

  1. 1.ChemRisk, Inc.San FranciscoUSA
  2. 2.Center for Environmental Biotechnology Biodesign Institute at Arizona State UniversityTempeUSA

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