Modeling hexavalent chromium removal in a Bacillus sp. fixed-film bioreactor

Evans M. Nkhalambayausi-Chirwa, Yi Tin Wang

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


A one-dimensional diffusion-reaction model was developed to simulate Cr(VI) reduction in a Bacillus sp. pure culture biofilm reactor with glucose as a sole supplied carbon and energy source. Substrate utilization and Cr(VI) reduction in the biofilm was best represented by a system of (second-order) partial differential equations (PDEs). The PDE system was solved by the (fourth-order) Runge-Kutta method adjusted for mass transport resistance using the (second-order) Crank-Nicholson and Backward Euler finite difference methods. A heuristic procedure (genetic search algorithm) was used to find global optimum values of Cr(VI) reduction and substrate utilization rate kinetic parameters. The fixed-film bioreactor system yielded higher values of the maximum specific Cr(VI) reduction rate coefficient and Cr(VI) reduction capacity (kmc = 0.062 1/h, and Rc = 0.13 mg/mg, respectively) than previously determined in batch reactors (kmc = 0.022 1/h and Rc = 0.012 mg/mg). The model predicted effluent Cr(VI) concentration well with 98.9% confidence (σy2 = 2.37 mg2/L2, N = 119) and effluent glucose with 96.4% confidence (σ y(w)2 = 5402 mg2/L2, N = 121, w = 100) over a wide range of Cr(VI) loadings (10-498 mg Cr(VI)/L/d).

Original languageEnglish
Pages (from-to)874-883
Number of pages10
JournalBiotechnology and Bioengineering
Issue number7
StatePublished - Sep 30 2004


  • Bacillus sp.
  • Biofilm kinetics
  • Chromium(VI)
  • Genetic search algorithm
  • Mass transport

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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