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Simulation of Phenol Biodegradation by Pseudomonas Putida in a Continuous Stirred Biofilm Reactor

Alinejad, Mahsa | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56793 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Yaghmaei, Soheila; Askaripour, Hossein
  7. Abstract:
  8. The use of microorganisms to remove or produce a substace is a fundamental part of biotechnology. An example is the bioreactors for phenol removal in wastewater. Biological processes are commonly done in batch reactors in which suspended cells grow in the liquid phase. The batch process needs alternate reactor washes and alternate cell cultivation, which leades to a longer time constant for for each batch. If these reactors operate in continuous conditions, the cells will leave the reactor in liquid flow, and high cell concentrations will be impossible. The biofilm layer makes a batch phase, so the liquid phase flows in and out continuously, but the cells in the biofilm layer stay in the reactor, and cell concentration will always be high. The governing system of equations is nonlinear with multiple steady-state solutions, which is hard to solve using standard numerical methods. In this thesis, a mathematical model for a stirred tank bioreactor with a biofilm layer on carrier particles is developed. The reactor has three phases: the continuous liquid and gas phases, which bring carbon and oxygen into the reactor, and the batch biofilm phase, in which the biological reaction occurs. This bioreactor considers phenol biodegradation using Pseudomonas putida bacteria. The mathematical model considers inter-phase mass transfer, diffusion through the biofilm layer, biomass detachment from the biofilm layer, biological reaction in biofilm and liquid phases, and biofilm thickness variation. The model is proposed for both steady and unsteady conditions. The continuation algorithm was used to find steady states for different parameters. The influence of liquid-biofilm mass transfer coefficient, liquid-gas mass tranfer coefficient, biofilm detachment coefficient, and carrier particles fraction was studied. Validation with experimental data shows the biofilm thickness of 28.5 µm for carrier particles of 307 µm diameter has good agreement with data from a laboratory scale fluidized bed bioreactor. The simulation results show that phenol concentration decreased from 500 mg/L to lower than 3 mg/L in a continuous biofilm bioreactor with 7 hours of residence time. It is also shown that the biofilm layer experience phenol inhibition in concentrations higher than that of liquid phase. A slower dynamic response to inlet phenol concentrations disturbance than residence time disturbance was observed
  9. Keywords:
  10. Stirred Tank Reactor ; Biodegradation ; Biofilm ; Stability ; Phenol Removal ; Pseudomonas Putida Bacteria ; Carrier Particles ; Phenol Biodegradation

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