Performance evaluation of a continuous packed bed bioreactor: Bio-kinetics and external mass transfer study

Area of Science:

• Environmental microbiology
• Bioreactor engineering
• Bioremediation

Background:

• Naphthalene is a persistent organic pollutant requiring effective remediation strategies.
• Microbial degradation offers a sustainable approach to remove naphthalene from contaminated environments.
• Immobilization of microorganisms enhances bioreactor performance and stability.

Purpose of the Study:

• To investigate the biodegradation of naphthalene using Exiguobacterium sp. RKS3 immobilized on LDPE in a continuous packed bed bioreactor (PBBR).
• To evaluate the impact of varying inlet flow rates (IFRs) on naphthalene removal efficiency (RE).
• To develop a correlation for predicting external mass transfer (EMT) and determine biodegradation kinetics.

Main Methods:

• Continuous operation of a packed bed bioreactor (PBBR) with LDPE-immobilized Exiguobacterium sp. RKS3.
• Systematic variation of inlet flow rates (20-100 mL/h) over 64 days.
• Analysis of external mass transfer using Colburn factor (J_D) and Reynolds number (N_Re), and application of the Andrew-Haldane model for kinetic analysis.

Main Results:

• Maximum naphthalene removal efficiency (RE) was achieved at lower inlet flow rates (IFRs), decreasing as IFRs increased.
• A new correlation was established to predict the external mass transfer (EMT) aspect of naphthalene biodegradation.
• Andrew-Haldane model yielded kinetic constants: ν_max = 0.386 per day, J_s = 13.6 mg/L, and J_i = 20.54 mg/L.

Conclusions:

• Continuous PBBR with LDPE-immobilized Exiguobacterium sp. RKS3 is effective for naphthalene biodegradation.
• Inlet flow rate significantly influences naphthalene removal efficiency, with lower rates being more favorable.
• The developed correlation and kinetic parameters provide valuable insights for optimizing bioreactor design and operation for naphthalene removal.