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Toluene removal in an automated cyclical bioreactor
W A Brown1, D G Cooper, S N Liss
1Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec H3A 2B2, Canada.
Biotechnology Progress
|June 3, 2000
Summary
A new control scheme for bioreactors effectively removes toluene using oxidation-reduction potential (ORP) signals. Second derivative ORP control achieved 95% toluene removal efficiency, significantly improving upon first derivative methods.
Area of Science:
- Biotechnology and Bioengineering
- Environmental Engineering
- Chemical Engineering
Background:
- Cyclical bioreactors are crucial for industrial bioprocesses, but efficient contaminant removal, like toluene, remains a challenge.
- Automation of bioreactor operations can enhance efficiency and stability.
- Oxidation-reduction potential (ORP) is a key indicator of microbial activity and redox balance in bioreactors.
Purpose of the Study:
- To develop and evaluate an automated control scheme for efficient toluene removal in a cyclical bioreactor.
- To identify the most effective control variable for automating toluene biodegradation.
- To compare the performance of control algorithms based on the first and second derivatives of the ORP signal.
Main Methods:
- A self-cycling fermentor was utilized, with toluene introduced via diffusion through a silicone membrane.
- Transient dissolved oxygen, carbon dioxide evolution, and oxidation-reduction potential (ORP) were monitored as potential control variables.
- Control algorithms were developed based on real-time estimates of the first and second derivatives of the ORP signal.
Main Results:
- Oxidation-reduction potential (ORP) was identified as the most effective control variable for toluene removal.
- Control based on the second derivative of the ORP signal achieved an average toluene removal efficiency of 95%.
- Control based on the first derivative of the ORP signal resulted in lower efficiencies (77%).
- The developed system demonstrated self-regulation, maintaining a high toluene removal rate (approx. 1.1 g/h) consistently across cycles.
Conclusions:
- A novel automated control scheme using the second derivative of the ORP signal significantly enhances toluene removal efficiency in cyclical bioreactors.
- The ORP signal, particularly its second derivative, provides a robust and effective means for real-time bioreactor control.
- The self-regulating system ensures consistent and high-performance toluene biodegradation, suitable for industrial applications.