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1998 Progress Report: Innovations in Vapor Phase Bioreactor Design
EPA Grant Number: R826168Title: Innovations in Vapor Phase Bioreactor Design
Investigators: Kinney, Kerry A.
Institution: University of Texas at Austin
EPA Project Officer: Shapiro, Paul
Project Period: December 1, 1997 through November 30, 2000
Project Period Covered by this Report: December 1, 1997 through November 30, 1998
Project Amount: $293,809
RFA: Exploratory Research - Environmental Engineering (1997)
Research Category: Engineering and Environmental Chemistry
Description:
Objective:The objectives of the research project are (1) to develop an efficient vapor phase bioreactor that will operate reliably over long periods of operation and (2) to characterize the temporal and spatial distribution of active biomass in these bioreactor systems. Conventional bioreactor systems do not adequately control several important operating parameters such as biomass distribution, biomass activity and nutrient/moisture levels within the biofilm. These simple systems work acceptably during short-term tests in the laboratory but fail to ensure reliable long-term performance in the field where process variables fluctuate widely. Typically, these systems are analyzed from a black box approach and the activity of the biomass responsible for the pollutant degradation remains uncharacterized. In this study, the effect of three design features on bioreactor performance and biomass distribution and activity are being investigated: these features include directionally-switching operation, slip stream feed, and an aerosol delivery system. Progress Summary:
Four vapor phase bioreactors have been constructed and the effect of unidirectional and directionally switching operation on bioreactor performance has been assessed. Results indicate that directionally switching operation results in more stable performance than unidirectional operation at a constant toluene loading rate of 46 g/m3/hr. The directionally switching bioreactor yielded a relatively even distribution of biomass across the bioreactor column and maintained high microbial activity throughout the experimental period. In contrast, the unidirectional system accumulated excess biomass in the inlet half of the bioreactor, resulting in increased pressure drop, a decline in microbial activity and, eventually, contaminant breakthrough. Despite a low biomass yield coefficient, biomass slowly accumulated in both systems. However, the pollutant degradation capacity remained high in the DS system despite the biomass accumulation because the biomass was more evenly distributed throughout the bioreactor column.
Characterization of the biomass activity in the vapor phase bioreactors indicates that unidirectional operation results in a skewed distribution of active biomass with the highest activity near the inlet and virtually no activity in the outlet sections. As excess biomass accumulated in the unidirectional system, inactivation of the biomass proceeded from the inlet section to the outlet section. In addition, the specific microbial activity (i.e., respiratory activity per unit biomass) was found to be generally higher in the DS system than in the UD bioreactor. However, the toluene-degrading fraction of the total microbial population slowly decreased in both bioreactors following start-up.
The effect of the nutrient supply on bioreactor operation has also been assessed. The initial nitrogen supply was found to have a significant effect on the acclimation period required by the bioreactor following start up. In addition, the delivery efficiency of the nutrient aerosol system has been determined.
Finally, a fungal vapor phase bioreactor has been developed that degrades toluene contaminated air. Studies are underway to investigate degradation kinetics and biomass accumulation in this new type of vapor phase bioreactor.
Future Activities:Future activities will focus on developing and optimizing the slip feed design feature as well characterizing the activity and distribution of the biomass in the bioreactor system. In addition, the capabilities of the fungal vapor phase bioreactor will be assessed and different design configurations will be investigated. Journal Articles:
No journal articles submitted with this report: View all 16 publications for this project
Supplemental Keywords:Fungal bioreactor, biomass activity , Air, Scientific Discipline, Engineering, Chemistry, & Physics, air toxics, Environmental Engineering, Environmental Chemistry, treatment, biomass, chemical treatment, biofilms, environmental contaminants, biotrickling filters, air sampling, airborne suspension, atmospheric particles, emission control technologies, cost effective, biofiltration systems, VOCs, vapor phase bioreactors, directionally-switching parameters
Progress and Final Reports:
Original Abstract
1999 Progress Report
Final Report