Date of Award
Doctor of Philosophy in Environmental Science - (Ph.D.)
Chemical Engineering, Chemistry and Environmental Science
Piero M. Armenante
This study investigated the possibility of simultaneous removal of vapors of dissimilar volatile organic compounds from air streams in a biotrickling filter (BTF). Using a rricrobial consortium known to utilize ortho-dichlorobenzene (o-DCB) as sole carbon and energy source, a culture was developed on o-DCB/ethanol mixtures and a BTF unit was developed and operated with air streams carrying o-DCB and ethanol vapors. Simultaneous removal of the two compounds was observed in experiments that span a period of over three years.
Experiments were performed at air residence times ranging from 4 to 6.5 min, liquid flow rates from 3.6 to 9 Lh-1, and inlet air concentrations from 0.85 to 4.5 gm-3 and 0.95 to I I gM-3 for o-DCB and ethanol, respectively. The maximum removal rate was 40 and 150 gm-3 packing h-1 for o-DCB and ethanol, respectively. It was possible to duplicate results in experiments performed under a given set of operating conditions at time intervals as far as 9 months apart from one another.
The presence of the readily degradable ethanol at relatively high concentrations led to the formation of significant amounts of biomass in the liquid recirculating through the BTF resulting in the removal of o-DCB and ethanol both in the liquid phase and the biomass attached to the packing material. The readily biodegradable ethanol led to better coverage of the packing with b1ofilm, resulting in a positive effect on the removal of o-DCB vapor. However, every four months an abrupt increase in pressure drop build-up and concornitant loss in BTF performance was observed over a 5-day period. Once excess biomass was removed from the BTF unit, normal operation was recovered within 3-4 days.
Steady state operation of the unit was mathematically described with a model involving mass balances for o-DCB, ethanol, and oxygen in three phases: air, recirculating liquid, and biofilm. The model accounts for reaction in both the liquid and biofilm phases. Through the introduction of the notion of effectiveness factors for o-DCB and ethanol, the equations for the b1ofilm were decoupled from those for the air and liquid allowing for easier numerical solution of the original complex model. The model was found capable of predicting the data on removal rates with a less than 10% - and oftentimes less than 5% error.
Independent kinetic experiments led to the following conclusions: o-DCB and ethanol were biodegraded following Andrews self-inhibitory kinetics; no kinetic interactions occurred over the concentration ranges tested in the BTF; there was no biomass diversification along the length of the BTF unit.
Bhattacharya, Suchismita, "Simultaneous removal of ortho-dichlorobenzene and ethanol vapors in a biotrickling filter : experimental results and process modeling" (2001). Dissertations. 512.