Optimization of Transient Response of Vapor Phase Biofiltration Systems

EPA Grant Number: R825390
Title: Optimization of Transient Response of Vapor Phase Biofiltration Systems
Investigators: Schroeder, Edward D. , Chang, Daniel Y.
Institution: University of California - Davis
EPA Project Officer: Shapiro, Paul
Project Period: November 1, 1996 through October 30, 1998
Project Amount: $168,012
RFA: Exploratory Research - Air Engineering (1996) RFA Text |  Recipients Lists
Research Category: Land and Waste Management , Air , Engineering and Environmental Chemistry

Description:

Three problems will be addressed in this study of management of transient loadings: (1) management of diurnal transients, (2) management of periodic transients, and (3) management of compositional transients. Diurnal transients are those that occur on a regular basis due to overnight and weekend closures. Periodic transients result from spills or other large inputs of VOCs. Compositional transients result from changes in the make-up of the contaminant mixture. Contaminants use will include toluene, dichloromethane, and gasoline. All three contaminants have been extensively used in previous research by our group. The experimental systems will be 1 m deep, 0.15 m I.D. columns similar to those used in previous studies at UC Davis. Air flux will be maintained at 1m3/m2omin and VOC concentrations and mixtures will be varied with the type of experiment. Packing media will be commercially available ceramic, diatomaceous earth pellets. Only concentration transients need to be addressed because air flow to the beds can be positively controlled for systems such as soil vapor extraction units and industrial sources generally have constant flow fans controlling exhaust streams. The diurnal transient experiments will be structured as on-off studies with variable peak to mean ratios and variable off periods. Air and VOCs will be passed through the columns during the on periods while only air will be fed during the off periods. Two approaches to diurnal loading will be used: (1) constant feed concentration, decreasing average loading, and (2) constant average loading, increasing feed concentration. Rapidly responding cultures are expected to develop which react quickly to feed on periods. As an alternative a slipstream feed will be considered to keep microorganisms active. Periodic transient loading response will be studied using VOC spikes. We propose to investigate a directional switching flow feed strategy to enhance the distribution of active biomass throughout the length of the biofilter bed as a management strategy for controlling breakthrough. In this operation, the biofilter will be fed from the top of the column for a set period of time and the inlet will then be switched to the bottom of the column. In this way, a more even distribution of active biomass should result and the response of the biofilter to transients improved. Compositional transient studies will be divided into two segments: (1) investigation of the mechanism of competition in cases where different microbial groups are involved, and (2) investigation of the removal of more recalcitrant compounds in VOC mixtures where the principal microbial groups are believed to be the same. The case where different microbial groups are involved will be modeled using toluene and dichloromethane as the VOCs while gasoline will be used for the study of mixtures degraded by the same groups of microorganisms. As in the case of diurnal and periodic transients, a mitigation strategy is proposed.

Publications and Presentations:

Publications have been submitted on this project: View all 2 publications for this project

Supplemental Keywords:

Scientific Discipline, Air, Toxics, POLLUTANTS/TOXICS, Ecology, air toxics, Environmental Chemistry, Chemicals, HAPS, VOCs, Engineering, 33/50, Engineering, Chemistry, & Physics, transient response, gasoline, vapor extraction, Toluene, ceramic packing, diurnal loading, biomass, vapor phase, soil, dichloromethane, biofiltration systems, exhaust

Progress and Final Reports:

  • 1997 Progress Report
  • Final