Project at a Glance

Title: Biofilter technology for NOx control.

Principal Investigator / Author(s): Hudepohl, Schroeder, Chang

Contractor: UC Davis

Contract Number: 96-304

Research Program Area: Emissions Monitoring & Control

Topic Areas: ICAT Grants / Technology, Stationary Sources, Toxic Air Contaminants


Little attention has been given to the transformation of nitrogen compounds in vapor phase biofilters. Both production and removal of oxides of nitrogen (NOx) have been demonstrated in laboratory experiments in the Center for Environmental and Water Resources Engineering at the University of California, Davis. Thus there is a potential that under certain operating conditions NOx may be emitted from biofilters designed to remove volatile organic compounds from contaminated air. Additionally it appears possible to design and operate biofilters for the purpose of removing NOx from contaminated air. The number of new companies offering biofilters as economical air pollution control devices for treatment of air contaminated with volatile organic compounds is rapidly growing. Many companies are seeking to apply biofilters to relatively high concentrations, several hundreds to the thousand - ppm, range. Locally anaerobic conditions in which nitrous oxide (N2O) and nitric oxide (NO) are produced and released to the atmosphere can occur. On the other hand, it appears possible to design biofilters for the aerobic oxidation of N2O and NO to NO3 or the anaerobic reduction of N2O and NO to N2. The potential of biological processes for NOx control appears to be considerable.

The specific objectives of this project were:

1. To determine whether significant emission of nitrogen containing compounds such as NH3, N2O, NO or NO2 occur during normal and / or "upset" biofilter operations.
2. To determine if oxidation of N2O and NO to NO3 can be carried out in biofilters using microbial nitrification.
3. To develop operating parameters for promoting control of NOx using local anaerobic denitrification and contaminated air feed stock.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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