Comparison of Methods for Determining Biodegradation Kinetics of Volatile Organic Compounds

Regulations, such as the Synthetic Organic Manufacturing Industry Hazardous Organic National Emission Standards for Hazardous Air Pollutants (SOCMI-HON) rule of the recently promulgated Clean Air Act Amendments, target the reduction of emissions of volatile organic compounds (VOCs) from industrial sources including process vents, tanks, equipment leaks, and wastewater. As required by the regulation, Method 304 was used to measure the VOC biodegradation kinetics, which were then used to determine the degree of biodegradation versus air stripping. In addition to Method 304, batch tests that use oxygen addition (BOX tests) and serum bottle (SB) tests were used to determine the biodegradation kinetics of ethylene oxide (EO) and acetaldehyde (AA) in a chemical plant. The Method 304 first-order rate constant was measured to be 0.99 L/g·h and 0.24 L/g·h for EO and AA, respectively. Linearized first-order rate constants from the BOX and SB tests were greater than the Method 304 rate constants by at least an order of magnitude. Also, the BOX tests and SB test kinetics correctly predicted full-scale bioreactor emissions, whereas the Method 304 kinetics did not.