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Testimonials

“We have found the performance of the system to be quite satisfying and user friendly. We are currently running low level O2 uptake experiments and are impressed with the sensitivity of the instrument.”

Wendy Segal
Research Technician
BetzDearborn Division of Hercules, Inc.
Trevoset, PA

“I have found the performance of the Challenge AER-200 to be unmatched. The precise measurement of oxygen consumption, homogenous mass transfer of test materials, and constant and consistent operating temperature have enabled me to obtain extremely accurate test results, particularly as compared to other respirometer systems. I find the Challenge system to be extremely user friendly.”

Randy Drake
Senior Biologist
River Bend Labs
St. Louis, MO

Standardized Biodegradation Protocols

Standardized Biodegradation Protocols Graph

A number of protocols have been developed to standardize evaluations of the biodegradability of specific compounds or formulations (ISO 9408, 1999; OECD 301, 1992; USEPA 835, 1998). These protocols usually involve long-term (14 to 28+ day) respirometer testing to evaluate the extent to which a compound is oxidized relative to its theoretical oxygen demand (THOD) or measured COD. These test protocols usually involve the following steps:

  1. Add 100 mg/L of test organic, or no less than 100 mg/L THOD (or COD), to a test respirometer vessel.
  2. Add no more than 30 mg VSS/L as a seed culture.
  3. Run simultaneous tests with a reference compound (usually analine, benzoate, or acetate).
  4. Measure oxygen uptake for 28 or more days and compare to THOD or TCOD.
  5. Oxygen uptake of 60% or more of THOD or COD in 28 days shows acceptable biodegradability.

An example of tests for an organic-based cleaning agent using aniline as a reference compound is shown in the figure below. The test revealed the following:

  1. Biodegradation of the test product began earlier than the control (aniline), thereby indicating that no acclimation was required.
  2. The fact that the oxygen uptake curves for the two test doses were the same indicated that the test compound was not toxic.
  3. The fact that the oxygen uptake for the test compound exceeded 60 % of the THOD in 28 days indicates that the formulation was readily biodegradable.
  4. The fact that the oxygen uptake for the test compound was only 65% of the theoretical after 28 days of incubation implies that one or more constituents were not biodegradable.