Biodegradation is an important process for the removal of many chemical substances in anaerobic environments. In methanogenic environments, this process involves dissimilation to carbon dioxide and methane.

This test method has been developed to screen organic chemicals for anaerobic biodegradation potential under methanogenic conditions, where there is no ingress of oxygen. A high-biodegradability result in this test method is good evidence that the test substance will be biodegradable in waste treatment plant anaerobic digesters and in many natural environments. Conversely, a low-biodegradation result may have causes other than poor biodegradability of the test substance. Inhibition of the microbial inoculum by the test substance may have occurred at the concentrations tested, or conditions in the test may have been inappropriate for the development of an acclimated microbial population. Toxicity should be suspected when the gas production in the blanks exceeds that in the test vessels. In such cases, further work is needed to assess the anaerobic biodegradation potential of the chemical. An estimate of the expected environmental concentration will help to put any observed toxic effects into perspective.

1.1 This test method covers screening procedures for the determining the biodegradation potential of organic chemicals under methanogenic conditions using an inoculum from anaerobic sewage treatment. The conditions described in this test method are not necessarily optimal for biodegradation, since it involves a dilute inoculum and a relatively high concentration of test chemical.

1.2 The test method is applicable to most organic chemicals, assuming that they can be accurately dosed into the test systems. The test is not applicable to chemicals that are inhibitory at the concentration used in the test or those whose volatility generates significant head pressure in the test vessels.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 8.