Anaerobic biodegradation potentials in digested sludge, a freshwater swamp and a marine sediment

An anaerobic gas production test was used for determining the potential biodegradation of 22 organic chemicals under methanogenic conditions. Nine of the examined chemicals were extensively mineralized (> 75%) both in sewage sludge and in a freshwater swamp indicating good agreement between biodegradation potentials in these habitats. Samples from a marine sediment showed a less extensive mineralization of most of the test chemicals, and lag periods of several weeks often preceded net gas production. As marine sediments usually contain sulfate at the time of collection, the assessment of biodegradation potentials in such environments is probably more reliable when using a method based on sulfate reduction instead of methanogenic gas production. The results of the tests indicate that the commonly recommended washing of sludge solids can be eliminated by applying a more diluted inoculum.