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Biodegradation in water: screening tests

Description of key information

The substance FAT 40841/A TE was found to be not readily biodegradable and not inherently biodegradable in guideline-conform GLP studies.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Two studies were performed following GLP to test the ready biodegradability and inherent biodegradability of the substance FAT 40841/A TE in accordance with EU Methods C.4-D and C.9. Activated sludge from a municipal wastewater treatment plant treating predominantly domestic sewage was used in the two tests. In the test on ready biodegradability, the biochemical oxygen demand (BOD) of the test item FAT 40841/A TE in the test media was in the normal range found for the inoculum controls. Consequently, FAT 40841/A TE was not biodegradable under the test conditions within 28 days. In the toxicity control, containing both FAT 40841/A TE and the reference item sodium benzoate, FAT 40841/A TE had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 102 mg/L. In the procedure controls, the reference item sodium benzoate was degraded by an average of 84% by Exposure Day 14, and reached an average biodegradation of 89% by the end of the test (Day 28), thus confirming suitability of the activated sludge.

In the test on inherent biodegradability, the mean concentration of DOC (dissolved organic carbon) in the flasks containing the test substance and inoculum did not significantly decrease during the exposure period of 28 days. Consequently, FAT 40841/A TE was not biodegradable under the test conditions. No significant DOC removal was observed during the first three hours of exposure which is an indication that the test item did not adsorb on activated sludge. The reference item diethylene glycol was ultimately and completely degraded by 100% within the first seven days of exposure, thus confirming suitability of the activated sludge. In the toxicity control, containing the test item, the reference item diethylene glycol and activated sludge (inoculum), the initial DOC decreased by 51% within 14 days of exposure. Thus, according to the test guidelines the test item was not inhibitory to activated sludge at the tested concentration of 309 mg/L because degradation was >35% within 14 days.