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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Activated sludge, OECD 301 B, CO2 Evolution Test: 0 % degradation after 28 days, not readily biodegradable 

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The biodegradability of the test substance was investigated according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test) by Clarke (2012). The study was conducted in compliance with the principles of Good Laboratory Practice (GLP). A mixed population of aquatic microorganisms (activated sludge) collected from an aeration tank of a wastewater treatment plant treating predominantly domestic wastewater was used as inoculum. A test concentration of 10 mg carbon/L was employed. Sodium benzoate (C6H5COONa) was used as reference substance.The test material plus the reference substance in inoculated culture medium to give a final concentration of 20 mg carbon/L to act as toxicity control. A blank (inoculated culture medium) was run in parallel. Each test vessel was inoculated with the prepared inoculum at a final concentration of 30 mg suspended solids (ss)/L.The study was conducted under aerobic conditions in a temperature controlled room at 21 °C, in darkness. Each CO2 and DOC (Dissolved Organic Carbon) analysis was carried out in triplicate. The pH was measured at the start and end of the test. Sodium benzoate attained 85 % degradation after 28 days thereby confirming the suitability of the inoculum and test conditions. The toxicity control attained 32 % degradation at the end of the test which confirms that the test material was not toxic to the sewage treatment microorganisms used in this experiment.

The test material attained 0 % degradation after 28 days and therefore cannot be considered to be "readily biodegradable" under the strict terms and conditions of OECD Guideline 301B. All validity criteria were fulfilled.