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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The readily biodegradation of the test item was determined in a study according to the OECD guideline 301 D. The degradation was determined to be 75 % after 28 days. In a second supporting OECD guideline study the degradation was determined to be 97 % after 28 days. Both studies met the 10-d window criteria. According to this result the substance is readily biodegradable in water. 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Key

The study was conducted according with the OECD Guideline 301 D "Ready Biodegradability: Closed Bottle Test" (1989). In the closed bottle test, a test compound is added to an aqueous solution of mineral salts and exposed to a relatively low number of microorganisms under aerobic conditions for 28 days. Activated domestic sludge was used as inoculum. The inoculum was taken from an activated sludge plant and then preconditioned to reduce the endogenous respiration rate. As preconditioning, the sludge (200 mg dw/L) was aerated for one week. This sludge was diluted to a sludge concentration in the BOD bottle of 2 mg dw/L. After 28 days the test substance showed 75% degradation, compared to the control which showed 82% degradation. The 10-d window criteria was met: the degradation at day 1 was 10% and at day 11 it was 69%. The substance is readily biodegradable.

Supporting

The second study was conducted according to OECD Guideline 301 D "Ready Biodegradability: Closed Bottle Test". The inoculum was taken from an activated sludge plant, the municipal waste water treatment plant. The sludge was preconditioned during a week: a sludge suspension of 1 g/L was aerated in the dilution water. The modification was introduced to reduce high residual respiration rate. The results showed a degradation of 90% after 2 weeks and 97% after 4 weeks for the test substance. The 10-d window criteria was met. The substance is readily biodegradable.