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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The test material is considered to be readily biodegradable, with a mean degradation of 84.4 % after 28 days, OECD 301D, EPA OPPTS 835.3110, EU Method C.4-E, Sipos (2013a).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In the key study (Sipos, 2013a) the test material was investigated for its ready biodegradability in a closed bottle test over a period of 28 days. The study was performed under GLP conditions and in accordance with the standardised guidelines OECD 301 D, EU Method C.4 E and EPA OPPTS 835.3110.

The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. Samples were incubated for 28 days in the dark with the test material at 3.1 mg/L. The test system was a microbial inoculum collected from the sewage plant for domestic sewage. The sludge was washed by centrifugation filtered through cotton wool and aerated until use. Based on the determined dry weight content, the washed sludge suspension contained 4 g dry material per litre.

Sodium benzoate was used as a procedural control, tested simultaneously under the same test conditions. Results confirmed the suitability of the activated sludge inoculums.

Under the test conditions the percentage biodegradation of test material reached a mean of 84.4 % after 28 days based on the measured COD of the test material. According to the test guidelines the pass level for ready biodegradability, 60 % of COD and this level has to be reached in a 10-day window within the 28-day period of the test. However taking into account that the test material was sufficiently degraded to a mean of 68.4 % after 14 days and according to the test guideline the value obtained in a 14-day window is acceptable in the used method, therefore the test material can be considered to be ready biodegradable.

In the toxicity control containing both, the test material and the reference substance (sodium benzoate), a mean of 46.7 % biodegradation was noted within 14 days and 54.7 % biodegradation after 28 days of incubation. According to the test guidelines the test material can be assumed to be not inhibitory at the applied concentration level of 3.1 mg/L on the activated sludge microorganisms because degradation was >25 % within 14 days.