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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The test substance is not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The testsubstance was investigated for its ready biodegradability in a manometric respirometry test over 28 days based on EU Commission Directive 92/69 EEC, C.4-D (1992) and OECD Guideline for Testing of Chemicals No. 301 F (1992). Additionally, the BOD5 (biochemical oxygen demand after 5 days) was recorded.

The biochemical oxygen demand (BOD) of the testsubstance in the test media was in the normal range found for the inoculum controls. Consequently, the test substance was found not to be biodegradable under the conditions of the test within 28 days. In the toxicity control, containing both the test substance and the reference item sodium benzoate, no inhibitory effect on the biodégradation of the reference item was determined. Thus, the testsubstance had no inhibitory effect on the activity of activated sludge microorganisms. In the procedure control, the reference item sodium benzoate was degraded by 88% on exposure Day 14, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the degradation of the reference item displayed still the same value of 91%. The chemical oxygen demand (COD) of the testsubstance was determined to be 0.82 mg O2/g test material. After the test duration of five days, a very low oxygen consumption was determined in the two flasks containing the test substance, which was in the normal range of the inoculum controls. Thus, the BOD5 (biochemical oxygen demand after 5 days) can be stated as follows: BOD5 = 0 mg O2/mg test item

The testsubstance was investigated for its inherent biodegradability in a manometric respirometry test over 28 days based on the OECD Guideline for Testing of Chemicals No. 302 C (1981). The following modifications were made: activated sludge from one source was used, the activated sludge was not fed during the holding period of maximum seven days, the test was run at 22 °C, the test water composition was slightly changed, and only the biological oxygen demand (BOD) was monitored, no test nem specific analysis was performed.

The percent biodegradation of the test item was calculated based on the theoretical oxygen demand of 1.13 mg O2/mg testsubstance without nitrification (ThODNH4) and 1.90 mg O2/mg test item with nitrification (ThODNO3). The biochemical oxygen demand (BOD) of the testsubstance in the test media was in the range of the inoculum controls. Consequently, the test substance was not biodegradable under the test conditions within 28 days. No significant degradation of the test item occurred in the abiotic control under the test conditions within 28 days. In the toxicity control, containing both the test substance and the reference item sodium benzoate, the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 50 mg/L. In the procedure controls, the reference item (sodium benzoate) was degraded by an average of 65% and 78% by Exposure Days 7 and 14, respectively, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 86%.