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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Not readily biodegradable (by OECD criteria). 

Key value for chemical safety assessment

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A modified sturm test was conducted to asses the ready biodegradability of the test substance. In this study, the biodegradability is determined by measuring the carbon dioxide formation in per cent of ThCO2 calculated from ThOC or TOC. The study was conducted according to EU guideline C.5 of 1984 (84/449/EEC), except for the following deviations: The volume of the test solution was reduced from 3.0 L to 1.5 L. The CO2 formed by biodegradation was absorbed with NaOH and determined on a carbon analyzer. Due to the poor solubility of the test substance in water, an emulsifier was used to achieve a better distribution in the medium. The test substance was added to the medium, which was then homogenized with Tween 80. As inoculum, bacteria collected from activated sludge of a sewage treatment plant were used. The test substance was tested in 2 concentrations: 10.8 mg/L and 21 mg/L. The duration of the test was 28 days, CO2 evolution was measured on days 5, 9, 13, 16, 19, 23, 27 and 28. The biodegradation was calculated as: 10.8 mg test substance/L: 27 % in 28 days, 21 mg test substance/L: 8 % in 28 days. It was therefore concluded that the test substance is partially biodegradable at a concentration of 10.8 mg/L. As the biodegradation rate for the test concentraion 21 mg/L did not exceed the 10 % level within 28 days, no biodegradation was observed (27 % after 28 days). The substance was thus evaluated to be moderately/party biodegradable (>20 % degradation after 28 days).