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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

OECD 302B, Zahn-Wellens Test: 8.2 % degradation after 28 days - not inherently biodegradable  

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The biodegradation potential of Fe(Na)HBED was investigated according to OECD Guideline 302 B (Chojnacka, 2010). Activated sludge was used as inoculum and mixed with the test substance and mineral medium in 2 parallels. Further flasks were the procedure control (with the reference substance sodium benzoate), the inoculum blanks (each in 2 parallels) and one toxicity control (containing mineral medium, test substance, reference substance and inoculum). The suspended solid concentration was 0.3 g ss/L in each flask. The mixtures were agitated and aerated at 20 - 25 °C in the dark for a period of 28 days. The biodegradation process is monitored by determination of dissolved total organic carbon (DOC) with a spectrophotometer in filtered samples taken in daily intervals. The ratio of eliminated DOC, corrected for blank after each time interval, to the initial DOC value is expressed as the % biodegradation at the sampling time. The reference item attained 98 % degradation already after 14 days incubation, thereby fulfilling the validity criteria of the applied guideline, concluding that more or equal to 70 % degradation should have been occurred after 14 days. The test substance showed no toxic effects towards the used bacteria, since the toxicity control attained 55 % degradation after 28 days. The DOC content of the blank was below 10 mg/L at the start of the experiment. The test substance attained 3.2 % degradation after 14 days and 8.2 % degradation after 28 days, respectively. The test substance cannot be regarded as inherently biodegradable.