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Environmental fate & pathways

Biodegradation in water: screening tests

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The biodegradation of 200 mg test item per litre (164 mg/L ThOD, concentration [1]) in the static test was found to be at average 58 % (53 and 64% in replicate vessels). A plateau was not yet reached on day 28. On day 28, concentration (2) (72 mg/L test substance, 59 mg/L ThOD) showed lower biodegradation values, average 52% (47 to 58% in replicate vessels). A plateau was not yet reached after 28 days. The 10% generic trigger value for biodegradation initiation was reached within latest 2 days after test initiation. Within the day 10 -window, average 49% and 44% biodegradation occurred, respectively. The degradation of the reference substance sodium benzoate had reached average 88 % (87% and 90%) within the first 14 days. The difference of extremes of replicate values of the removal of the test item was less than 20% at the end of the test for 200 mg/L and 72 mg/L, respectively. Therefore, the test is valid. No inhibitory effects of the test item were observed in the toxicity control where more than 25 % degradation occurred within 14 days. In conclusion, the substance is not readily biodegradable. However, with average 58% of biodegradation, the trigger value of 60% was only marginally failed, whereas one of the two replicates reached 64% biodegradation.

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[Type of water: freshwater]

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