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Environmental fate & pathways

Biodegradation in water: screening tests

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The ready biodegradability of the test item Basic Red 76 was determined with a non-adapted activated sludge over a test period of 28 days in the modified Sturm Test. The study was performed according to OECD guideline 301B. The test item was tested at a concentration of 25 mg/L with 2 replicates corresponding to a carbon content (TOC) of 10.8 mg C/L in the test vessels. The test vessels were incubated at low light conditions and at a temperature of 22 +/- 2 deg C. The biodegradation of the test item was followed by titrimetric analysis of the quantity of CO2 produced by the respiration of bacteria. The degradation was terminated on day 28 by acidification of the test solutions. The last titration was performed on day 29 after residual CO2 had been purged from the test solutions over a period of 24 hours. The percentage CO2 production was calculated in relation to the theoretical CO2 production (ThCO2) of the test item. The biodegradation was calculated for each titration time. Sodium benzoate was used as functional control to check the activity of the test system. The percentage degradation of the functional control reached the pass level of 60% within 6 days and a maximum biodegradation of 96% on day 28. In the toxicity control containing both test and reference items a biodegradation of 30% was determined within 14 days and a biodegradation of 33% after 28 days. The biodegradation of the reference item was not inhibited by the test item in the toxicity control. Both test item replicates did nor reach the 10% level (beginning of biodegradation) within the 28 day period of the study. The mean biodegradation on day 28 was 3%. Under the test conditions the test item is classified as not readily biodegradable within the 28 day period of the study.

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