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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The test item is not readily biodegradable  within the 28 day period of the study.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The ready biodegradability of the test item Disperse Blue CVG was determined with a non-adapted activated sludge over a test period of 28 days in the Modified Sturm Test. The test item was tested at a concentration of 21 mg/L with 2 replicates corresponding to a carbon content (TOC) of 10.4 mg C/L in the test vessels.The test vessels were incubated at low light conditions and at a temperature of 21 – 24 °C.

The biodegradation of the test item was followed by titrimetric analysis of the quantity of CO2produced by the respiration of bacteria. The degradation was stopped on day 28 by acidification of the test solutions. The last titration was made on day 29 after residual CO2 had been purged from the test solutions over a period of 24 hours. The percentage CO2production was calculated in relation to the theoretical CO2 production (ThCO2) of the test item. The biodegradation was calculated for each titration time.

 

To check the activity of the test system sodium benzoate was used as functional control. The percentage degradation of the functional control reached the pass level of 60 % within 6 days and a biodegradation of 87 % after 28 days.

In the toxicity controlcontaining both test and reference item a biodegradation of 44 % was determined within 14 days and it came to 52 % after 28 days. The biodegradation of the reference item was not inhibited by the test item in thetoxicity control.

The biodegradation of the test item is copmared to the readily degradable functional control and the toxicity control. Both test item replicates did not reach the 10 % level (beginning of biodegradation) until day 28 end. The 60 % pass level was not reached until test end. The mean biodegradation on day 28 was 4 %.

 

 

The test item is classified as not readily biodegradable within the 28 day period of the study.

 

 

Biodegradation of the Test Item Disperse Blue CVG in Comparison to the Functional Control and the Toxicity Control

 

Biodegradation [%]

 

Study Day [d]

 

6

14

21

28

Test Item, 1stReplicate

2

4

4

5

Test Item, 2ndReplicate

1

2

2

3

Functional Control

64

82

85

87

Toxicity Control
test item + reference item

28

44

49

52