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Biodegradation in water: screening tests

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BIODEGRADATION IN WATER: SCREENING TESTS

The primary and inherent biodegradability were determined in the Zahn-Wellens-Test / EMPA Test with a non adapted activated sludge for the test itemDiethylenglykoldimethyletherover a period up to 36 days. The study was conducted from2010-03-08 to 2010-05-19with the definitive exposure phase oft the main test from 2010-04-13 to 2010-05-19according to OECD 302 B atDr.U.Noack-Laboratorien.

For the determination of the primary biodegradation the test item was tested at a concentration of 600 µg/L in duplicates. The primary biodegradation was determined by SPME GC/MS analysis of the test item. For the determination of the inherent biodegradation the test item was tested at a concentration of95 mg/Lin duplicates, corresponding to a DOC of51.3mg C/L in the test vessel. The inherent biodegradation of the test item was followed by determination of DOC. The ratio of eliminated DOC, corrected for the control at each time interval to the initial DOC value is expressed as the percentage biodegradation at each sampling date.

In order to check the activity of the test system diethylene glycole in a concentration of 120 mg/L was used as functional control. After 14 days a degradation rate of 100 % was reached.

The physico-chemical elimination (volatilisation) of the test item was monitored in separate sterile controls. At the test item concentration of95 mg/La sterile control without inoculum and poisoned with HgCl2was used. For determination of the primary biodegradation sterile controls (with inoculum and poisoned with HgCl2) with a test item concentration of 300 µg/L and 600 µg/L were tested. No physico-chemical elimination (volatilistion) occurred in the sterile controls until test end.

The primary degradation started after an adaptation phase of 16 days. The biodegradation was fast and on day 23 the pass level of 70 % was reached. After 28 days the primary degradation came to 95 %.

The inherent degradation started after a long lasting adaption phase of 21 days. The biodegradation was fast and the biodegradation reached the 70 % pass level after 29 days. After 36 days a biodegradation of 99 % was reached.

The test item is classified asprimary biodegradableafter 23 days
andinherent biodegradableafter 29 days.


Table 1:         Primary and Inherent Biodegradability of the Test Item Diethylenglykoldimethylether in Comparison to the Functional Control and the Sterile Control

Inherent Biodegradation / Elimination [%]

Day

7

14

21

28

36

test item
95 mg/L

0

3

4

67

99

functional control
120 mg/L

97

100

100

95

95

Sterile control*
95 mg/Ltest item

0

0

0

0

0

Primary Biodegradation / Elimination [%]

Test item
600 µg/L

9

01)

60

95

Sterile control*
600 µg/L test item

4

01)

0

2

Sterile control*
300 µg/L test item

0

01)

0

7

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria
Type of water:
freshwater

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