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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000-01-27 till 2000-03-07
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
July 17, 1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
December 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum: sewage plant Groß-Zimmern, Germany
Conditioning: The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centri-fuged. This procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 4 g dry material per litre were mixed with test water and then aerated until use. Before use the sludge was filtered through cotton wool.
Duration of test (contact time):
28 d
Initial conc.:
2.94 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: reconstituted water according to OECD 301
- Additional substrate: no
- Test temperature: 22 °C
- pH: 7.6 (measured at the start of the test)
- pH adjusted: no
- Aeration of dilution water: yes
- Continuous darkness: yes
- Oxygen Concentration of Test Water: 8.6-8.9 mg O2/L (measured at the start of the test)

TEST SYSTEM
- Culturing apparatus: Karlsruher flasks of 250 mL volume with glass stoppers
- Number of culture flasks/concentration: 2
- Measuring equipment: O2-electrode (WTW Oxi 340, Wissenschaftlich Technische Werkstatten GmbH, Weilheim, Germany)
- Test performed in closed vessels due to significant volatility of test substance: yes

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculum and test medium
- Procedure control: reference item, inoculum and test medium
- Toxicity control: test item, reference item, inoculum and test medium
Reference substance:
aniline
Key result
Parameter:
% degradation (O2 consumption)
Value:
-2
Sampling time:
28 d
Details on results:
Under the test conditions the percentage biodegradation of the test item reached in the mean -2 % after 28 days of incubation.
In the toxicity control containing both, the test item and the reference item Aniline, in the mean 39 % biodegradation was noted within 14 days and 44 % biodegradation after 28 days of incubation.
Results with reference substance:
The reference item Aniline was sufficiently degraded to in the mean 82 % after 14 days, and to 107 % after 28 days of incubation.

Table 1: Percentage biodegradation at different time intervals during the exposure of 28 days

Treatment

Conc. (mg/L)

Flask No.

% biodegradation after n days of exposure

2

5

7

12

14

21

28

Test item

2.94

1a

-2

-3

-3

-4

-3

-4

-2

1b

-2

-3

-3

-4

-5

-2

-2

mean

-2

-3

-3

-4

-4

-3

-2

Procedure Control (Aniline)

2.02

2a

2

54

61

76

81

101

105

2b

4

54

63

80

83

103

109

mean

3

54

62

78

82

102

107

Toxicity control

TS: 2.94 Aniline; 2.02

4a

n.d.

n.d

29

n.d.

39

38

43

4b

n.d.

n.d.

29

n.d.

39

38

45

mean

n.d.

n.d.

29

n.d.

39

38

44

n.d. not determined

TS: test item

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test item is not biodegradable in a test according to OECD 301 D.
Executive summary:

The test item was tested for its ready biodegradability in the closed bottle test at 2.94 mg/L. The study procedure was based on EU Method C.4-E and OECD guideline No. 301 D. The test item was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item Aniline was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed no significant (0%) degradation. Since all acceptability criteria prescribed by the protocol were met, this study was considered to be valid. In conclusion, the test item was not biodegradable under the conditions in the closed bottle test presently performed.

Description of key information

The test item is not biodegradable in a test according to OECD 301 D (reference 5.2.1 -1).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

The test item was tested for its ready biodegradability in the closed bottle test at 2.94 mg/L. The study procedure was based on EU Method C.4-E and OECD guideline No. 301 D. The test item was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item Aniline was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed no significant (0%) degradation. Since all acceptability criteria prescribed by the protocol were met, this study was considered to be valid. In conclusion, the test item was not biodegradable under the conditions in the closed bottle test presently performed (reference 5.2.1 -1).