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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:
01 Mar - 28 Mar 1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Reference:
Composition 1
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
GLP compliance:
no
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: laboratory culture
- Laboratory culture: yes; activated sludge from a laboratory culture. Wastewater from a domestic sewage treatment plant was used for the culture. Activated sludge for the study was taken on 29 Feb 1996.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 20 ± 1 °C
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 3
- Measuring equipment: respirometer recording O2 consumption

SAMPLING
- Sampling method: direct measurement from respirometer

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 3 bottles
- Abiotic sterile control: no
- Toxicity control: yes, 2 bottles
- Other: reference substance: yes, 3 bottles
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
71
Sampling time:
28 d
Remarks on result:
other: Mean of three replicates
Details on results:
71% degradation was observed after 28 d. Since the 10-day window was not met, the substance is not readily biodegradable according to the OECD criteria.
Results with reference substance:
77% (mean) after 28 d, 60% pass level was reached.

Table 1: Degradation of the test substance

 

 

Day of sampling

 

Replicate

4

6

8

12

14

18

20

22

26

28

Corrected BOD [mg O2/L]

1

1

1

3

70

92

124

137

149

177

182

2

8

8

17

83

104

131

143

152

176

186

3

2

8

21

94

134

168

180

191

218

231

% degradation

1

0

0

1

25

33

44

49

53

63

65

2

3

3

6

30

37

47

51

54

63

66

3

1

3

8

34

48

60

64

68

78

82

% degradation (mean)

-

1

2

5

30

39

50

55

58

68

71

Conclusion in the test report is not correct. In the test report the substance is considered to be "readily biodegradable". However, the 10-day window was not considered for this final conclusion.

The toxicity control attained 43% degradation after 14 d indicating that the test substance is not inhibitory to the inoculum.

Validity criteria fulfilled:
yes
Interpretation of results:
other: biodegradable, but failing the 10-day window
Conclusions:
The test substance is biodegradable, but failing the 10-day window. Moreover, the inoculum is not inhibitory to the inoculum as the toxicity control attained 43% degradation within 14 d.

Description of key information

The substance cannot be considered as readily biodegradable, because the 10-day window was not passed (71% after 28 d; O2 consumption; EU Method C.4-D)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

One experimental study is available investigating the ready biodegradability of the test substance. The study was performed according to the EU Method C.4-D. Activated sludge from a municipal sewage treatment plant was used as inoculum. 71% degradation of the test substance was recorded based on O2 consumption after 28 d. Since the 10-day window was not met the test substance is considered to be not readily biodegradable. The toxicity control (containing both, reference substance and test substance) attained 43% after 14 d. Thus, the test substance is not considered to be inhibitory to the inoculum.