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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:
1999-04-30 to 1999-05-28
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):secondary effluent of a domestic sewage treatment plant (Kläranlage Odenthal)
- Laboratory culture: none
- Pretreatment: separation of coarse particles by filtration
- Concentration of sludge: 5 mL/L
- Method of cultivation: aeration for 7 days
Duration of test (contact time):
28 d
Initial conc.:
3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium
- Test temperature: 20 °C
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: flasks
- Number of culture flasks/concentration: 10
- Other: The test substance is suspended in a mineral medium, inoculated with a mixed population of aquatic microorganisms and incubated for 28 days under aerobic conditions in the dark at 20 +/-1°C. During this period, the biodegradation of the test substance is determined on the basis of the reduction of dissolved oxygen.

SAMPLING
- Sampling frequency: 0, 7, 14, 21 and 28 d

CONTROL AND BLANK SYSTEM
- Inoculum blank: 10 flasks/ concentration
- Toxicity control: yes

Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
65
Sampling time:
28 d
Remarks on result:
other: mean value

Dissolved oxygen depletion

 

 

 

                      Dissolved oxygen depletion after n days [mg/l]

 7 d   

 14 d 

 21 d   

 28 d   

 DO [mg/l]

 Degradation %

 DO [mg/l]

 Degradation %

 DO [mg/l]

 Degradation %

 DO [mg/l]

 Degradation %

Test substance: 3.0 mg/l; ThOD:2335 mg/g

Replicate 1

 2.86

 41

 3.89

 56

 4.63

 66

 4.51

 64

Replicate 2

 2.98

 43

 4.12

 59

 4.56

 65

 4.54

 65

Mean

 

 42

 

 58

 

 66

 

 65

Reference substance: 2.9 mg/l; ThOD:1665 mg/g

Replicate 1

 3.29

 68

 3.77

 78

 4.05

 84

 4.08

 84

Replicate 2

 3.05

 63

 3.82

 79

 4.10

 85

 4.18

 87

Mean

 

 66

 

 79

 

 85

 

 86

Toxicity control*

Replicate 1

 7.14

 60

 8.38

 71

 8.79

 74

 8.88

 75

Replicate 2

 7.20

 61

 8.25

 70

 8.45

 71

 8.86

 75

Mean

 

 61

 

 71

 

 73

 

 75

*In the toxicity control 3.0 mg/l test substance and 2.9 mg/l reference substance were used. The ThOD values respectively COD values of these substances are shown in the table above. Toxicity control: Test substance not inhibitory at tested concentration of 3.0 mg/L.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradation of Ethyl isovalerate was determined according to OECD 301 D and under GLP conditions. The test substance showed a biodegradation for at least 65% within 28 days of incubation at the tested concentration of 3.0 mg/L. The pass level of 60% degradation was reached in a 14-d window. Therefore, the test substance was classified as "readily biodegradable" according to OECD criteria.

Description of key information

Readily biodegradable: 65% within 28 days (O2 consumption, OECD 301 D).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation of Ethyl isovalerate was determined according to OECD 301 D and in compliance with GLP. The test substance showed a biodegradation of 65% within 28 days of incubation at the tested concentration of 3.0 mg/L and reached the pass level of 60% degradation in a 14-d window. Furthermore, no inhibitory effects on microorganisms were observed up to 3 mg/L. The test substance was therefore classified as readily biodegradable according to OECD criteria.