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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:
1991-12-12 to 1992-01-09
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: According to OECD 301 D (1981) and GLP, no toxicity control performed
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes
Test material information:
Composition 1
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Stored in darkness
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): Effluent from the waste water treatment plant KA Hochdahl, Germany
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Initial conc.:
5 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±1°C

TEST SYSTEM
- Culturing apparatus: Conical shoulder bottles
- Number of culture flasks/concentration: Two flask per concentration, two flask per reference and inoculum control, oxygen control with one flask
- Measuring equipment: Jodometric determination of oxygen.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: No
- Toxicity control: No
- Other: Oxygen control (medium without test substance and inokolum) and reference control (sodium benzoate)
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
68
Sampling time:
28 d
Remarks on result:
other: test concentration: 2 mg/L
Key result
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
28 d
Remarks on result:
other: test concentration: 5 mg/L
Details on results:
No toxicty control was included. However, it could be observed that the substance had no inhibitory effects to the microorganisms up to a test concentration of 5 mg/L.
Results with reference substance:
In parallel preparations with reference substance, a biodegradation of 90% was achieved within 28 days.

DO, mean after n days in [mg O2/L]

 

7

14

21

28

Test substance I*

[c=2 mg/L]

7.11

6.66

6.39

6.47

Test substance II*

[c=5 mg/L]

5.30

3.39

3.04

2.65

Reference substance*

6.41

6.38

6.18

6.17

Blank inoculum*

9.12

9.18

9.26

9.18

*mean of 2 values

Biological degradation (closed bottle test)

Concentration

(mg/L)

% O2-consumption after days (d)

 

 

7

14

21

28

Test substance

2

51

64

72

68

5

39

58

63

66

Sodium benzoate

2

81

84

92

90

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradation of the test substance was determined in a closed bottle test according to OECD 301 D and GLP. Between 66 and 68% of the test substance was biodegraded within 28 days. No toxicty control was included. However, it could be observed that the substance had no inhibitory effects to the microorganisms up to a test concentration of 5 mg/L. The test substance was, therefore, classified as readily biodegradable according to OECD criteria.

Description of key information

Readily biodegradable: 66 - 68% within 28 days (O2 consumption, OECD 301 D)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation of the test substance was determined in a closed bottle test according to OECD 301 D and GLP. Between 66 and 68% of the test substance was biodegraded within 28 days. No toxicty control was included. However, it could be observed that the substance had no inhibitory effects to the microorganisms up to a test concentration of 5 mg/L. The test substance was, therefore, classified as readily biodegradable according to OECD criteria.