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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:
09 Aug - 06 Sep 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: Secondary effluent of a domestic sewage treatment plant
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Secondary effluent was collected at "Kläranlage Odenthal", Germany on 04 Aug 2000.
- Pretreatment: Coarse particles were separated by filtration; aeration of mineral medium plus inoculum for 5 d
Duration of test (contact time):
28 d
Initial conc.:
2.9 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
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Test performed in closed vessels due to significant volatility of test substance: yes (completely full and closed bottles)
- Test performed in open system: no

SAMPLING
- Sampling frequency: Dissolved oxygen was measured after 0, 7, 14, 21 and 28 d

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2 bottles
- Abiotic sterile control: no
- Toxicity control: yes, 2 bottles
- Other: reference subtance: yes, 2 bottles
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
73
Sampling time:
28 d
Remarks on result:
other: Mean of two replicates.
Results with reference substance:
The reference substance showed 76% (mean) degradation after 14 days and was degraded to 89% (mean) after 28 d.

Table 1: Degradation of the test item, the toxicity control and the reference item during exposure

 

% degradation of the test item

7 d

14 d

21 d

28 d

Bottle 1

4

57

63

64

Bottle 2

5

63

74

82

Mean

5

60

69

73

 

 

 

 

 

% degradation in toxicity control

Bottle 1

33

58

76

76

Bottle 2

28

59

77

76

Mean

31

59

77

76

 

 

 

 

 

% degradation of reference substance

Bottle 1

69

77

79

85

Bottle 2

66

75

84

86

Mean

68

76

82

86

The test item is not inhibitory to the inoculum based on the results from the toxicity control.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Readily biodegradable: 73% after 28 d (O2 consumption, EU Method C.4-E: Closed Bottle Test)

Description of key information

Readily biodegradable: 73% after 28 d (O2 consumption, EU Method C.4 -E: Closed Bottle Test)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One experimental study is available investigating the biodegradation of the test item according to EU Method C.4 -E: Closed Bottle Test under GLP conditions (2000). A closed bottle test was performed for this substance due to volatility (vapour pressure: 100 Pa at 20 °C). Secondary effluent from a domestic sewage treatment plant was used as inoculum. 2.9 mg/L of the test item was applied to the test vessels and biodegradation was recorded over a period of 28 d. After 28 d the substance was degraded to 73% based on O2 consumption. In conclusion, the substance is readily biodegradable according to the OECD criteria. A toxicity control containing both, test substance and reference substance, did not indicate any toxic effects of the test item (76% degradation after 28 d).

[Type of water: freshwater]