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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:
From 18.03.1997 to 16.04.1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to EU Method C.4-C with GLP statement. All validity criteria were fulfilled and no deviations from the protocol were observed.
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): From Municipal activated sludge plant (Marl, East).
- Concentration of sludge: content of suspended solids = 29.7 mg/L. Dry matter content of the inoculum used = about 4.4 g/L.
- Initial cell/biomass concentration: 122.10^4 CFU (colony forming units)/mL
Duration of test (contact time):
29 d
Initial conc.:
ca. 20.7 mg/L
Based on:
test mat.
Initial conc.:
ca. 15 mg/L
Based on:
other: C
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
2 days before testing, 40 L of mineral medium were made and ventilated overnight. For the test, inoculation with inoculum up to 3L with mineral medium.
- Composition of medium: no data
- Additional substrate: no data
- Solubilising agent (type and concentration if used): None
- Test temperature: 20.4 to 23.6°C (mean of 22.1°C)
- pH: 7.5 to 7.6
- pH adjusted: no
- Aeration of dilution water: yes

TEST SYSTEM
- Culturing apparatus: 5 L Glass vessel
- Number of culture flasks/concentration: 1 concentration / 4 vessels
- Method used to create aerobic conditions: no data
- Measuring equipment: TOC analysis

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (2 vessels)
- Abiotic sterile control: no
- Positive control: yes (1 vessel)
Reference substance:
benzoic acid, sodium salt
Preliminary study:
None
Test performance:
None
Key result
Parameter:
% degradation (CO2 evolution)
Value:
75
Sampling time:
29 d
Remarks on result:
other: 10 day window fulfilled
Details on results:
See tables in "Any other information on results incl. tables".
Results with reference substance:
88% biodegradation after 14 and 29 days.

Table 5.2.1/1: Raw data

mg TOC/L 0.05 N NaOH

Days (d)

Control

Mean Control

Reference substance

Test substance

20.6 mg/L

20.7 mg/L

20.8 mg/L

20.6 mg/L

30min.

1

2

3

4

5

9

14

15

20

24

28

29

1.61

3.02

4.00

5.48

7.21

8.24

12.10

15.69

16.35

18.81

20.01

20.70

20.91

1.35

2.79

3.63

4.85

6.60

7.56

11.10

14.58

15.27

18.27

19.68

20.37

20.85

1.48

2.91

3.82

5.17

6.91

7.90

11.60

15.14

15.81

18.54

19.85

20.54

20.88

1.29

12.82

26.07

33.85

37.95

40.95

47.70

53.62

54.67

57.61

58.38

59.01

59.57

1.09

3.28

5.55

8.38

10.57

12.15

17.10

40.20

43.35

50.75

51.45

54.04

53.97

1.11

3.18

5.50

7.56

10.48

12.06

17.97

44.30

46.70

52.75

54.04

55.86

56.35

1.20

3.54

5.50

6.69

10.41

13.11

18.63

40.90

44.00

51.55

52.36

54.18

54.53

1.04

3.65

5.69

7.91

10.70

13.09

18.60

40.75

44.05

51.05

51.66

54.18

54.88

Table 5.2.1/2: Biodegradation of the test and reference substances

Days (d)

Test substance - % biodegradation

Mean % biodegradation of test substance

Reference substance - % biodegradation

20.6 mg/L

20.7 mg/L

20.8 mg/L

20.6 mg/L

30min.

1

2

3

4

5

9

14

15

20

24

28

29

-1

1

4

7

8

9

12

56

61

72

70

74

73

-1

1

4

5

8

9

14

65

69

76

76

78

79

-1

1

4

3

8

12

16

57

62

73

72

74

74

-1

2

4

6

8

12

16

57

63

72

71

75

75

-1

1

4

5

8

11

15

59

64

73

72

75

75

0

23

51

65

71

75

82

88

89

89

88

88

88

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradation of the test substance was 75% after 28 days and the 10 days window was fulfilled. Based on these results, the test substance is considered to be readily biodegradable.
Executive summary:

This study was performed according to modified Sturm test as specified by EC Directive 92/69/EEC C.4 -C with GLP statement, to assess the biodegradation of the test substance for 29 days under aerobic conditions.

The test substance was applied at the rate of c.a 20.7 mg/L of mineral water (without solvent) with activated sludge (4 vessels). To validate the results, two inoculum control vessels (without test substance) and one positive control vessel (reference substance: sodium benzoate with inoculum) were performed. The CO2 evolution was recorded during 29 days (0, 1, 2, 3, 4, 5, 9, 14, 15, 20, 24, 28 and 29 days) by TOC-analysis. The temperature during the test was comprised between 20.4 and 23.6°C with a mean of 22.1°C. The pH was comprised between 7.5 and 7.6.

All validity criteria were fulfilled. The biodegradation of the reference substances was 88% after 14 and 29 days. The biodegradation of the test substance was 75% after 28 days (also after 29 days) and the test substance was degraded by > 60% within 10 days after the time at which the biodegradation has reached 10%.

Based on these results, the test substance is considered to be readily biodegradable.

Description of key information

EU Method C.4-C, GLP, key study, validity 1:

75% biodegradation after 28 days within the 10 day window.

Readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

One valid key study is available to assess the biodegradation potential of the registered substance. This study was performed according to modified Sturm test as specified by EC Directive 92/69/EEC C.4 -C with GLP statement, to assess the readily biodegradation of the registered substance for 29 days under aerobic conditions. The substance attained 75% biodegradation after 28 and 29 days of incubation within the 10 day window.

Therefore, the substance can be considered to be readily biodegradable.