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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:
08 Mar 2004 to 08 Apr 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
1993
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Version / remarks:
1992
Qualifier:
according to
Guideline:
other: ISO 9439:1999 (Water Quality - Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds - Method by analysis of released carbon dioxide)
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Specific details on test material used for the study:
- Appearance: White, powdered solid
- Water-solubility: <10 mg/L
- Homogeneity: homogeneous
- Storage conditions: at room temperature
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge from laboratory wastewater plant treating municipal sewage.
Duration of test (contact time):
28 d
Initial conc.:
32.7 mg/L
Based on:
test mat.
Initial conc.:
20 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Test temperature: 22 ± 2 °C
- Preparation inoculum: Activated sludge was pre-aerated for about two days before the start of the test.
- Sludge concentration in the test vessel: 30 mg/L Dw

TEST SYSTEM
- Number of culture flasks/concentration: 2 for the control, 2 for the test substance (1 concentration), 1 for the reference substance and one for the inhibition control
- Test volume: 1500 mL
- Method test substance addition: direct addition

MEASUREMENT AND CALCULATION
- The produced CO2 was trapped in a absorption solution (0.25 mol. potassium hydroxide). The conductivity shift of the solution was daily recorded and used for calculation of the biodegradation for each day.
Reference substance:
aniline
Test performance:
VALIDITY CRITERIA
- Deviation of the degradation degree of the test subst. in the plateau phase was <20%
- Degradation degree of the reference substance was >60% after 14 days (see 'Results with reference substance')
- Degradation degree in the inhibition control was >25 % after 14 days
- DOC in the blank control by test begin at 20 mg/l TOC test concentration was <1 mg/L
- CO2-production in the blank control was <70 mg/L
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 80 - <= 90
Sampling time:
28 d
Details on results:
The duration of the adaptation phase was 4 days. The test substance was biodegraded for 60-70% at the end of the 10-day window. After 28 days, the biodegradation degree had increased to 80-90%. For more detail, see 'Any other information on results incl. tables'.
The degree of biodegradation in the inhibition control after 14 days was 60-70%.
Results with reference substance:
Biodegradation degree of the reference substance after 14 days was 60-70% C02/ThCO2

PRODUCED CARBON DIOXIDE AMOUNT IN THE TEST VESSELS:

 

Table: conductivity measurements and produced carbon dioxide amount in the test vessels

Duration of exposure [days]

Conductivity: measured values by daily reading [mS/cm]

SCO2: summarized CO2-production [mg/test vessel]

BC1

BC2

RS

IH

TS1

TS2

RS

SCO2

IH

SCO2

TS1

SCO2

TS2

SCO2

0

51.6

52.3

53.2

52.9

51.7

51.8

0.0

0.0

0.0

0.0

1

51.2

52.1

52.9

52.6

51.4

51.6

2.6

2.6

2.6

1.9

2

50.7

51.8

52.6

52.1

50.9

51.3

1.9

3.4

3.4

1.1

3

50.2

51.5

52.2

51.7

50.4

50.9

1.9

3.4

4.1

1.1

4

49.9

50.9

51.0

48.9

49.2

50.0

7.2

20.9

9.5

4.1

5

49.6

50.5

48.6

44.1

46.8

48.3

23.2

55.1

25.4

14.8

6

49.3

50.1

47.2

41.3

45.1

46.8

30.8

73.4

35.3

23.2

7

48.9

49.7

46.0

38.9

43.7

45.0

36.9

88.6

43.0

33.8

8

48.2

49.0

44.8

36.8

42.3

43.3

40.7

99.3

48.3

41.4

9

48.1

48.9

44.3

35.4

41.7

42.5

43.7

109.2

52.1

46.8

10

48.0

48.7

43.6

34.1

40.9

41.7

48.3

118.3

57.4

52.1

11

47.8

48.5

43.0

32.9

40.3

40.9

51.3

125.9

60.5

56.6

12

47.5

48.3

42.2

31.9

39.7

40.3

55.1

131.2

62.7

58.9

13

47.3

48.1

40.9

30.7

39.1

39.7

63.5

138.8

65.8

62.0

14

47.0

47.8

40.1

29.3

38.4

38.8

67.3

147.2

68.8

66.5

15

46.8

47.7

39.8

28.6

37.7

38.2

68.8

151.8

73.4

70.3

16

46.6

47.5

39.5

27.7

36.9

37.4

69.6

157.1

78.0

74.9

17

46.4

47.4

39.0

27.0

36.3

36.7

71.9

160.9

81.0

78.7

18

46.2

47.2

38.5

26.4

35.8

36.1

74.2

163.9

83.3

81.8

19

45.9

47.0

38.1

25.7

35.2

35.6

75.7

167.7

86.3

84.0

20

45.8

46.8

37.7

25.2

34.8

35.2

77.2

170.0

87.8

85.6

21

45.6

46.7

37.4

24.8

34.5

34.8

78.7

172.3

89.4

87.8

22

45.4

46.5

37.1

24.4

34.3

34.5

79.5

173.8

89.4

88.6

23

45.2

46.4

36.8

23.9

34.0

34.2

80.2

176.1

90.1

89.4

24

45.1

46.2

36.5

23.5

33.7

34.0

81.8

178.4

91.7

90.1

25

44.9

46.0

36.2

23.1

33.5

33.7

82.5

179.9

91.7

90.9

26

44.7

45.9

35.9

22.7

33.3

33.4

83.3

181.4

91.7

91.7

27

44.6

45.7

35.6

22.5

33.1

33.2

84.8

182.2

92.4

92.4

28

44.4

45.6

35.3

22.3

32.9

33.0

87.8

182.2

93.2

93.2

29

43.9

45.2

34.6

21.9

32.4

32.5

 

 

 

 

BC = blank control; RS = reference substance; IH = inhibition control; TS = test substance

- Remark: The measured values of day 29 are influenced by CO2stripping and therefore added to the values of day 28. Correlation tor calculation from the conductivity change to the produced CO2 amount in the test vessels y=7,6097x+2,61 91.

 

 

CALCULATION OF DEGREE BIODEGRADATION:

 

Table: theoretical carbon dioxide [mg/test vessel]

RS: 110.0

IH: 220.2

TS1: 110.4

TS2: 110.4

 

BC = blank control; RS = reference substance; IH = inhibition control; TS = test substance

 

 

Table: degree of biodegradation; [CO2/ThCO2]

Test duration [days]

RS

IH

TS1

TS2

TS mv

0

0

0

0

0

0

1

2

1

2

2

2

2

2

2

3

1

2

3

2

2

4

1

3

4

7

9

9

4

7

5

21

25

23

13

18

6

28

33

32

21

27

7

34

40

39

31

35

8

37

45

44

38

41

9

40

50

47

42

45

10

44

54

52

47

50

11

47

57

55

51

53

12

50

60

57

53

55

13

58

63

60

56

58

14

61

67

62

60

61

15

63

69

66

64

65

16

63

71

71

68

70

17

65

73

73

71

72

18

67

74

75

74

75

19

69

76

78

76

77

20

70

77

80

78

79

21

72

78

81

80

81

22

72

79

81

80

81

23

73

80

82

81

82

24

74

81

83

82

83

25

75

82

83

82

83

26

76

82

83

83

83

27

77

83

84

84

84

28

80

83

84

84

84

BC = blank control; RS = reference substance; IH = inhibition control; TS = test substance; mv = mean value

 

MEASUREMENT OF DISSOLVED ORGANIC CARBON:

 

Table: measured values [mg/L], DOC - elimination degree [%]

 

[mg/L DOC]

BC1

BC2

BC mv

RS

IH

TS1

TS2

TS mv

DOC at test begin

0.3

0.6

 

0.5

19.4

-

-

-

 

0.5

0.7

19.5

-

-

-

DOC at test end

0.6

1.1

 

0.9

2.3

-

-

-

0.6

1.3

2.2

-

-

-

DOC elimination [%]

93

-

-

-

-

BC = blank control; RS = reference substance; IH = inhibition control; TS = test substance; mv = mean value

- Remark: The test substance is poorly soluble in water, therefore no DOC elimination was determined

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance is readily biodegradable (according to OECD criteria).

Description of key information

The test substance was found to be readily biodegradable in an OECD 301B guideline study.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation potential of the substance in water was determined in a screening study according to OECD TG 301B (CO2-Evolution Test) and in compliance with GLP criteria. In this study, 32.7 mg/L test substance (corresponding to 20 mg/L TOC) was inoculated with activated sludge from predominantly domestic sewage for 28 days under aerobic conditions. Throughout the incubation period the evolved CO2 was determined and compared to the ThCO2 as indication of biodegradation. Based on CO2/ThCO2, 80 - 90% of the test substance was biodegraded after the 28-day exposure period. Degradation of the test substance at the end of the 10-day window was 60-70% CO2/ThCO2; the10-day window criterion was met. Based on these findings the substance is classified as readily biodegradable.