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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:
2002-03-07 to 2002-06-19
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): activated sludge from a wastewater treatment plant (ARA Ergolz II, Fullinsdorf, Switzerland) treating predominantly domestic wastewater.

- Preparation of inoculum for exposure: washed once with tap water

- Concentration of sludge: 30mg dry material per litre
Duration of test (contact time):
28 d
Initial conc.:
102 mg/L
Based on:
test mat.
Initial conc.:
101 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS

- Test temperature: 22°C

- pH: 7.3-8.1

- pH adjusted: no

- Continuous darkness: yes


TEST SYSTEM

- Culturing apparatus: 500mL Erlenmeyer flasks,

- Number of culture flasks/concentration: two test substance flasks, two inoculum control flasks, two reference substance flasks, one abiotic control flask, one toxicity control flask.

SAMPLING

- Sampling frequency: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 26, 27, 28 days

- Sampling method: Electro-chemical analysis: as dissolved oxygen consumed CO2 is generated. The CO2 is absorbed by soda lime and the total pressure decreases in the airtight flasks. The pressure drop is detected by electrode type manometer. The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulphate solution.

CONTROL AND BLANK SYSTEM

- Inoculum blank: yes

- Abiotic sterile control: yes

- Toxicity control: yes
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
69
Sampling time:
28 d
Details on results:
A biodegradation rate for the test substance of 60% of the ThOD in a 10-day window within the 28-day test period was not reached.

The biodegradation of the reference substance was 82% after 14 days (84% after 28 days). This fulfils the validity criteria of the guideline.

The biodegradation of the toxicity control was 60% after 14 days. This fulfils the validity criteria of the guideline (>25% within 14 days for test substance with no inhibitory effect)

No degradation of the test item occurred in the abiotic control under the test conditions.

Table 1: Cumulative biochemical oxygen demand (BOD mg O2/L) and Percentage Biodegradation

Days

Test Suspension

Inoculum Blank

Reference Control

Toxicity Control

Abiotic Control

BOD (mg O2/L)

% Degradation

BOD (mg O2/L)

BOD (mg O2/L)

% Degradation

BOD (mg O2/L)

% Degradation

BOD (mg O2/L)

R1

R2

R1

R2

R1

R2

R1

R2

R1

R2

R1

R1

R1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

2

2

1

1

1

0

11

9

6

5

6

2

0

2

7

7

3

3

2

1

78

81

46

48

86

25

0

3

17

19

6

7

7

6

95

97

53

54

105

29

1

4

44

44

21

21

7

6

108

107

61

60

135

38

1

5

49

49

24

24

7

6

119

115

67

65

147

41

1

6

52

52

26

26

7

6

124

121

70

69

155

43

1

7

56

56

28

28

7

6

130

127

74

72

171

48

1

8

59

60

29

30

8

7

135

133

76

75

191

54

1

9

61

64

30

32

9

8

138

137

78

77

195

54

1

10

64

70

31

35

10

8

141

141

79

79

199

55

1

11

68

82

33

41

10

9

143

145

80

81

203

57

1

12

-

-

-

-

-

-

-

-

-

-

-

-

-

13

93

102

46

52

12

11

146

147

81

81

211

58

1

14

99

107

49

54

12

11

147

149

81

82

217

60

1

15

106

114

52

57

15

14

150

153

81

83

227

62

1

16

111

118

55

59

15

14

150

153

81

83

235

64

1

17

115

123

57

62

15

14

151

155

82

84

245

67

1

18

-

-

-

-

-

-

-

-

-

-

-

-

-

19

125

133

62

67

16

15

152

157

82

85

259

71

1

20

127

134

63

68

16

15

152

157

82

85

263

72

1

21

129

136

64

68

17

16

152

159

81

85

265

73

1

22

130

138

64

69

18

17

153

159

81

85

269

73

1

23

131

139

64

69

18

17

153

159

81

85

271

74

1

24

132

140

65

70

18

17

153

160

81

85

273

75

1

25

-

-

-

-

-

-

-

-

-

-

-

-

-

26

133

142

65

71

18

17

153

161

81

86

283

78

1

27

133

142

65

71

18

17

153

163

81

87

283

78

1

28

136

145

66

72

20

19

154

165

81

87

287

78

1

Mean (Day 28)

-

69

-

-

84

-

-

-

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
A biodegradation rate of 69% within 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The 10 day window was not met.

Description of key information

Biodegradation in water screening tests: Readily biodegradable but failing the 10-day window. Once the biodegradation of the alkoxy groups is taken into account there is evidence that the methacrylate side-chain is biodegrading to some extent, but it is unlikely that the silanol hydrolysis product would meet the criteria for rapid biodegradability.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window
Type of water:
freshwater

Additional information

Two reliable studies are available. A study conducted according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) gave a result of 69% biodegradation in 28 days (not passing the 10-day window) (Grutzner 2002). This is selected as the key study as it was the study conducted most recently.

A study conducted according to EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test) gave a result of 74% biodegradation in 28 days (not passing the 10-day window) (Enste-Diefenback 1995). This is used as a supporting study.

Based on these two studies it is concluded that the substance is readily biodegradable but failing the 10-day window.

3-Trimethoxysilylpropyl methacrylate hydrolyses within the timescale of the ready biodegradation study (1.87 h at pH 7 and 20ºC to form 3-(trihydroxysilyl)propyl methacrylate and methanol. The biodegradation observed in the study is largely attributable to the biodegradation of the methanol hydrolysis product.

Methanol is readily biodegradable (OECD 2004a). Once the biodegradation of the methanol is taken into account there is evidence that the methacrylate side-chain is biodegrading to some extent, but it is unlikely that the silanol hydrolysis product would meet the criteria for rapid biodegradability. 

Reference:

OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.