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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From January 13 to February 10, 2012.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
According to OECD Guideline 301F. GLP study.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
- Source of inoculum/activated sludge: Aeration tank of Sewage Treatment Plant "Czajka" Warsaw.
- Storage conditions: The coarse particles were removed by filtration. Such prepared sludge was washed in the medium and was placed in laboratory-scale unit where the aerobic conditions were maintained by means of an intense aeration with compressor and aerators.
- Preparation of inoculum for exposure: The concentrated sludge was suspended in mineral medium to yield a concentration of 3-5 g suspended solids/l and it was aerated until application. After complete re-suspension was achieved, a sample was withdrawn just before use for the determination of the dry weight of the suspended solids.
- Pretreatment: Inocula was pre-conditioned to the experimental conditions. Pre-conditioning consisted of aerating activated sludge in mineral medium for 5 days at the test temperature of 22 ºC.
- Concentration of sludge: 30 mg/dm3.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Details on study design:
TEST CONDITIONS
- Composition of medium:
Mineral medium:
The following stock solutions was prepared, using analytical grade reagents:
(a) Monopotassium dihydrogen orthophosphate, KH2PO4 8,50 g
Dipotassium monohydrogen orthophosphate, K2HPO4 21,75 g
Disodium monohydrogen orthophosphate dihydrate Na2HPO4. 2 H2O 33,40 g
Ammonium chloride, NH4Cl 0,50 g
Dissolve in water and make up to 1 litre The pH of the solution should be 7,4.
(b) Calcium chloride, anhydrous, CaCl2 27,50 g
Dissolve in water and make up to 1 litre
(c) Magnesium sulphate heptahydrate, MgSO4. 7 H2O 22,50 g
Dissolve in water and make up to 1 litre.
(d) Iron (III) chloride hexahydrate, FeC13. 6H2O 0,25 g
The stock solution was dissolved in water and make up to 1 litre. 10 ml of solution (a) was mixed with 800 ml dilution water, added 1 ml of solutions (b) to (d) and was made up to 1 L with dilution water.
- Test temperature: 22 ± 2 ºC.
- pH: 6-8.5
- pH adjusted: yes, the pH was adjusted to 7.54 with 0.1N NaOH.
- Suspended solids concentration: 30 mg/L

TEST SYSTEM
- Culturing apparatus: Closed WTW OxiTop OC 110 respirometer for BOD determination
- Number of culture flasks/concentration: 3 replicates, each containing test item (100 mg/l) and inoculum 30 mg/dm3 SS .
- Measuring equipment: BOD was determined by closed WTW OxiTop OC 110 repirometer. The oxygen uptake from the readings taken at regular and frequent intervals was calculated, using the methods given by the manufacturer of the equipment. The data were read out every 112 min during the 28 day test (40 320 min that is 360 readings) and were recorded and stored in the measuring heads of the sample bottles.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates, each containing only inoculum 30 mg/dm3 SS.
- Procedure control: 3 replicates, each containing reference item (sodium acetate 100 mg/L) and inoculum 30 mg/dm3 SS.
- Toxicity control: 3 replicates, each containing test item (100 mg/L), reference item (sodium acetate 100 mg/L) and inoculum 30 mg/dm3 SS.
Reference substance:
acetic acid, sodium salt
Remarks:
(100 mg/L)
Key result
Parameter:
% degradation (O2 consumption)
Value:
79.5
Sampling time:
28 d
Details on results:
The aerobic biodegradation of test item methyltriacetoxysilane at 28th day of incubation attained 79.5% of biodegradability. After l0-day window period the degradation reached 77.6%.
Results with reference substance:
The aerobic biodegradation of reference item sodium acetate at 28th day of incubation reached 81.6% of biodegradability.

At 28th day of the aerobic biodegradation test, in the toxicity test the biodegradation was equal to 83.9%.

The oxygen uptake of the inoculum blank was equal to 43.4 mg/dm3 in 28 days.

The recorded temperature didn’t exceed - by 0.4 ºC - the expected 22 ºC.

The pH values of all flasks were inside the range 6-8.5.

Table: Sample oxygen uptake: Biodegradability:

 

time, days

3

5

7

9

12

14

16

18

21

23

25

28

Test item O2uptake, mg/dm3

a1

72.4

89.6

101.5

107.5

114.0

117.2

118.0

119.0

121.5

124.7

127.2

129.6

a2

68.1

83.3

92.3

98.9

106.1

111.3

113.6

114.8

117.0

119.2

121.5

123.7

a3

65.6

81.6

91.7

98.5

107.0

110.1

112.9

114.0

115.3

118.8

121.6

123.5

am. avg

68.7

84.8

95.1

101.6

109.0

112.9

114.8

115.9

117.9

120.9

123.4

125.6

Blank test O2uptake. mg/dm3

b1

8.7

13.8

17.5

20.2

28.6

32.1

37.0

39.8

42.5

42.2

44.7

45.8

b2

5.0

9.3

11.4

14.5

21.6

30.9

31.2

33.3

34.9

35.2

37.2

38.8

b3

8.4

12.2

13.4

16.9

27.7

34.2

36.2

39.7

42.8

42.5

43.2

45.5

bm. avg

7.4

11.8

14.1

17.2

26.0

32.4

34.8

37.6

40.0

40.0

41.7

43.4

Referencet item O2uptake. mg/dm3

w1

53.1

67.0

74.7

79.8

87.6

90.5

93.3

96.3

100.9

101.0

104.0

106.7

w2

59.7

71.0

79.6

85.5

91.8

95.2

97.1

98.5

101.0

101.0

103.7

104.0

w3

59.8

75.6

83.0

89.4

95.9

98.3

100.8

101.0

104.0

105.6

107.0

110.5

wm. avg

57.5

71.2

79.1

84.9

91.8

94.6

97.1

98.6

102.0

102.5

104.9

107.0

Toxicity control O2uptake. mg/dm3

tox1

110.6

132.1

143.5

152.0

162.2

167.6

170.8

175.9

180.6

186.4

189.8

195.4

tox2

131.8

155.0

166.0

172.6

179.0

182.4

185.7

189.3

191.8

195.3

198.0

202.7

tox3

116.8

139.1

154.4

163.7

172.0

174.0

177.0

180.6

183.0

185.0

186.0

188.7

toxm. avg

119.7

142.1

154.7

162.8

171.1

174.7

177.9

181.9

185.2

188.9

191.3

195.6

 

Corrected

BOD. mg/dm3

(a1-bm)

65.0

77.8

87.4

90.3

88.1

84.8

83.2

81.4

81.4

84.8

85.5

86.2

(a2-bm)

60.7

71.6

78.2

81.7

80.1

78.9

78.8

77.2

76.9

79.3

79.8

80.3

(a3-bm)

58.3

69.8

77.6

81.3

81.0

77.7

78.1

76.4

75.3

78.8

79.9

80.1

test item

% degradation

ThOD = 103.4

mgO2/l

R1(a1)

62.9

75.3

84.5

87.3

85.2

82.1

80.4

78.7

78.7

82.0

82.7

83.4

R2(a2)

58.7

69.2

75.6

79.1

77.5

76.3

76.3

74.6

74.4

76.7

77.2

77.7

R3(a3)

56.3

67.5

75.1

78.6

78.4

75.2

75.5

73.9

72.8

76.2

77.3

77.5

R. avg

59.3

70.7

78.4

81.7

80.3

77.8

77.4

75.7

75.3

78.3

79.0

79.5

reference item

% degradation

ThOD = 78.0

mgO2/l

R1(tox1)

58.6

70.8

77.7

80.3

79.0

74.5

75.0

75.3

78.0

78.3

79.9

81.1

R2(tox2)

67.1

75.9

84.0

87.6

84.5

80.5

79.9

78.1

78.1

78.3

79.5

77.7

R3(tox3)

67.2

81.8

88.4

92.5

89.7

84.5

84.6

81.3

82.0

84.2

83.8

86.0

Rtoxavg

64.3

76.2

83.3

86.8

84.4

79.8

79.8

78.2

79.4

80.2

81.0

81.6

toxicity control

% degradation

ThOD = 181.4

mgO2/l

R1(tox1)

56.9

66.3

71.4

74.3

75.1

74.6

75.0

76.2

77.5

80.7

81.6

83.8

R2(tox2)

68.6

79.0

83.8

85.7

84.4

82.7

83.2

83.6

83.7

85.6

86.2

87.8

R3(tox3)

60.3

70.2

77.4

80.8

80.5

78.1

78.4

78.9

78.8

80.0

79.6

80.1

Rtoxavg

61.9

71.8

77.5

80.3

80.0

78.4

78.9

79.6

80.0

82.1

82.5

83.9

Validity criteria fulfilled:
yes
Remarks:
(difference of extremes of replicate values of the removal of the test item at the end of test < 20%; the reference item has reached the pass level on day 2.3; in the toxicity test the biodegradation was 78.4% within 14 days; pH was inside 6-8.5)
Interpretation of results:
readily biodegradable
Conclusions:
The aerobic biodegradation of test item methyltriacetoxysilane (100 mg/L) after 28 days of incubation with activated sludge (33 mg/L SS), attained 79.5% of biodegradation, based on O2 consumptiom.
Executive summary:

The study of readily biodegradability of test item methyltriacetoxysilane in an aerobic aqueous medium with manometric respirometry method was carried out according to OECD Guideline 301 F. 100 mg/l of test item was inoculated with adapted activated sludge (30 mg/L SS) and incubated under aerobic conditions (oxygen presence) in a closed respirometer flask at constant temperature (± 2) for 28 days. The blank test, the procedure test with reference substance (sodium acetate) and the toxicity tests were run in parallel.

The consumption of oxygen was determined from the change in pressure in the apparatus (readings every 112 min during the 28 days). The carbon dioxide, evolved during test item degradation, was absorbed in a solution of potassium hydroxide. The amount of oxygen taken up by the test item (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of calculated ThOD (Theoretical Oxygen Demand) from known molecular formula.

At the 28th day of the test, the aerobic biodegradation of test item methyltriacetoxysilane attained 79.5% of biodegradability (after 10 -day window period the degradation reached 77.6%) and therefore the substance was determined to be readily biodegradable under aerobic aqueous conditions. Furthermore, the reference item reached 81.6% of biodegradability (operation of the procedure correct) and in the toxicity test the biodegradation was equal to 83.9% (no inhibitory effect of the test item). The validity criteria were fulfilled.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Test method according to OECD 301C.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Concentration of sludge: 30 mg/L
Duration of test (contact time):
2 wk
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Parameter followed for biodegradation estimation:
test mat. analysis
Reference substance:
not specified
Parameter:
% degradation (O2 consumption)
Remarks:
(BOD)
Value:
74
Sampling time:
2 wk
Parameter:
% degradation (test mat. analysis)
Value:
100
Sampling time:
2 wk
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Acetic acid reached 74% of its theoretical BOD in 2 weeks using the Japanese MITI test.
Executive summary:

Acetic acid, present at 100 mg/L, reached 74% of its theoretical BOD in 2 weeks using an activated sludge inoculum at 30 mg/L and the Japanese MITI test.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
Test method similar to OECD guideline 302 B. No GLP.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Deviations:
not specified
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, industrial (adaptation not specified)
Duration of test (contact time):
3 d
Initial conc.:
1 000 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Reference substance:
diethylene glycol
Remarks:
(0.5 g/L)
Parameter:
% degradation (DOC removal)
Value:
> 90
Sampling time:
3 d
Results with reference substance:
Degradation of 90 % in 9 days.

Acetic acid was inherently biodegradable.

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
Acetic acid was inherently biodegradable.
Executive summary:

Acetic acid was found to degrade > 90 % after 3 days in a Zahn-Wellens test using an activated sludge inocula.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
The analogue Methyltriacetoxysilane which shares the same functional group with Triacetoxyvinylsilane, also has comparable values for the relevant molecular properties for biodegradation.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 79.5
Sampling time:
28 d
Remarks on result:
other: (% degradation of analogue substance methyltriacetoxysilane)
Details on results:
Based on the experimental results obtained with the analogue substance methyltriacetoxysilane (100 mg/L) which was found to degrade up to 79.5 % after 28 days incubation with activate sludge inoculum (30 mg/L SS), the read-across was applied and Triacetoxyvinylsilane was also considered to be readily biodegradable under test conditions.
After l0-day window period the degradation of analogue substance methyltriacetoxysilane reached 77.6%.
Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Conclusions:
Based on read-across approach from experimental data on analogue substance Methyltriacetoxysilane, Triacetoxyvinylsilane is determined to be readily biodegradable.
Executive summary:

Based on experimental results on analogue substance Methyltriacetoxysilane (100 mg/L) where 79.5% of biodegradation was reached after 28 days of incubation with activated sludge inoculum (30 mg/L SS) in aerobic conditions in a manometric respirometry test (OECD Guideline 301F), the read-across approach was applied and Triacetoxyvinylsilane is determined to be readily biodegradable under aerobic aqueous conditions. Furthermore, it is assumed that Triacetoxyvinylsilane is not inhibitory to activated sludge in an estimated concentration of 105.45 mg/L based on the experimental results with the analogue substance were 83.9% of biodegradation was obtained in the toxicity test after 28 days of incubation.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Triacetoxyvinylsilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the relevant molecular properties for biodegradation in water are due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (O2 consumption)
Value:
74
Sampling time:
2 wk
Remarks on result:
other: (% degradation of the analogue substance, acetic acid)
Parameter:
% degradation (test mat. analysis)
Value:
100
Sampling time:
2 wk
Remarks on result:
other: (% degradation of the analogue substance, acetic acid)
Details on results:
Based on the experimental results obtained with the supporting substance Acetic acid (reached 74% of its theoretical BOD in 2 weeks using the Japanese MITI test), and applying the read-across approach, the substance triacetoxyvinylsilane is also considered to be readily biodegradable under test conditions.
Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid (reached 74% of its theoretical BOD in 2 weeks using the Japanese MITI test), and applying the read-across approach, the substance triacetoxyvinylsilane is also considered to be readily biodegradable under test conditions.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid (reached 74% of its theoretical BOD in 2 weeks using the Japanese MITI test), and applying the read-across approach, the substance triacetoxyvinylsilane is also considered to be readily biodegradable under test conditions.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Triacetoxyvinylsilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the relevant molecular properties for biodegradation in water are due to the acetic acid and their values are comparable.
See attached the reporting format.
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (DOC removal)
Value:
> 90
Sampling time:
3 d
Remarks on result:
other: (% degradation of the analogue substance, acetic acid)
Details on results:
Based on the experimental results obtained with the supporting substance acetic acid which was found to degrade > 90 % after 3 days in a Zahn-Wellens test using an activated sludge inocula), and applying read across approach, triacetoxyvinylsilane is considered to be biodegradable under test conditions.
Validity criteria fulfilled:
not applicable
Interpretation of results:
inherently biodegradable
Conclusions:
Based on the experimental results obtained with the supporting substance acetic acid which was found to degrade > 90 % after 3 days in a Zahn-Wellens test using an activated sludge inocula), and applying read across approach, triacetoxyvinylsilane is considered to be biodegradable under test conditions.
Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid which was found to degrade > 90 % after 3 days in a Zahn-Wellens test using an activated sludge inocula), and applying read across approach, triacetoxyvinylsilane is considered to be biodegradable under test conditions.

Description of key information

Key study: Based on read-across approach from experimental data on analogue Methyltriacetoxysilane (OECD 301F, GLP study), Triacetoxyvinylsilane is determined to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Key study: Read-across from analgoue substance Methyltriacetoxysilane:

In the readily biodegradability study conducted on analogue Methyltriacetoxysilane according to OECD 301F (GLP study), 79.5% of biodegradation was obtained after 28 days of incubation with activated sludge inoculum in aerobic conditions. Based on these results, the read-across was applied and Triacetoxyvinylsilane is determined to be readily biodegradable under aerobic aqueous conditions.

Supporting studies: Read-across from hydrolsysis product acetic acid.

In the readily biodegradation study performed by the Institute of Technology and Evolution (1993) according to OECD 301C (Japanese MITI test) on supporting substance acetic acid, which reached the 74% of its theoretical BOD in 2 weeks, the read-across approach was applied and the substance Triacetoxyvinylsilane was considered to be readily biodegradable under test conditions.

In the study by Zahn and Wellen, 1980, performed with a method similar to OECD 302B, acetic acid was found to degrade > 90% after 3 days. Based on this experimental result on the supporting substance acetic acid, the read-across approach was applied and Triacetoxyvinylsilane was considered to be biodegradable under test conditions.