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Environmental fate & pathways

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:
2018-19-04 to 2018-14-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
A fresh sample of activated sludge was collected from a sewage treatment plant as recommended by the Guidelines for the Testing of Chemicals, MEP, P.R. China and the OECD Guidelines for the Testing of Chemicals. A fresh sample of activated sludge was collected from the aeration tank of Shenyang North Sewage Treatment Plant 1 day before the test exposure was started. It is a well-functioning treatment plant receiving predominantly domestic sewage.
Duration of test (contact time):
28 d
Initial conc.:
20.69 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
See "any other information on materials and methods incl. tables".
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
14.8
Sampling time:
28 d
Details on results:
See "any other information on results incl. tables".
Parameter:
BOD5
Value:
0.386 g O2/g test mat.
Parameter:
ThOD
Value:
2.61 g O2/g test mat.
Results with reference substance:
See "any other information on results incl. tables".

Table 1. Biodegradation Results of Test Item (28 days)

Day

O2–uptake

(mg O2/L)

BOD

(mgO2/mg test item)

Biodegradation

(%)

IC-1

IC-2

TS-1

TS-2

IC Average

TS-1

TS-2

TS

Average

TS-1

TS-2

TS

Average

1

1.77

2.25

1.37

1.62

2.01

0.000

0.000

0.000

0.0

0.0

0.0

2

8.21

9.12

6.60

6.85

8.67

0.000

0.000

0.000

0.0

0.0

0.0

3

13.43

13.79

11.70

12.00

13.61

0.000

0.000

0.000

0.0

0.0

0.0

4

16.22

16.45

15.20

15.72

16.34

0.000

0.000

0.000

0.0

0.0

0.0

5

18.39

18.64

17.51

18.14

18.52

0.000

0.000

0.000

0.0

0.0

0.0

6

20.20

20.43

19.64

20.28

20.32

0.000

0.000

0.000

0.0

0.0

0.0

7

21.55

21.68

21.70

22.20

21.62

0.004

0.028

0.016

0.2

1.1

0.7

8

22.64

22.80

24.05

24.24

22.72

0.065

0.073

0.069

2.5

2.8

2.7

9

23.53

23.80

26.32

26.24

23.67

0.129

0.123

0.126

4.9

4.7

4.8

10

24.24

24.55

28.24

27.93

24.40

0.187

0.169

0.178

7.2

6.5

6.9

11

24.82

25.18

29.84

29.47

25.00

0.236

0.214

0.225

9.0

8.2

8.6

12

25.39

25.78

31.15

31.01

25.59

0.271

0.260

0.266

10.4

10.0

10.2

13

25.43

26.01

31.61

32.03

25.72

0.287

0.302

0.295

11.0

11.6

11.3

14

25.64

26.45

32.13

32.95

26.05

0.296

0.331

0.314

11.3

12.7

12.0

15

26.22

27.22

33.05

34.01

26.72

0.309

0.349

0.329

11.8

13.4

12.6

16

26.64

27.80

33.72

34.74

27.22

0.317

0.360

0.339

12.1

13.8

13.0

17

26.89

28.24

34.13

35.19

27.57

0.320

0.365

0.343

12.3

14.0

13.2

18

26.91

28.55

34.22

35.38

27.73

0.316

0.367

0.342

12.1

14.1

13.1

19

27.61

29.28

35.07

36.24

28.45

0.323

0.373

0.348

12.4

14.3

13.4

20

27.84

29.80

35.55

36.65

28.82

0.328

0.375

0.352

12.6

14.4

13.5

21

28.86

30.65

36.55

37.84

29.76

0.331

0.387

0.359

12.7

14.8

13.8

22

28.86

30.95

36.94

38.13

29.91

0.343

0.394

0.369

13.1

15.1

14.1

23

28.86

31.47

37.36

38.61

30.17

0.351

0.404

0.378

13.4

15.5

14.5

24

28.86

31.86

37.67

39.01

30.36

0.356

0.414

0.385

13.6

15.9

14.8

25

28.91

32.09

37.73

39.05

30.50

0.353

0.410

0.382

13.5

15.7

14.6

26

28.91

32.59

38.03

39.40

30.75

0.355

0.414

0.385

13.6

15.9

14.8

27

28.91

32.97

38.23

39.59

30.94

0.355

0.414

0.385

13.6

15.9

14.8

28

28.91

33.26

38.34

39.82

31.09

0.353

0.418

0.386

13.5

16.0

14.8

Note: IC =InoculaControl; TS = Test Suspension.

Table 2. Biodegradation Results of ASC, Toxicity Control and Reference Item

(28 days)

Day

O2–uptake

(mg O2/L)

BOD

(mgO2/mg test item)

Degradation

(%)

Biodegradation

(%)

ASC

IC-1

IC-2

TC

PC

IC

Average

ASC

PC

ASC

TC

PC

1

0.00

1.77

2.25

29.13

26.97

2.01

0.000

0.799

0.0

25.4

47.8

2

0.00

8.21

9.12

38.28

35.51

8.67

0.000

0.859

0.0

27.7

51.4

3

0.00

13.43

13.79

44.77

43.79

13.61

0.000

0.966

0.0

29.1

57.8

4

0.00

16.22

16.45

53.77

51.40

16.34

0.000

1.123

0.0

35.0

67.2

5

0.00

18.39

18.64

60.75

57.46

18.52

0.000

1.247

0.0

39.5

74.7

6

0.00

20.20

20.43

66.04

61.93

20.32

0.000

1.332

0.0

42.8

79.8

7

0.00

21.55

21.68

70.08

64.89

21.62

0.000

1.386

0.0

45.3

83.0

8

0.00

22.64

22.80

73.30

67.08

22.72

0.000

1.420

0.0

47.3

85.0

9

0.00

23.53

23.80

75.64

69.01

23.67

0.000

1.452

0.0

48.6

86.9

10

0.00

24.24

24.55

77.55

70.60

24.40

0.000

1.479

0.0

49.7

88.6

11

0.00

24.82

25.18

79.09

71.87

25.00

0.000

1.501

0.0

50.6

89.9

12

0.33

25.39

25.78

80.41

72.97

25.59

0.016

1.517

0.6

51.3

90.8

13

0.33

25.43

26.01

81.20

73.41

25.72

0.016

1.527

0.6

51.9

91.4

14

0.33

25.64

26.45

82.22

73.99

26.05

0.016

1.535

0.6

52.5

91.9

15

0.79

26.22

27.22

83.22

74.89

26.72

0.039

1.542

1.5

52.8

92.3

16

1.29

26.64

27.80

83.97

75.57

27.22

0.064

1.548

2.5

53.1

92.7

17

1.71

26.89

28.24

84.55

76.03

27.57

0.085

1.552

3.3

53.3

92.9

18

1.77

26.91

28.55

84.76

76.18

27.73

0.088

1.551

3.4

53.3

92.9

19

2.50

27.61

29.28

85.65

76.97

28.45

0.125

1.554

4.8

53.5

93.1

20

2.81

27.84

29.80

86.26

77.41

28.82

0.140

1.556

5.4

53.7

93.2

21

4.12

28.86

30.65

87.38

78.51

29.76

0.206

1.561

7.9

53.9

93.5

22

4.12

28.86

30.95

87.88

78.64

29.91

0.206

1.560

7.9

54.2

93.4

23

4.50

28.86

31.47

88.42

79.05

30.17

0.225

1.565

8.6

54.5

93.7

24

4.87

28.86

31.86

88.86

79.41

30.36

0.243

1.571

9.3

54.7

94.1

25

4.91

28.91

32.09

88.90

79.41

30.50

0.245

1.566

9.4

54.6

93.8

26

5.35

28.91

32.59

89.15

79.63

30.75

0.267

1.565

10.2

54.6

93.7

27

5.58

28.91

32.97

89.38

79.86

30.94

0.279

1.566

10.7

54.7

93.8

28

5.77

28.91

33.26

89.57

79.86

31.09

0.288

1.562

11.0

54.7

93.5

Note: ASC=Abiotic Sterile Control; IC =InoculaControl; TC=Toxicity Control;PC =Procedure Control.

The percentage biodegradation of TC was based on total ThOD, BOD (mgO2/mg test item) was not calculated.

Results

The biodegradation of test item after 28 days averaged 14.8% (2 replicates). The test itemdid notexhibit a percentage biodegradation exceeding the pass level of 60% within the 28-day period.

The biodegradation of the reference substance (Sodium benzoate) attained 67.2% after Day 4, 91.9% after Day 14 and 93.5% after Day 28.

In the Toxicity Control (TC) test mixture, 52.5% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. 

In theAbiotic Sterile Control (ASC) Test Vessel, 11.0% degradation occurred after 28 days.

The results are presented in Table 1 and Table 2.

Validity of the Test

The following validity criteria were met by this test:

1)     The oxygen uptake of the inoculum blank was 31.09 mg O2/L in 28 days, which did not exceed 60 mg O2/L.

2)     The pH values were in the range of 7.35 – 7.69, which were in the range of 6-8.5.

3)     The difference of extremes of replicate values of the removal of the test item at the end of the test was 2.5%, it was less than 20%, which is specified criterion in test guideline.

4)     The percentage degradation of the reference item reached 67.2% after day 4, and was 91.9% after day 14 which exceeded the required pass level (the percentage degradation of reference item after day 14³60%).

5)     In Toxicity Control (TC) test mixture, containing both test item and reference item, 25.4% ThOD degradation occurred within 1 days and 52.5% ThOD within 14 daysbased on total ThOD. Since thesevalues exceeded the 25%ThOD limit for toxicity control, it was concluded that the test item is not inhibitory to sludge micro-organisms.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Conclusions
Based on the results, the percentage biodegradation within 28 days did not exceed pass level of 60% ThOD. The test item did not meet the criteria for “ready biodegradability” under the described test conditions.

Executive summary:

The ready biodegradability test ofthe test substancewas conductedwith unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28-day test period.

The test item was added directlyto test vesselsat a level of20.69 mg/L(equivalent to54.00mg/L as Theoretical Oxygen Demand or “ThODNH3”)(average, 2 replicate).The test concentration of sodium benzoate, used as reference substance in the Procedure Control, was31.23 mg/L(equivalent to52.15mg/L as ThOD).In the Toxicity Control (TC) containing both test item and reference substance, the test item wasadded to the test vesselat a level of20.49 mg/L(equivalent to53.48mg/L as ThODNH3)and the reference substance was added at a level of32.00 mg/L ofsodium benzoate(equivalent to53.44mg/L as ThOD), the concentration expressed as totalThODwas 106.92 mg/L. In theAbiotic Sterile Control (ASC) Test Vesselwithout inocula addition andcontainingsterilising agent,the test item wasadded to the test vesselat a level of20.03 mg/L(equivalent to52.28mg/L as ThODNH3).

The biodegradation of test item after 28 days averaged 14.8% (2 replicates). The test itemdid notexhibit a percentage biodegradation exceeding the pass level of 60% within the 28-day period.

The biodegradation of the reference substance (Sodium benzoate) attained 67.2% after Day 4, 91.9% after Day 14 and 93.5% after Day 28.

In the Toxicity Control (TC) test mixture, 52.5% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. 

In theAbiotic Sterile Control (ASC) Test Vessel, 11.0% degradation occurred after 28 days.

Based on the results, the percentage biodegradation within 28 days did notexceedthe pass level of60% ThOD. The test itemdid notmeet the criteria for “ready biodegradability” under the described test conditions. 
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2018-02-23 to 2018-
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
The inoculum was obtained on 27 February 2018 from the activated sludge of the biological wastewater treatment plant from Mourenx (France, 64) which handles predominantly domestic sewage.

On arrival at the laboratory, the sludge (around 1 L) was centrifuged at room temperature for 20 min at 1000 g; the solid sewage inoculant portion was re-suspended in dilution water in order to keep the concentration unchanged with respect to the sample. The inoculum was preconditioned 48 hours (aeration) until the flasks were inoculated.

Sub-samples of the homogenised sludge were dried in an oven at approximately 105°C and the suspended solids content determined to be 2.37 g/L.

The inoculum was not adapted to the test item before the biodegradation test.
Duration of test (contact time):
56 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
See "any other information on materials and methods incl. tables".
Reference substance:
benzoic acid, sodium salt
Test performance:
See "any other information on results incl. tables".
Key result
Parameter:
% degradation (O2 consumption)
Value:
11.8
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
11.1
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
9.2
Sampling time:
56 d
Details on results:
See "any other information on results incl. tables".
Parameter:
ThOD
Value:
2.408 g O2/g test mat.
Results with reference substance:
See "any other information on results incl. tables".

Results and discussion

Table1 Cumulated Biological Oxygen Demand (mg/L)

Day

Fb1

Fb2

Average Fb

Fa1

Fa2

Average Fa

Fc1

Fc2

Average Fc

Ft1

Ft2

Average Ft

Fi

0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

1

0.0

0.0

0.0

0.0

0.0

0.0

47.8

47.8

47.8

0.0

0.0

0.0

61.2

2

0.0

0.0

0.0

0.0

0.0

0.0

80.3

81.7

81.0

0.0

0.0

0.0

79.5

3

0.0

0.0

0.0

0.0

0.0

0.0

96.7

97.7

97.2

0.0

2.7

1.4

110.0

4

0.0

0.0

0.0

0.0

0.0

0.0

121.7

122.6

122.2

3.3

5.0

4.2

137.1

5

0.0

0.0

0.0

0.0

0.0

0.0

128.4

129.3

128.9

6.0

8.6

7.3

147.5

6

0.7

0.0

0.4

0.0

1.4

0.7

135.0

135.9

135.5

9.3

12.0

10.7

159.5

7

1.6

1.3

1.5

0.0

2.4

1.2

139.9

141.3

140.6

12.1

15.5

13.8

164.6

8

2.6

2.9

2.8

0.0

3.7

1.9

144.2

145.8

145.0

14.7

19.0

16.9

167.4

9

3.4

3.4

3.4

0.0

5.3

2.7

147.7

149.4

148.6

17.5

23.4

20.5

170.0

10

4.3

4.8

4.6

0.0

6.9

3.5

150.5

151.9

151.2

20.4

26.7

23.6

172.6

11

5.4

6.1

5.8

0.0

8.8

4.4

153.4

154.8

154.1

23.8

30.2

27.0

175.1

12

5.9

6.1

6.0

0.0

9.7

4.9

155.9

156.8

156.4

26.7

32.3

29.5

176.9

13

6.8

7.3

7.1

0.8

11.2

6.0

158.3

159.4

158.9

29.9

33.3

31.6

179.6

14

7.7

8.6

8.2

1.7

12.5

7.1

161.0

161.9

161.5

33.0

34.6

33.8

182.1

15

8.6

9.2

8.9

2.5

14.2

8.4

163.1

163.8

163.5

34.9

36.9

35.9

184.4

16

9.2

9.7

9.5

3.1

15.2

9.2

165.7

165.9

165.8

37.0

38.1

37.6

186.8

17

9.7

10.3

10.0

3.6

16.5

10.1

167.7

167.6

167.7

38.9

39.3

39.1

189.3

18

11.0

11.5

11.3

4.9

18.1

11.5

170.3

170.1

170.2

40.4

40.5

40.5

191.1

19

12.0

12.2

12.1

5.2

19.7

12.5

172.3

171.7

172.0

41.8

41.7

41.8

192.8

20

13.3

12.9

13.1

6.3

21.3

13.8

174.6

173.6

174.1

43.0

41.7

42.4

194.1

21

15.1

14.2

14.7

7.2

23.5

15.4

177.1

175.7

176.4

44.0

43.0

43.5

195.3

22

16.1

15.4

15.8

8.1

25.1

16.6

179.2

177.6

178.4

45.0

44.3

44.7

196.3

23

17.0

16.6

16.8

8.7

26.6

17.7

181.2

179.1

180.2

46.4

45.5

46.0

197.6

24

17.6

17.1

17.4

9.4

27.4

18.4

182.6

180.0

181.3

47.5

45.5

46.5

198.7

25

19.5

18.4

19.0

10.7

29.5

20.1

184.9

182.3

183.6

48.8

46.7

47.8

199.8

26

20.1

19.2

19.7

11.3

30.4

20.9

186.3

183.4

184.9

50.3

48.0

49.2

201.1

27

22.4

20.6

21.5

12.3

31.5

21.9

188.1

184.7

186.4

51.7

49.2

50.5

202.3

28

22.4

20.6

21.5

12.8

31.5

22.2

188.5

185.1

186.8

51.7

49.2

50.5

202.3

29

22.4

21.3

21.9

13.4

32.4

22.9

189.3

185.7

187.5

52.8

50.0

51.4

203.5

30

22.8

22.1

22.5

13.6

33.4

23.5

190.3

186.4

188.4

53.8

51.1

52.5

204.7

31

23.5

23.3

23.4

14.4

34.8

24.6

191.6

187.8

189.7

54.5

52.1

53.3

205.7

32

24.1

24.7

24.4

15.3

35.3

25.3

192.5

188.7

190.6

54.8

52.1

53.5

206.6

33

24.9

26.0

25.5

16.0

36.7

26.4

193.6

189.9

191.8

55.5

53.3

54.4

207.6

34

25.7

26.5

26.1

16.6

37.5

27.1

194.4

190.8

192.6

55.8

53.3

54.6

208.7

35

26.2

27.7

27.0

17.2

38.9

28.1

195.3

191.8

193.6

56.6

54.6

55.6

209.9

36

26.8

28.3

27.6

18.0

39.8

28.9

195.9

192.9

194.4

56.9

55.8

56.4

211.0

37

27.3

29.2

28.3

18.6

40.3

29.5

196.8

194.0

195.4

56.9

55.8

56.4

212.0

38

27.7

29.8

28.8

19.0

41.6

30.3

197.2

194.3

195.8

57.8

57.0

57.4

213.5

39

28.4

31.0

29.7

19.6

42.3

31.0

197.9

195.3

196.6

58.1

57.0

57.6

214.3

40

31.5

32.1

31.8

20.3

43.7

32.0

199.0

197.5

198.3

58.6

58.2

58.4

215.2

41

31.5

32.1

31.8

20.9

44.3

32.6

199.0

197.5

198.3

59.0

58.2

58.6

216.0

42

31.5

33.2

32.4

21.1

45.2

33.2

199.7

197.5

198.6

59.3

59.3

59.3

216.6

43

31.5

34.3

32.9

21.6

46.3

34.0

200.7

198.8

199.8

59.3

59.3

59.3

217.3

44

31.5

34.3

32.9

21.9

46.7

34.3

201.1

199.2

200.2

59.9

60.4

60.2

217.9

45

31.5

35.2

33.4

22.4

47.9

35.2

201.4

199.2

200.3

59.9

60.4

60.2

218.4

46

31.9

35.6

33.8

22.7

48.3

35.5

202.2

200.0

201.1

59.9

60.4

60.2

219.1

47

32.7

36.6

34.7

23.4

49.6

36.5

202.8

200.6

201.7

60.5

61.5

61.0

219.8

48

33.2

37.2

35.2

23.7

50.0

36.9

203.3

201.4

202.4

60.5

61.5

61.0

219.8

49

34.3

38.0

36.2

24.7

51.7

38.2

204.2

202.3

203.3

60.5

61.5

61.0

220.6

50

34.3

38.0

36.2

24.7

51.7

38.2

204.6

202.8

203.7

60.5

61.5

61.0

220.6

51

34.6

38.7

36.7

24.7

52.9

38.8

204.9

203.3

204.1

60.5

62.8

61.7

221.3

52

35.3

39.4

37.4

25.2

53.5

39.4

205.7

203.8

204.8

60.9

62.8

61.9

221.7

53

35.8

40.4

38.1

25.5

54.0

39.8

206.0

204.3

205.2

61.3

62.8

62.1

222.4

54

36.3

41.1

38.7

26.0

55.1

40.6

206.7

204.8

205.8

61.7

64.1

62.9

223.2

55

36.8

42.0

39.4

26.0

55.6

40.8

207.2

205.3

206.3

61.7

64.1

62.9

223.2

56

36.8

42.0

39.4

26.5

56.7

41.6

207.5

205.3

206.4

62.1

65.3

63.7

224.3

Fb: Blank control

Ft: Test item

Fc: Reference control

Fa: Emulsifying agent control

Fi: Toxicity control

Table2Biodegradation (%)

Day

Fc1

Fc2

Average Fc

Ft1

Ft2

Average Ft

Fi

0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

1

28.7

28.7

28.7

0.0

0.0

0.0

15.0

2

48.2

49.0

48.6

0.0

0.0

0.0

19.5

3

58.0

58.6

58.3

0.0

1.1

0.6

27.0

4

73.0

73.6

73.3

1.4

2.1

1.7

33.7

5

77.1

77.6

77.3

2.5

3.6

3.0

36.2

6

80.6

81.2

80.9

3.6

4.7

4.1

39.0

7

83.3

84.1

83.7

4.5

5.9

5.2

40.1

8

85.4

86.4

85.9

5.3

7.1

6.2

40.6

9

87.1

88.1

87.6

6.2

8.6

7.4

41.1

10

88.3

89.1

88.7

7.0

9.7

8.3

41.5

11

89.4

90.3

89.9

8.1

10.7

9.4

41.9

12

90.7

91.2

90.9

9.1

11.4

10.2

42.2

13

91.4

92.1

91.7

9.9

11.3

10.6

42.6

14

92.4

92.9

92.6

10.8

11.4

11.1

43.0

15

92.9

93.3

93.1

11.0

11.9

11.4

43.2

16

94.0

94.1

94.0

11.6

12.0

11.8

43.6

17

94.6

94.6

94.6

12.0

12.1

12.1

44.0

18

95.3

95.2

95.3

12.0

12.0

12.0

44.1

19

95.9

95.6

95.8

12.2

12.1

12.2

44.3

20

96.5

95.9

96.2

12.1

11.6

11.9

44.3

21

97.1

96.2

96.7

11.9

11.5

11.7

44.2

22

97.6

96.6

97.1

11.8

11.5

11.6

44.1

23

98.2

96.9

97.5

11.9

11.6

11.8

44.2

24

98.6

97.0

97.8

12.1

11.3

11.7

44.3

25

98.9

97.4

98.1

11.9

11.0

11.5

44.1

26

99.3

97.6

98.4

12.2

11.3

11.8

44.2

27

99.8

97.7

98.7

12.4

11.3

11.9

44.3

28

99.8

97.8

98.8

12.3

11.2

11.8

44.2

29

99.9

97.7

98.8

12.4

11.3

11.8

44.3

30

100.1

97.8

98.9

12.6

11.5

12.0

44.5

31

100.2

98.0

99.1

12.4

11.4

11.9

44.5

32

100.4

98.1

99.2

12.3

11.1

11.7

44.5

33

100.4

98.2

99.3

12.1

11.2

11.6

44.5

34

100.5

98.3

99.4

11.9

10.9

11.4

44.6

35

100.4

98.3

99.3

11.9

11.0

11.4

44.6

36

100.2

98.4

99.3

11.6

11.2

11.4

44.7

37

100.5

98.8

99.6

11.4

10.9

11.2

44.8

38

100.2

98.4

99.3

11.4

11.1

11.3

45.0

39

100.2

98.6

99.4

11.3

10.8

11.0

45.0

40

100.2

99.3

99.8

11.0

10.9

11.0

45.0

41

99.9

99.0

99.4

11.0

10.6

10.8

45.0

42

100.0

98.6

99.3

10.9

10.9

10.9

45.0

43

100.1

98.9

99.5

10.5

10.5

10.5

45.0

44

100.1

99.0

99.5

10.6

10.8

10.7

45.1

45

99.8

98.5

99.1

10.3

10.5

10.4

45.0

46

100.1

98.7

99.4

10.1

10.3

10.2

45.1

47

99.8

98.5

99.2

10.0

10.4

10.2

45.0

48

99.9

98.8

99.3

9.8

10.2

10.0

44.9

49

99.6

98.5

99.1

9.3

9.7

9.5

44.8

50

99.9

98.8

99.3

9.3

9.7

9.5

44.8

51

99.7

98.7

99.2

9.0

10.0

9.5

44.8

52

99.8

98.7

99.3

8.9

9.7

9.3

44.8

53

99.8

98.8

99.3

8.9

9.6

9.3

44.8

54

99.7

98.6

99.2

8.8

9.8

9.3

44.8

55

99.9

98.7

99.3

8.7

9.7

9.2

44.8

56

99.6

98.3

98.9

8.5

9.8

9.2

44.8

Ft: Test item

Fc: Reference control

Fi: Toxicity control

 

Table3pH recorded

Treatment

Flask

Day 0

Day 56

Blank control 1

Fb1

7.4

7.7

Blank control 2

Fb2

7.4

7.4

Reference control 1

Fc1

7.4

7.8

Reference control 2

Fc2

7.4

7.8

Test item 1

Ft1

7.4

7.2

Test item 2

Ft2

7.4

7.2

Agent control 1

Fc1

7.4

7.3

Agent control 2

Fc2

7.4

7.4

Toxicity control

Fi

7.4

7.6

ND Not Determined

 

Theoretical oxygen demand

The theoretical oxygen demand of the test item is ThOD = 2.4080 mg O2/mg (based on its molecular formula C14H20O2provided by the Sponsor). This calculation was based on the main constituent of the mixture that represents 92.1% of the test item and is calculated by assuming formation of ammonium, water and carbon dioxide (no nitrification).

 

The theoretical oxygen demand of sodium benzoate is 1.666 mg O2/mg.

Oxygen consumption and percentage of biodegradation

All raw data are presented in Table1 and Table2.

 

With regards to the oxygen consumption, the emulsifying agent (Synperonic) could be considered as not toxic to bacteria and not biodegradable under test conditions.

 

The reference item was readily biodegradable under the conditions of the test as >60% biodegradation was achieved by Day 14; this demonstrates the acceptable viability of the inoculum.

 

The test item did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage was 43.0% (higher than 25%) after 14 days.

 

The average degradation level of the test item was 11.1% at day 28 and 9.2% at day 56.

Physical-chemical measurements

pH was measured in all flasks at the start and the end of the test period, values are shown inTable3and comprised between 7.4 and 7.8. 

 

Recorded test temperatures were between 21.3 and 22.3°C (mean: 21.6°C).

 

 

Validation criteria

The definitive test met the validity criteria of the test guideline detailed as follows:

 

§ the difference between replicate values corresponding to the removal of the test item at the end of the test was less than 20%

§ the percentage degradation of the reference compound has reached the pass levels by day 14: 92.6%

§ the biodegradation observed in the toxicity control bioreactor was not less than 25% occurred within 14 days: 43.0%

§ the oxygen uptake of the inoculum blank was not greater than 60 mg/l in 28 days: 21.5 mg/L (and 22.2 for agent control)

§ the pH value was not outside the 6-8.5 range: min 7.4, max 7.8

 

The test is thus considered as valid.


 

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Discussion/Conclusion
According to the OECD 301 guideline, the pass level for ready biodegradability is 60% of ThOD for respirometric methods. This pass value has to be reached in a 10-d window within the 28-d period of the test; the 10-d window begins when the degree of biodegradation has reached 10% ThOD and must end before day 28 of the test.
 
In this study, the 60% biodegradation of ThOD was not reached (the average degradation level of the test item was11.1% at day28and9.2% at day 56).As a consequence, the test item was not readily biodegradable under the conditions of the test.
Executive summary:

The study was conducted in accordance with procedures outlined in OECD Guideline 301F. The ready biodegradability of the test item was assessed over a 56 days period (as the biodegradation curve did not reached a plateau at day 28, the test was prolonged beyond 28 days).

 

The test was conducted at a nominal loading rate of 100 mg/L. As the test item was difficult to dissolve, its dispersibility was improved by the use of an emulsifying agent (Synperonic P103) as described in ISO 10634 standard.

 

A total of 9 bioreactors were used; 2 each for test item, blank control, reference item control, emulsifying agent control and one for toxicity control.

 

The results of the test were as follows:

 

% biodegradation

Test item

(mean of replicates)

Reference item

(mean of replicates)

Toxicity Control

At day 14

11.1

92.6

43.0

At day 28

11.8

98.8

44.2

At day 56

9.2

98.9

44.8

 

 The test item was not readily biodegradable under the conditions of the test as it failed to achieve a transition from 10% to 60% degradation in a 10-day window during the 28 days test.The average degradation level of the test item was 11.8% at day 28 and 9.2% at day 56.

 

The test item was not considered to be inhibitory to the microbial inoculum since the biodegradation observed in the toxicity control bioreactor was not less than 25% occurred within 14 days. 

 

The definitive test met the validity criteria of the test guideline detailed as follows:

 

§ the difference between replicate values corresponding to the removal of the test item at the end of the test was less than 20%

§ the percentage degradation of the reference compound has reached the pass levels by day 14: 92.6%

§ the biodegradation observed in the toxicity control bioreactor was not less than 25% occurred within 14 days: 43.0%

§ the oxygen uptake of the inoculum blank was not greater than 60 mg/l in 28 days: 21.5 mg/L (and 22.2 for agent control)

§ the pH value was not outside the 6-8.5 range: min 7.4, max 7.8

Description of key information

The biodegradability of the test substance was determined in two experimental studies performed in accordance with the OECD 301 F test guideline (manometric respirometry) and GLP requirements.


 


The substance reached up to 14.8% biodegradation at day 28 considering the results of both studies. Therefore, it is not considered readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria
Type of water:
freshwater

Additional information