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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:
04 Oct - 14 Nov 2016
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)
Version / remarks:
1992
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
2008
GLP compliance:
yes (incl. certificate)
Remarks:
Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: wastewater plant treating predominantly domestic sewage (Wupper area water authority, WWTP Odenthal); sampling date: 04 Oct 2016
- Storage conditions: at room temperature under continuous stirring with aeration
- Storage length: stored for one day
- Preparation of inoculum for exposure: was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant;
- Pretreatment: aliquot of the wet sludge was dried in order to determine the wet weight / dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L. Calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume
- Concentration of sludge: 30 mg/L suspended solids
- Water filtered: no
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Remarks:
ThOD of the test substance: 0.969 mg O2/mg
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: according to OECD 301 F
- Test temperature: constant temperature (22 ± 1 °C)
- pH: 7.4 - 8.1
- Suspended solids concentration: 30 mg/L suspended solids
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: OxiTopControl System (WTW)
- Number of culture flasks/concentration: 10 flasks (test item: 4 replicates; inoculum blank: 3; reference control: 2 replicates; toxicity control: 1 replicate)
- Measuring equipment: oxygen consumption was determined by measuring the drop in pressure in the automated respirometer flasks. Evolved carbon dioxide was absorbed in sodium hydroxide. The amount of oxygen taken up by the test item was expressed as a percentage of theoretical oxygen demand (ThOD)
- Test performed in closed vessels: yes

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3
- Toxicity control:1
- Reference control: 2

Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
1
Sampling time:
28 d
Details on results:
Within 28 days, a degradation rate of 1 % was determined for the test item. The test item is considered to be "Not Readily Biodegradable".
Oxygen uptake by nitrification: The oxygen consumed by nitrification was not determined at the end of the study, because no degradation of the test item was observed and the correction for oxygen uptake by nitrification would not have an influence on the results.
Toxicity control: The used concentration of the test item is not toxic to bacteria since degradation rates was 54 % after 14 days
Biological results are summarized in Table 1-3 in section"Any other information on results incl. tables"
Results with reference substance:
The reference compound sodium benzoate showed 85 % degradation after 14 days.

Tabel 1: Degradation of test item

Test concentration : 100 mg/L

Theoretical oxygen demand : 0.969 mg O2/mg

time [d]

blank-corrected BOD (a –bm) [mg O2/L]

% degradation

% degradation mean

a1

a2

a3

a4

a1

a2

a3

a4

0

0.0

0.0

0.0

0.0

0

0

0

0

0

1

1.5

1.5

1.5

0.1

1

1

1

0

1

2

2.1

2.1

2.1

0.7

2

2

2

1

2

3

1.4

1.4

1.4

1.4

1

1

1

1

1

4

1.4

0.0

1.4

0.0

1

0

1

0

1

5

0.7

0.7

2.1

0.7

1

1

2

1

1

6

1.4

0.0

2.8

1.4

1

0

3

1

1

7

0.0

0.0

1.4

0.0

0

0

1

0

0

8

1.4

1.4

2.8

0.0

1

1

3

0

1

9

0.7

0.7

2.1

0.7

1

1

2

1

1

10

0.0

0.0

2.8

0.0

0

0

3

0

1

11

1.4

0.0

2.8

0.0

1

0

3

0

1

12

0.7

0.0

2.1

0.7

1

0

2

1

1

13

0.7

0.7

2.1

0.7

1

1

2

1

1

14

0.0

0.0

2.8

0.0

0

0

3

0

1

15

0.0

0.0

2.1

0.7

0

0

2

1

1

16

0.7

0.7

2.1

0.0

1

1

2

0

1

17

0.0

0.0

1.4

0.0

0

0

1

0

0

18

0.0

0.0

1.4

0.0

0

0

1

0

0

19

1.4

0.0

2.9

0.0

1

0

3

0

1

20

1.4

0.0

2.9

1.4

1

0

3

1

1

21

0.8

0.0

0.8

0.8

1

0

1

1

1

22

0.1

0.1

1.5

0.1

0

0

1

0

0

23

0.1

0.1

1.5

0.0

0

0

1

0

0

24

0.1

0.1

1.5

0.1

0

0

1

0

0

25

0.0

0.0

1.5

0.0

0

0

1

0

0

26

0.8

0.0

2.2

0.0

1

0

2

0

1

27

0.8

0.0

0.8

0.8

1

0

1

1

1

28

0.8

0.0

2.2

0.8

1

0

2

1

1

Table 2: Degradation of reference compound

Test concentration : 100 mg/L

Theoretical oxygen demand : 1.665 mg O2/mg

time [d]

blank-corrected BOD (r –bm) [mg O2/L]

% degradation

% degradation mean

 

r1

r2

r1

r2

 

0

0.0

0.0

0

0

0

1

45.1

42.3

27

25

26

2

81.0

79.6

49

48

48

3

104.3

104.3

63

63

63

4

113.9

113.9

68

68

68

5

120.2

120.2

72

72

72

6

125.5

125.5

75

75

75

7

128.1

128.1

77

77

77

8

131.1

132.1

79

79

79

9

133.4

134.4

80

81

80

10

135.7

135.7

82

82

82

11

136.7

136.7

82

82

82

12

137.0

137.0

82

82

82

13

140.0

140.0

84

84

84

14

141.3

141.3

85

85

85

15

140.6

141.6

84

85

85

16

141.6

141.6

85

85

85

17

141.9

140.9

85

85

85

18

141.9

141.9

85

85

85

19

143.9

143.9

86

86

86

20

143.9

144.9

86

87

87

21

144.8

144.8

87

87

87

22

144.1

145.1

87

87

87

23

145.1

145.1

87

87

87

24

145.1

145.1

87

87

87

25

146.1

146.1

88

88

88

26

145.4

145.4

87

87

87

27

145.4

147.4

87

88

88

28

147.4

147.4

88

88

88

 

Table 3: Degradation of toxicity control

Test concentration test item : 100 mg/L

Theoretical oxygen demand : 0.969 mg O2/mg

Test concentration reference compound : 100 mg/L

Theoretical oxygen demand : 1.665 mg O2/mg

time [d]

blank-corrected BOD (t –bm) [mg O2/L]

% degradation

 

t1

t1

0

0.0

0

1

46.6

18

2

81.0

31

3

111.3

42

4

120.9

46

5

126.2

48

6

131.5

50

7

134.1

51

8

137.1

52

9

138.4

53

10

139.7

53

11

140.7

53

12

142.0

54

13

143.0

54

14

143.3

54

15

142.6

54

16

144.6

55

17

144.9

55

18

144.9

55

19

146.9

56

20

147.9

56

21

145.8

55

22

146.1

55

23

146.1

55

24

148.1

56

25

148.1

56

26

148.4

56

27

148.4

56

28

150.4

57

 

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed

Description of key information

Not readily biodegradable according to the OECD criteria (1% degradation after 28 d, OECD 301 F).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

One biodegradation screening study according to OECD 301 F (GLP) is available for the substance (M-571269-01-1). Non-adapted, domestic activated sludge from a sewage treatment plant was used as inoculum. The test item was found to be not readily biodegradable under the test conditions at the end of the 28 -day exposure period. A toxicity control containing both, reference substance and test substance, did not indicate inhibitory effects to the inoculum (54% degradation after 14 d). All validity criteria of the study were met.