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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:
22 May - 20 Jun 2017
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
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Version / remarks:
1998
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss Federal Office of Public Health, Bern, Switzerland
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): The activated sludge was obtained from the aeration stage of wastewater treatment plant "ARA Birs", Birsfelden, Switzerland.
- Preparation of inoculum for exposure: The sludge was washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid phase in tap water and finally in mineral medium.
- Storage length: 1 d
- Storage conditions: Sludge was aerated at room temperature.
- Concentration of sludge: 30 mg dry material/L
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Initial conc.:
235 mg/L
Based on:
COD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline, prepared in purified water
- Test temperature: 22 - 23 °C in a thermostatic cabinet
- pH: 7.4 (test start), 7.4 - 7.8 (test end)
- pH adjusted: The pH of the test medium was adjusted from 7.8 to 7.4 with a diluted hydrochloric acid solution.
- Suspended solids concentration: 30 mg/L
- Continuous darkness: no, diffuse lighting

TEST SYSTEM
- Culturing apparatus: GL45 laboratory glass bottles (volume: 500 mL; fill volume: 164 mL; headspace: 336 mL), air-tight closed with OxiTop measuring heads.
- Number of culture flasks/concentration: 2
- Measuring equipment: OxiTop measuring heads
- Test performed in closed vessels: yes
- Details of trap for CO2 and volatile organics if used: CO2 was absorbed by an alkali trap.

SAMPLING
- Sampling frequency: BOD values were recoreded automatically every three hours.
- Sampling method: No sampling was necessary since the gas pressure reduction was measured continuously.
- Sterility check if applicable: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, two replicates
- Abiotic sterile control: no
- Toxicity control: yes, 1 replicate
- Other: procedure control: yes, 2 bottles
Reference substance:
benzoic acid, sodium salt
Remarks:
Tested at a concentration of 100 mg/L.
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Results with reference substance:
The reference item was degraded by an average of 67 and 87% after 3 d and 14 d, respectively(≥ 60 % degradation after 14 d). After 28 d the reference item was degraded to 91%.

Table 1: % degradation of the test item

 

Percent degradation

Test item

Reference substance

Toxicity control

Replicate

Replicate

Replicate

1

2

1

2

1

0

0

0

0

0

0

1

-1

0

26

25

11

2

-1

1

48

46

19

3

-2

0

67

68

28

4

-2

-1

73

73

29

5

-2

-1

76

76

30

6

-2

-1

77

79

31

7

-2

-1

79

79

32

8

-3

-2

79

80

32

9

-2

-1

81

84

33

10

-3

-1

82

84

33

11

-3

-1

84

85

34

12

-2

-1

85

85

34

13

-3

-1

85

87

35

14

-2

-1

87

87

35

15

-3

-1

88

87

35

16

-3

-1

88

88

35

17

-3

-1

89

88

35

18

-3

-1

89

88

35

19

-2

-1

90

89

36

20

-2

-1

91

89

35

21

-3

-1

91

89

36

22

-2

-1

92

90

36

23

-2

0

91

91

36

24

-3

-1

92

91

36

25

-3

0

92

92

36

26

-2

0

92

92

36

27

-2

0

92

92

37

28

-3

-1

91

91

36

Table 2: Validity criteria

Criterion from the guideline

Outcome

Validity criterion fulfilled

Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.

Not applicable since no biodegradation was recorded.

Not applicable

Percentage degradation of the reference compound has reached the pass levels by day 14.

67% after 14 d

yes

The oxygen uptake of the inoculum blank is normally 20-30 mg O2/L and should not be greater than 60 mg/L in 28 days.

17 mg/L

yes

 

Validity criteria fulfilled:
yes
Remarks:
For further details please refer to “Any other information on results incl. tables”.
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The available study was performed according to OECD 301F (GLP). After 28 days, no biodegradation was recorded. Consequently, the substance is considered to be not biodegradable under the test conditions within 28 days. The study is valid since all validity criteria were met. Moreover, the test item is not inhibitory to the inoculum since significant degradation was recorded in the toxicity control (≥ 25% degradation by Day 14).

Description of key information

Not biodegradable: 0% after 28 d (O2 consumption, OECD 301F)

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

One experimental study is available investigating the biodegradation of the substance. The study was performed according to OECD 301F (GLP) using activated sludge from a domestic sewage treatment plant (non-adapted). 100 mg/L (235 mg/L based on COD) of the substance was tested and the O2 consumption was measured automatically every 3 h for 28 d. In addition a toxicity control was prepared containing test item and reference substance (benzoic acid, sodium salt) in order to assess possible toxic effects of the test item to the inoculum.
After 28 days no biodegradation was recorded (0%). Thus, the substance is not readily biodegradable according to the OECD criteria. In the toxicity control a biodegradation of 36% was recorded indicating that the substance is not inhibitory to the inoculum.