Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2011-08-22 to 2011-11-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 301 F with GLP compliance. All validity criteria were fulfilled and no deviations were observed.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Remarks:
GLP compliance inspected on 26 and 27 October 2010 / signed on 08 February 2011
Specific details on test material used for the study:
No additional information
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
Dry weight of suspended solids : 4,38 g/L, diluted to 1,53 g/L.
To obtain a concentration of 30 mg/L (dry weight) in 103 mL flasks, 2,00 mL of sludge were added (inoculum).
To obtain a concentration of 30 mg/L (dry weight) in 255 mL flasks, 5,00 mL of sludge were added (inoculum).
Duration of test (contact time):
48 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: compliant with recommendations of TG on mineral medium
The pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Solubilising agent (type and concentration if used): None
- Test temperature: 21.9 °C - 22.7 °C
- CEC (meq/100 g): No data
- Aeration of dilution water: No data
- Suspended solids concentration: 30 mg/L dry weight activated sludge
- Continuous darkness: No data
- Water: The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

TEST SYSTEM
- Culturing apparatus: Test flasks of the Oxitop
- Number of culture flasks/concentration: 2
- Measuring equipment: The respirometer used during this study is a Oxitop Control System, made by Wissenschaftlich-Tennische Werkstätten (WTW), Weilheim, Germany.
- Test performed in closed vessels: Yes
- Test performed in open system: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Procedure control: Yes with the reference substance
- Toxicity control: No
Reference substance:
benzoic acid, sodium salt
Preliminary study:
None
Test performance:
Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked. At the end of the test period (normally 28 days), the pH of each flask is measured again.
Key result
Parameter:
% degradation (O2 consumption)
Value:
81
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
78
Sampling time:
48 d
Details on results:
Test substance undergoes 81% biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled (39% biodegradation on day 3 and 74% biodegradation on day 13).
Test substance at 30 mg/L is not considered inhibitory to the micro-organisms because the test substance did not inhibit the intrinsic respiration of the inoculum at the test concentration.
Results with reference substance:
Degradation of sodium benzoate exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum was thus verified (validity criterion).

Table 5.2.1/2: Test substance - O2 uptake (mg O2/L), adjusted to nominal concentrations

 

Days :

2

3

7

13

21

28

48

O2 uptake of sludge (inoculum blank)

1a

B1

18.8

21.5

28.3

35.0

40.4

44.4

57.9

2a

B2

17.5

20.2

26.9

32.3

36.3

39.0

44.4

mean

B

18.2

20.9

27.6

33.7

38.4

41.7

51.2

O2 uptake of Test Subst. + sludge

15a

C1

24.2

47.1

68.7

82.1

90.2

94.2

102.0

16a

C2

22.9

45.8

68.6

82

88.7

94.1

101.9

O2 uptake of Test Substance

 

C1-B

6.1

26.8

41.1

48.5

51.9

52.5

50.9

 

C2-B

4.7

24.9

41.0

48.4

50.4

52.4

50.8

% of biodegradation of test substance

 

D1

9

40

63

74

80

81

78

 

D2

7

38

63

74

77

81

78

mean

D

8

39

63

74

79

81

78

Calculations :

B1, B2, C1, C2, A1, A2, E1 : experimental O2 uptake values

B = (B1 + B2) / 2

D1 = 100 * (C1 - B) / ThOD * [S]

D2 = 100 * (C2 - B) / ThOD * [S]

D = (D1 + D2) / 2

[S] : initial test substance concentration (mg/L)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item undergoes 81 % biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled. Thus, the test item should be regarded as readily biodegradable according to this test. In addition, no toxic effects of the test substance were observed to migro-organisms at the test concentration.
Executive summary:

The ready biodegradability of the test item has been determined by the Manometric Respirometry Test according to the OECD Guideline No. 301F with GLP compliance.

A nominal concentration of test substance (30 mg/L) was introduced into the system.

The test substance was not found to be inhibitory to the micro-organisms at a concentration of 30 mg/L. The test item undergoes 81 % biodegradation after 28 days under the test conditions.

The 10 -day window criterion is also fulfilled (39 % biodegradation on day 3 and 74 % biodegradation on day 13).

Degradation of sodium benzoate exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified as acceptable.

 

According to this test, the conclusion is that the test item should be regarded as readily biodegradable.

Description of key information

OECD Guideline 301F, GLP, key study, validity 1:

81% biodegradation after 28 days within the 10-day window.

Readily biodegradable.

Non-toxic to microorganisms up to 30 mg/L.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

This study was performed on the registered substance according to OECD Guideline 301F and GLP. The test substance at 30 mg/L was inoculated with activated sludge from a wastewater treatment plant, treating predomantly domestic wastewater.The degradation of the test substance was assessed by the determination of the oxygen consumption.At the end of the 28-day exposure period, the mean biodegradation of the test substance amounted to 81% within the 10 -day window. Therefore, the test substance is considered readily biodegradable. In the toxicity control, containing both the test substance and the reference substance (sodium benzoate), the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 30 mg/L. In the procedure controls, the reference substance was degraded by an average of 91% by Exposure Day 14, and reached an average biodegradation of 96% by the end of the test (Day 28), thus confirming suitability of the activated sludge.