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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:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
Not available
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
test was run for 31 days
GLP compliance:
yes (incl. QA statement)
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): Somerset-Raritan Valley Sewage Authority, Bridgewater, New Jersey
- Storage length: sludge was obtained one day before the test
- Preparation of inoculum for exposure: sludge was homogenized by mixing in a blender at medium speed for 2 min. It was then allowed to settle for 30 min. The supernatent was decanted, and the filtered supernatent used to determine microbial activity
- Pretreatment: 24 L of distilled water was placed in a 50 L carboy. The following solutions were added: 24 mL of magnesium sulfate, 24 mL of calcium chloride, 240 mL phosphate buffer, 24 mL ferric chloride, and 240 mL of sludge supernatent. The carboy was then aerated for 24 h with CO free air.
- Initial cell/biomass concentration: 10^6 colony forming units/mL
- Water filtered: yes
- Type and size of filter used, if any: glass
Duration of test (contact time):
31 d
Initial conc.:
32.5 mg/L
Based on:
test mat.
Initial conc.:
38.5 mg/L
Based on:
test mat.
Initial conc.:
36.1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: 24 mL of magnesium sulfate, 24 mL of calcium chloride, 240 mL phosphate buffer, 24 mL ferric chloride, and 240 mL of sludge supernatent in distilled water
- Test temperature: 22±1 °C
- Aeration of dilution water: aerated for 24 h prior to test

TEST SYSTEM
- Number of culture flasks/concentration: 3
- Measuring equipment: electrolytic respirometer from Co-ordinated Environmental Service, Kent, England
- Test performed in closed vessels due to significant volatility of test substance: yes
- Details of trap for CO2 and volatile organics if used: manometric cell/CO2 trap

SAMPLING
- Sampling frequency: hourly
- Sampling method: aerobic respirometer

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes

STATISTICAL METHODS: Results were analysed using Lotus v2.2
Reference substance:
benzoic acid, sodium salt
Remarks:
5.0 mL of a 6,115 mg C/L solution
Parameter:
% degradation (O2 consumption)
Value:
13.8
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
60
Sampling time:
11 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
74.7
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
75.9
Sampling time:
31 d
Results with reference substance:
The reference substance was degraded > 60%, therefore the test is valid.

Table: Daily Percent Biodegradation

Day

Average % Degradation of Sodium Benzoate

Average % Degradation of Test Material

1

21.5

0

2

55.4

1.52

3

64.3

7.81

4

72.7

13.8

5

77.5

21.9

6

80.4

28.8

7

83.3

34.2

8

87.4

39.8

9

94.1

45.8

10

99.0

52.9

11

101.2

60.0

12

102.0

64.3

13

101.4

67.1

14

99.0

68.0

15

96.0

67.7

16

92.9

67.2

17

91.5

67.6

18

90.7

68.1

19

90.2

68.8

20

89.8

69.4

21

89.7

70.2

22

89.5

70.9

23

89.4

71.6

24

89.2

72.3

25

89.1

73.0

26

88.9

73.6

27

88.8

74.1

28

88.7

74.7

29

88.6

75.2

30

88.5

75.6

31

88.5

75.9

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance biodegraded to an extent of 74.7% after 28 days with an unacclimated sewage sludge inoculum. The test substance was determined to be readily biodegradable.
Executive summary:

The purpose of this study was to determine the ready biodegradability of Hydrocarbons, C10-C13, n-alkanes, isoalkanes, cyclics, 2-25% aromatics. 35 mg/L of test substance was added to test vessels inoculated with activated sludge. The oxygen consumption of the sludge was then monitored for 31 days. Sodium benzoate was used as a reference substance. The reference substance was 88.7% degraded in 28 days, therefore the test is valid. The test substance was 74.7% degraded by day 28 and met the 10 -day window requirement for >60% degradation. The test substance is readily biodegradable.

Description of key information

There is no data available for this substance. However, key data is available for the structural analogue Hydrocarbons, C10-C13, n-alkanes, isoalkanes, cyclics, aromatics (2-25%) and is presented in the dossier. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

Key information is summarised below:

Hydrocarbons, C10-C13, n-alkanes, isoalkanes, cyclics, aromatics (2-25%) biodegraded to an extent of 74.7% after 28 days with an unacclimated sewage sludge inoculum. The test substance was therefore determined to be readily biodegradable.  

Based on the available data, this substance is considered readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information