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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:
Not available
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
test was run for 31 days
GLP compliance:
yes (incl. certificate)
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, C11-C14, 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

Hydrocarbons, C10-C13, n-alkanes, isoalkanes, cyclics, aromatics (2-25%), biodegraded 75% after 28 days under the conditions of the study and is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information