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Biodegradation in water: screening tests

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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.
Justification for type of information:
Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, aromatics (2-25%) straddles Hydrocarbons, C9-C14, Aliphatics, (2-25% Aromatics) and Hydrocarbons, C14-C20, Aliphatics (2-30% Aromatics). Read across justification documents have been provided for the same in Section 13 of the dossier. For this substance, a worst case scenario approach has been used for each endpoint.
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.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
22-Aug-1994 to 23-Sep-1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was given a reliability of 1, because it followed an OECD standard guideline, which describes a procedure specifically designed to evaluate this endpoint, and the results were reviewed for reliability and assessed as valid.
Justification for type of information:
Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, aromatics (2-25%) straddles Hydrocarbons, C9-C14, Aliphatics, (2-25% Aromatics) and Hydrocarbons, C14-C20, Aliphatics (2-30% Aromatics). Read across justification documents have been provided for the same in Section 13 of the dossier. For this substance, a worst case scenario approach has been used for each endpoint.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum used as the source of the microorganisms was an aliquot of fresh activated sludge from a domestic wastewater treatment facility in New Jersey, USA.
Duration of test (contact time):
28 d
Initial conc.:
ca. 35 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Activated sludge and test medium were combined prior to test substance addition. Test medium consisted of glass-distilled water and mineral salts (Phosphate buffer, Ferric chloride, Magnesium sulfate, Calcium chloride). Test vessels were 1L glass flasks located in a waterbath and electronically monitored for oxygen consumption. Test temperature was 21 +/- 1 Deg C. All test vessels were stirred constantly for 28 days using magnetic stir bars and plates.

Test material was tested in triplicate, controls and blanks were tested in duplicate. The amount of oxygen consumed by microorganisms from the oxidation of the test material was continuously monitored by an automated respirometer during the 28-day test period. Test material concentration was 35mg/L. Sodium benzoate (positive control) concentration was 50mg/L. All test vessels were stirred constantly for 28 days using magnetic stir bars and plates.
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
15.4
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
50.4
Sampling time:
11 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
60.7
St. dev.:
2.77
Sampling time:
28 d
Details on results:
Test material was readily biodegradable, but failed the 10-day window. The biodegradation half-life was <2 weeks. On day 28, 60.7% degradation of the test substance was observed. 10% biodegradation was achieved on approximately day 4, 50% on approximately day 11, and 60% on day 27. By day 3, >60% biodegradation of the positive control was observed. No excursions from the protocol were noted.

The study was extended to Day 31, where the test substance achieved a mean percent biodegradation of 61.5%.
Results with reference substance:
Sodium benzoate, the positive control, achieved 99.0% degradation after 14 days, and therefore this test may be considered valid. On Day 28 of the study, the mean percent degradation of the positive control was 88.7%.

Biodegradation was based on oxygen consumption and the theoretical oxygen demand of the test material as calculated using results of an elemental analysis of the test material.

 

 

% Degradation*

Mean % Degradation

Sample

(day 28)

(day 28)

Test Material

66.8, 56.2, 59.1

60.7

Na Benzoate

89.9, 87.5

88.7

 

* replicate data

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%), a multi-component substance, biodegraded to an extent of 61% after 28 days. The data support characterizing the test substance as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.
Executive summary:

Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2 -30%), a multi-component substance, biodegraded to an extent of 61% after 28 days. The data support characterizing the test substance as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.

Description of key information

There is no data available for Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, 2-25% aromatics. Data is read across from structural analogues such as Hydrocarbons, C9-C14 aliphatics, 2-25% aromatics and Hydrocarbons, C14-C20 aliphatic, 2-30% aromatics. Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, aromatics (2-25%) straddles Hydrocarbons, C9-C14, Aliphatics, (2-25% Aromatics) and Hydrocarbons, C14-C20, Aliphatics (2-30% Aromatics). Read across justification documents have been provided for the same in Section 13 of the dossier. For this substance, a worst case scenario approach has been used for each endpoint.

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.

C14-C20 Aliphatics (2-30% Aromatics), multi-component substances, biodegraded to an extent of 61% after 28 days in an OECD 301F study. The data support characterizing the test substance(Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics(2 -30%)) as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.

These data are used as read across data for Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, 2-25% aromatics.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information