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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study (OECD 302 C)
Qualifier:
according to
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Deviations:
no
GLP compliance:
not specified
Specific details on test material used for the study:
Batch Number 2,4-AP/307
Oxygen conditions:
aerobic
Inoculum or test system:
other: a mixed population of activated sewage sludge microorganisms
Details on inoculum:
- Source of inoculum: Activated sewage was prepared by sampling 10 different sites around the UK in accordance with OECD Guideline No. 302C
- Preparation: the mixed sludge was fed daily with 0.1% synthetic sewage and maintained on a constant aeration at 25 ± 1C
- Usage rate: equivalent to 100 mg dry weight/l
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
- Test temperature: 25 ± 1C
- Aeration of dilution water: constant
- Continuous darkness: yes
- Agitation: by magnetic stirrers
- Criteria: oxygen consumption measured by direct manometer reading
- Observations: manometer volumes were recorded daily
Reference substance:
aniline
Test performance:
TOC analysis of phenol, 2,4-bis (1,1 -dimethylethyl) was not possible due to the insoluble nature of the test material.
A modified Miti test was carried out due to the insoluble nature of the test material.
A COD value of 2.85 mg O2/mg was obtained for the test material.
For % degradation calculation a ThOD of 2.95 mg O2/mg was used based on the following approximate values:
Molecular formula: C14H22O
Molecular weight: 206
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
% Biodegradation
0% 0-28 days
All % Biodegradation values have been corrected for blank values
Parameter:
COD
Value:
2.85 other: mg O2/mg test material
Results with reference substance:
Aniline attained 74% biodegradation after 14 days thereby confirming the suitability of the inoculum and culture conditions. Aniline attained 4% degradation within 7 days. However this is not considered to affect the overall integrity of the study given that aniline attained 74% degradation within 14 days. Total organic carbon analysis of the test media at day 0 and day 28 showed that aniline attained 87% degradation within 28 days.

Day

% Biodegradation

Phenol 2,4-bis

(1,1-dimethylethyl)

Aniline

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

2

4

12

17

18

41

64

73

74

73

74

81

86

86

80

90

89

87

86

83

81

81

88

Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
Phenol, 2,4-bis (1,1-dimethylethyl)- attained negligible degradation within 28 days calculated from oxygen uptake (% of COD and ThOD) and , therefore, cannot be considered as inherently biodegradable under the strict terms and conditions of the OECD Guidelines
Executive summary:

The inherent biodegradability of the test substance phenol 2,4 -bis(1,1 -dimethylethyl) was evaluated. The method used followed that described in the OECD Guidelines for Testing of Chemicals / Section 2: Degradation and Accumulation, Test No. 302C "Inherent Biodegradability, Modified MITI Test (II). A mixed population of activated sewage sludge microorganisms was used as inoculum and aniline as reference substance. Initial concentration of test substance was 30 mg/l and reference substance 100 mg/l. Phenol 2,4 -bis(1,1-dimethylethyl) attained negligible degradation within 28 days calculated from oxygen uptake (% of COD and ThOD) and so, therefore, cannot be considered as inherently biodegradable under the strict terms and conditions of the OECD Guidelines. TOC analysis of phenol 2,4 -bis(1,1-dimethylethyl) was not possible due to the insoluble nature of the test material. A modified Miti test was carried out due to this fact. A COD value of 2.85 mg O2/mg was obtained for the test material.

Description of key information

Negligible degradation within 28 days (% of COD and ThOD), cannot be considered as inherently biodegradable (OECD 302 C).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Two studies have been conducted which assess biodegradability in water (activated sludge respiration inhibition test).

1. Inherent biodegradability, Modified MITI Test (II). (OECD 302C)

2. BOD-Test for Insoluble Substances

In the first test, the inherent biodegradability of 2,4-DTBP was evaluated. The method used followed that described in the OECD Guidelines for Testing of Chemicals / Section 2: Degradation and Accumulation, Test No. 302C "Inherent Biodegradability, Modified MITI Test (II). A mixed population of activated sewage sludge microorganisms was used as inoculum and aniline as reference substance. Initial concentration of test substance was 30 mg/l and reference substance 100 mg/l. 2,4-DTBP attained negligible degradation within 28 days calculated from oxygen uptake (% of COD and ThOD) and therefore, cannot be considered as inherently biodegradable under the strict terms and conditions of the OECD Guidelines. TOC analysis of 2,4-DTBP was not possible due to the insoluble nature of the test material. A modified MITI test was carried out due to this fact. A COD value of 2.85 mg O2/mg was obtained for the test material.

In the second test, 2,4-DTBP was evaluated for its biodegradability according to ISO Draft (BOD Test for Insoluble Substances). Test substance, 6.3, 7.6 and 6.8 mg, 2,4-DTBP/flask and reference substance, diethylene glycol (13.8, 13.8 and 13.7 mg/flask) were weighed into flasks and samples were taken weekly over 28 days to measure the oxygen content.

The test material attained negligible degradation (2%) within 28 days calculated from oxygen uptake (% of ThOD) and therefore, cannot be considered as biodegradable.