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Environmental fate & pathways

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:
1992
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP laboratory study
Qualifier:
according to guideline
Guideline:
other: OECD DOC-Die away test (EG-Richtlinie 92/69 EWG, Tiel II, C.4-A)
Principles of method if other than guideline:
Equivalent to OECD 301A
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
11.3 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
A measured volume of inoculated mineral medium, containing a known concentration of the test substance (10-40 mg DOC/l) as the nominal sole source of organic carbon, is aerated in the dark or diffuse light at 22 ± 2°C. Degradation is followed by DOC analysis at frequent intervals over a 28-day period. The degree of biodegradation is calculated by expressing the concentration of DOC removed (corrected for that in the blank inoculum control) as a percentage of the concentration initially present.
Reference substance:
benzoic acid, sodium salt
Remarks:
99.5% purity
Key result
Parameter:
% degradation (DOC removal)
Value:
94
Sampling time:
28 d
Details on results:
readily biodegradable
Results with reference substance:
Biodegradation with the reference substance, sodium benzoate, at 11.8 mg DOC/L resulted in 96% degradation in 28 days.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Executive summary:

The substance was tested in a 28 -day DOC-die away test and found to be degraded by 94% in 28 days. The substance is readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Nov. 18, 2002-Dec. 19, 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Marl-Ost municipal sewage treatment plant
- Initial cell/biomass concentration: 3.94 g/l dry matter
Duration of test (contact time):
29 d
Initial conc.:
34.3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Test temperature: 19.7-21.9 degree C
- pH: 7.4-7.5
- Aeration of dilution water: yes, overnight
- Suspended solids concentration: 26.3 mg/L

TEST SYSTEM
- Culturing apparatus: 5000 ml Woullf flasks
- Number of culture flasks/concentration: 2 flasks

SAMPLING
- Sampling frequency: 0, 2, 5, 9, 12, 14, 21, 28, and 29 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks

STATISTICAL METHODS: Results were calculated using the EXCEL computer program.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
85
Sampling time:
29 d
Details on results:
The test substance was 85% degraded on day 29.
Results with reference substance:
The reference substance was 89% degraded in 29 days.

% Degradation

Test Duration
(days)
Sodium Benzoate Test Vessel 1 Test Vessel 2 Test Vessel Mean
0 0 0 -1 -1
2 32 1 -5 -2
5 59 24 19 22
9 76 57 46 52
12 84 73 66 70
14 84 72 67 70
21 93 76 79 78
28 95 86 80 83
29 89 84 85 85
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance was 85% degraded in 29 days, and is considered readily biodegradable.
Executive summary:

This study examined the biodegradability of the test substance. 34.3 mg/L of test substance was added to flasks containing activated sludge. The amount of CO2 evolved was then measured over the next 29 days. Sodium benzoate was used as a reference substance. The reference substance was 89% degraded in 29 days. Therefore the test is valid. The test substance was 85% degraded in 29 days. The test substance is readily biodegradable.

Description of key information

The key study examined the biodegradability of LAS-acid. The substance (initial concentration at 11.3 mg/L DOC) was tested in a 28 -day DOC-die away test and found to be degraded by 94% in 28 days. The substance is readily biodegradable. The supporting study examined the biodegradability of LAS. The amount of CO2 evolved was measured over 29 days. The test substance was 85% degraded in 29 days. The reference substance (sodium benzoate) was 89% degraded in 29 days. Thus, the LAS is readily biodegradable as well.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information