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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:
1994-09-12 to 1994-11-21
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
- Source of inoculum: secondary effluent of a treatment plant
- Preparation of inoculum for exposure: the effluent was centrifuged for 20 minö at 4000 g at ca. 20°C
- Concentration of the inoculum: 5 x 10E5 bact/mL
- Initial cell/biomass concentration in the test system: 5 x 10E3 bact/mL
Duration of test (contact time):
28 d
Initial conc.:
17.55 mg/L
Based on:
COD
Parameter followed for biodegradation estimation:
DOC removal
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (DOC removal)
Value:
ca. 96
St. dev.:
1
Sampling time:
28 d
Parameter:
% degradation (DOC removal)
Value:
ca. 92
St. dev.:
0.5
Sampling time:
10 d
Parameter:
% degradation (DOC removal)
Value:
ca. 62
St. dev.:
34
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
ca. 8
St. dev.:
0.5
Sampling time:
3 d
Details on results:
Toxicity control attained 93% degradation after 10 days and 97% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions. Adsorption of the test substance to the test vessels was not observed during the test course. The difference of extremes of replicate values of the removal of the test chemical at the plateau and at the end of the test is less than 20%. The percentage degradation of the reference compound has reached the pass level by day 14. Therefore, the test can be considered as valid.

The 10-d window started on day 7 (62% DOC removal). The ready biodegradability pass level of 70% DOC removal was passed already on day 10 (92%).

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
After the 28 d study period 96% of the test item were degraded (DOC removal) and the requirement of the 10 d window was fulfilled. Therefore, 3 -mercaptoproporionic acid can be considered as readily biodegradable.

Description of key information

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

3-MPA was tested for its ready biodegradability in water in a 28 d DOC Die-Away test under GLP by Thiebaud (1994). The test resulted in a final degradation rate of 96% based on the DOC removal and the 10 d window was respected. Thus, the test item can be characterized as readily biodegradable.