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Environmental fate & pathways

Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
The inoculum was sourced from a domestic sewage tretament plant and assumed non-adapted. The MLSS was 2200 mg/L and the sludge was kept under aerobic conditions until use the day after collection.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
- Composition of medium: Mineral medium as detailed in the OECD 301F guideline
- Additional substrate: None
- Solubilising agent (type and concentration if used): None
- Test temperature: 22 ± 1°C
- pH: 7.4 to 7.5 for test suspensions
- pH adjusted: No
- Aeration of dilution water: Not directly although aerobic conditions were maintained
- Suspended solids concentration: 30 mg/L
- Continuous darkness: Not detailed

- Sampling frequency: Continuously
- Sampling method: Closed system automatic measuring apparatus

- Inoculum blank: Two vessels included (inoculum + media)
- Abiotic sterile control: None included
- Procedural control: One vessel included (inoculum + media + sodium benzoate)
- Toxicity control: One vessel included (inoculum + media + test substance + sodium benzoate)

STATISTICAL METHODS: None employed (not usually required for this study type)
Reference substance:
benzoic acid, sodium salt
Test performance:
The biodegradability test was judged to be valid since all validity criteria of the test guideline were met.
% degradation (O2 consumption)
Sampling time:
28 d
Results with reference substance:
Procedure control: 86% degradation by 7 Days rising to 90% degradation on day 28.
Toxicity control: 33% degradation by 7 Days rising to 39% degradation on day 28 (shows slight inhibition but need deemed to be fully inhibitory in relation to the guideline requirements (i.e. > 25% degradation observed from Day 14 of the test in toxicity control)).
Validity criteria fulfilled:
Interpretation of results:
not readily biodegradable
In a OECD guideline study, it was concluded that the test substance is not readily biodegradable with 0% biodegradation observed after 28 days.

Description of key information

A ready biodegradation test was performed in accordance with the OECD 301F guideline. The test showed 0% biodegradation after 28 days of exposure and accordingly the test substance is considered not to be readily biodegradable under the conditions of the test.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information