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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
other: NEN 6515: Water-Repetitve biodegradability test of organic compounds (1989)
GLP compliance:
yes
Specific details on test material used for the study:
- Appearance: White crystalline solid
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
Inoculum: Activated sludge sampled at De Bilt municipal sewage plant 21-02-1991
Inoculum addition: 10 mL of activated sludge, corrected to 2 g/L dry substance, per liter of test medium
Incubation temperature: 20±1.5°C
Duration of test (contact time):
49 d
Initial conc.:
22.2 mg/L
Based on:
other: ThOC
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
acetic acid, sodium salt
Test performance:
Oxidation of sodium-acetate: After 1 week 68% (required >60%) and after 4 weeks 69% (required <100%)
Oxidation consumption in the blanks: In the first week 1.2 mg (required <3mg) and in the next weeks 0.5-1.1 mg (required <1 mg)
Oxygen contents in reference test bottles (sodium acetate); apreading in triplicate values: 0-0.8 mg/L (required <1 mg/L)
Key result
Parameter:
% degradation (O2 consumption)
Value:
13
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
17
Sampling time:
49 d
Details on results:
Toxicity check-ups show the absence of any toxicity of the test substance to the inoculum: Mean oxygen content in the reference (week 1) was 4.5 mg/L and the in the toxicity bottles 4.3 mg/L
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable

Description of key information

The test substance is considered to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

The biodegradability of the test substance was tested in a ready biodegradation test performed in accordance with NEN 6515: Water Repetitive biodegradability test of organic compounds (1989) and following GLP. Inoculum from a municipal sewage treatment plant was used. Sodium acetate was used a positive control. The toxicity test showed that the test substance was not toxic to the inoculum. The validation criteria were met. Under the chosen conditions, 13% of the test substance was degraded within 28 days.