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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:
May to June 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted according to OECD Guideline and under GLP conditions.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Preparation of inoculum for exposure: The activated sewage sludge sample was washed two times by settlement and resuspension in mineral medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. The washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC and used on the day of collection.
- Water filtered: yes
- Type and size of filter used, if any: GF/A filter paper using a Buchner funnel

No additional data
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
other: carbon
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Solution a KH2PO4 8.50 g/L, K2HPO4 21.75 g/L, Na2HPO4.2H2O 33.40 g/L, NH4Cl 0.50 g/L
Solution b CaCl2 27.50 g/L
Solution c MgSO4.7H2O 22.50 g/L
Solution d FeCl3.6H2O 0.25 g/L
To 1 liter (final volume) of purified water was added the following volumes of solutions a – d.
10 mL of Solution a
1 mL of Solution b
1 mL of Solution c
1 mL of Solution d
- Test temperature: approximately 21 ºC
- pH: 7.4 ± 0.2
- pH adjusted: yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 liter test culture vessels
- Method used to create aerobic conditions: The CO2-free air was produced by passing compressed air through a glass column containing self-indicating soda lime (Carbosorb®) granules.

SAMPLING
- Sampling frequency: Samples (2 mL) were taken from the first CO2 absorber vessels on Days 0, 2, 6, 8, 14, 17, 21, 28 and 29. The second absorber vessels were all sampled on Days 0 and 29.

CONTROL AND BLANK SYSTEM
- Toxicity control: For the purposes of the test, a toxicity control, containing the test item and sodium benzoate, was prepared in order to assess any toxic effect of the test item on the sewage sludge microorganisms used in the test.

Reference substance:
benzoic acid, sodium salt
Preliminary study:
Not applicable.
Parameter:
% degradation (CO2 evolution)
Value:
26
Sampling time:
28 d
Details on results:
N-octadecylstearamide attained 26% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.
The toxicity control attained 58% degradation after 14 days and 90% degradation after 28 days thereby confirming that N-octadecylstearamide was not toxic to the sewage treatment micro-organisms used in the test.
Sodium benzoate attained 71% degradation after 14 days and 84% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Validity criteria fulfilled:
yes
Interpretation of results:
other: Not readily biodegradable
Conclusions:
The test material attained 26% degradation after 28 days and is not considered to be readily biodegradable under the conditions of OECD Guideline No. 301B.
Executive summary:

The test material attained 26% degradation after 28 days and is not considered to be readily biodegradable under the conditions of OECD Guideline No. 301B.

Description of key information

The test material attained 26% degradation after 28 days and is not considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria

Additional information