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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:
From Mar. 20, 1990 to May 18, 1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
yes
Remarks:
The volume of test solution was reduced to 1.5 L. The CO2 was absorbed with NaOH and determined on a carbon analyzer. An emulsifier was used to achieve a better distribution in the medium. Only 1 reference used to confirm the degradation capability.
GLP compliance:
no
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): sewage treatment plant of CH-4153 Reinach
The preparation was carried out acocrding to the method described in the guideline.
Duration of test (contact time):
28 d
Initial conc.:
11.1 mg/L
Based on:
test mat.
Initial conc.:
21.5 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONCENTRATIONS PREPARATION:
- 1200 mL of the mineral solution with the inoculum were aerated for 24 hours in the test vessel.
In 300 mL mineral solution, 15 mL Polyoxyethylene-Sorbitan-Monooleate (TWEEN 80, FLUKA 93781) (solution of 30 mg in 100 mL bidistilled water) and 16.6 rsp 32.2 mg of test substance were added and homogenized. This solution was given to the test vessel which was immediately connected to the CO2 traps.
- Theoritical carbon dioxide evolution: 11.1 mg/L = 46.49 mg CO2/1.5 L and 21.5 mg/L = 90.19 mg CO2/1.5L
(calculation based on the chenical formula)

TEST CONDITIONS
- Composition of medium: The test medium was prepared according to the method described in the guideline
- Solubilising agent (type and concentration if used): Polyoxyethylene-Sorbitan-Monooleate (Tween 80)
- Test temperature: 22 ± 2ºC
- Air: approximately 25 mL/min purified from carbon dioxide

TEST SYSTEM
- Culturing apparatus: 2 liter flasks (dark brown glass) equipped with gas inlet and magnetic stirrer.
- Number of culture flasks/concentration: 1

SAMPLING
- Sampling frequency: Determination of CO2 on days 2, 5, 9, 14, 19, 23, 27 and 28.
- Determination of the initial CO2 of the 0.05N sodium hydroxide and the CO2 absorbed in the absorbers filled with 200 mL 0.05N sodium hydroxide

CONTROL AND BLANK SYSTEM
- Inoculum blank: water as specified in the guideline containing 15 mL of the Polyoxyethylene-Sorbitan-Monooleate (Tween 80, FLUKA 93781) solution
- Reference substance: 20 mg aniline/L
Reference substance:
aniline
Remarks:
Merck No. 1261 (Stability 06/90)
Parameter:
% degradation (CO2 evolution)
Value:
73
Sampling time:
28 d
Remarks on result:
other: 11.1 mg test substance / L
Parameter:
% degradation (CO2 evolution)
Value:
80
Sampling time:
28 d
Remarks on result:
other: 21.5 mg test substance / L
Results with reference substance:
98% biodegradability within 28 days
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Under the conditions of the study the biodegradation of the test material was determined to be 80% within 28 days. This reult meets the OECD 301 criteria for substances to be considered as "readily biodegradable".
Executive summary:

In this guideline (EU C.4-C) study, the biodegradation of the test material (EC 213-426-9) was determined to be 80% within 28 days. The test was conducted using an aerobic activated sewerage sludge taken from a municipal sewerage treatment plant. Based upon the result of the study, the test material should be considered under the criteria of the OECD 301 guideline.

Description of key information

Study conducted to recognised testing guideline.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In 1990 Ciba-Geigy Ltd. conducted a ready biodegradability test of the test substance according to EU C.4 (Carbon dioxide evolution test) guidelines under GLP regulations. The degradation degree reached 80% at 28 day, therefore, the test substance is readily biodegradable according to OECD 301 criteria.