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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:
01.02.-04.03.2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
INOCULUMThe inoculum contained a mixed population of microorganisms obtained from the secondary effluent of the waste water treatment plant of Pardubice processing predominantly municipal sewage.PREPARATION INOCULUMThe fresh collected waste water was filtered through paper filter. COD was determined and waste water was aerated till using.Justification of the test systemThe inoculum preparation is in conformity with the recommendations of the test guideline.
Duration of test (contact time):
28 d
Initial conc.:
3.4 mg/L
Based on:
COD
Details on study design:
The mineral medium was strongly aerated for 20 minute and let standing for 20 hours at the test temperature. The volume of waste water for the inoculation of mineral medium was chosen 2.0 mL per 1 L of medium (COD of waste water: 73 mg.L-1).30 L aerated mineral medium was prepared for the test and before the beginning of the test it was inoculated with 60 mL of modified waste water.- pH: 7.4-Temperature: 20 ± 1.0 °C-Illumination: no illumination, in the dark-Exposition time: 28 daysTEST SYSTEM-2 x 9 bottles with test substance and inoculated medium-2 x 9 bottles with reference substance and inoculated medium for the check of inoculum activity-9 bottles with test substance and inoculated medium for the determination of oxidized nitrogen forms-2 x 5 bottles with test and reference substance mixture and inoculated medium for the toxicity test-2 x 9 bottles with inoculated medium only for the blank determinationCONTROL AND BLANK SYSTEM- Inoculum blank: yes, the inoculated mineral medium- Toxicity control: yes, the test substance and refence substance mixturedMEASUREMENTAt the 3rd, 7th, 10th, 14th, 17th, 21st, 24th and 28th day of test the appropriate bottles from each serieswere taken off and they were analysed for dissolved oxygen.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
13.5
Sampling time:
28 d
Key result
Parameter:
COD
Value:
0.701 other: mg.mg-1
Key result
Parameter:
BOD5
Value:
0.02 other: mg.mg-1
Results with reference substance:
COD of the reference substance: 1.633 mg.mg-1,
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
In this 28-day study of ready biological degradability the degradation of 13.5 % of the test substance, Direct Blue 78, was attained in the end of study.
Executive summary:

The test substance, Direct Blue 78, was tested for the ready biological degradability in Closed Bottle Test.

 

Test performance

The test was performed according to:

Method C.4E - Closed Bottle Test, Council Regulation (EC) No. 440/2008, published in O.J.L 142, 2008.

 

The results of biological degradation are related to experimentally determined COD values of the test and reference substance at the beginning of the test.

The test substance was sufficiently soluble in used mineral medium so the dosage from the stock solution was carried out.

Sodium benzoate was used as the reference substance. The dosage was carried out from the stock solution.

COD of the test substance in medium at the beginning of the main test:             3.40 mg·L-1

COD of the reference substance in medium at the beginning of the main test:     3.43 mg·L-1

In parallel to the main test the toxicity test was performed.

Based on the test substance contains nitrogen in the chemical composition, the oxidized nitrogen forms were determined and the correction for nitrification was carried out.

The test was performed at temperature of 20 ± 1 °C with the pH values of solutions 7 - 8 at the beginning of the test.

 

Validity of the test

The prescribed validity criteria in the test were fulfilled.

The test substance was not inhibiting for the used inoculum.

Since all criteria of acceptability were met, this study is considered to be valid.

 

Test results

In this 28-day study of ready biological degradability the degradation of 13.5 % of the test substance, Direct Blue 78, was attained in the end of study.

Description of key information

The test was performed according to:

Method C.4E - Closed Bottle Test, Council Regulation (EC) No. 440/2008, published in O.J.L 142, 2008.

Only one study is available.

GLP study.

Klimish score 1.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information