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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:
2016-06-20 to 2016-09-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Designation: Art. 808616
Synonym: Taurine
Appearance: white crystalline powder
Released until: Sep 30, 2020
ThOD: 0.77 mg O2/mg
ThOD with nitrification: 1.28 mg O2/mg
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Municipal sewage treatment plant, D-31137 Hildesheim

- Pretreatment:
The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was filled up with mineral salts medium and was maintained in an aerobic condition by aeration for 2-4 hours. Thereafter the sludge was homogenized with a blender. The supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air for 6 days. 10 mL/L were used to initiate inoculation.

- Concentration of sludge: 10 mL/L
- Initial cell/biomass concentration: 10^7 - 10^8 CFU/L
- Water: demineralized
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Initial conc.:
52.4 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Preparation of Test Flasks:
All test solutions were prepared in measuring flasks in demineralised water with the required amounts of mineral medium stock solutions and 10 mL/L inoculum. The test item was weighed out and demineralised water was added. After ultrasonic treatment it was transferred into the measuring flasks.

The reference item was weighed out and transferred into the measuring flasks with demineralised water.

250 mL measuring flasks were used to place 250 mL of the test solutions in the brown glass bottles.

A rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2. The bottles were closed with Oxi-Top® measuring heads and the measuring system was activated.


Measurements:
The temperature in the incubator was documented continuously throughout the test by a hygrothermograph.
At test start the pH-values of the test solutions in the measuring flasks (before dividing) and at test end the pH-values of the test solutions in the brown glass bottles were determined.
The oxygen consumption was determined continuously from the pressure in the incubation vessels by OxiTop® measuring system at 360 measuring points (every 112 minutes) during the 28 d incubation period.



Reference substance:
benzoic acid, sodium salt
Test performance:
Results of the Functional Control
The pass level for ready biodegradation (> 60% degradation) was reached on day 4. The validity criterion that the degradation should be > 60% after 14 d was fulfilled. Stages of Biodegradation: The adaptation phase changed to degradation phase within 1 day (degradation > 10%) and the biodegradation came to a maximum of 93% on day 24

Results of the Toxicity Control
In the toxicity control the biodegradation achieved 73% after 14 days. After 28 days the biodegradation came to 84%. The validity criterion that the test item should not inhibit the biodegradation of the reference item was fulfilled.
Key result
Parameter:
% degradation (O2 consumption)
Value:
70
Sampling time:
28 d
Details on results:
Both test item replicates reached the 10% level (beginning of biodegradation) on day 3. The course of the deg­ radation was rapid and the test item replicates reached the 60% pass level on day 17. The mean biodegradation on day 28 was 70%.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
The test item is classified as readily biodegradable within the 28 day period of the study, but without complying with the 10 day-window.
Executive summary:

The test item is classified as readily biodegradable within the 28 day period of the study, but without complying with the 10 day-window.

Description of key information

The test item is classified as readily biodegradable within the 28 day period of the study, but without complying with the 10 day-window.

Key value for chemical safety assessment

Additional information