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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:
2017-09-26 to 2017-12-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Preparation of inoculum for exposure: The inoculated test medium, consisting of the required volumes of mineral medium stock solutions, ultrapure water and inoculum, was prepared in a measuring flask.
- Pretreatment: The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration for 2 1/3 hours. Thereafter the sludge was homogenized with a blender. After sedimentation the supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air for 6 days. 15 mLIL were used to initiate inoculation.
- Initial cell/biomass concentration: Approx. 1E+7 to 1E+8 CFU/L
Duration of test (contact time):
28 d
Initial conc.:
51 mg/L
Based on:
test mat.
Remarks:
corresponding to an oxygen demand of 56.6 mg O2/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F
- Test temperature: Nominal: 20 - 24 ± 1 °C; Actual: 20.0 - 20.2 °C. Occasionally below 20 °C (19.9 °C) for short periods.
- pH: 7.34 to 7.9
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus:Brown glass bottles (volume 500 mL)
- Number of culture flasks/concentration: 2 for inoculum control and treatment group, 1 for the toxicity control and the functional control
- Measuring equipment: The oxygen consumption was determined in the incubation vessels by the OxiTop® measuring system at 360 measuring points (every 112 minutes) during the 28 d incubation period. OxiTop@ OC110 controller with software Achat OC, WTW OxiTop® measuring heads, WTW
- Details of trap for CO2 and volatile organics if used: A rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2. The bottles were closed with OxiTop® measuring heads and the measuring system was activated.

SAMPLING
- Sampling frequency: at 360 measuring points (every 112 minutes) during the 28 d incubation period.
- Sampling method: in the incubation vessels by the OxiTop® measuring system

CONTROL AND BLANK SYSTEM
- Inoculum blank: The inoculated test medium, consisting of the required volumes of mineral medium stock solutions, ultrapure water and inoculum, was prepared in a measuring flask. 250 mL of this solution were filled in the brown glass bottles of the inoculum control, using a 250 mL measuring flask.
- Abiotic sterile control: The reference item was weighed out and transferred into a measuring flask, the required volumes of mineral medium stock solutions, ultrapure water and inoculum, were added. 250 mL of this solution were filled in the brown glass bottle of the functional control, using a 250 mL measuring flask.
- Toxicity control: The test item was weighed out and directly transferred into the test vessel with 250 mL of the reference item medium, using a 250 mL measuring flask.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
81
Sampling time:
28 d
Details on results:
The biodegradation of the test item in comparison to the readily degradable functional control and the toxicity control was presented. Both test item
replicates reached the 10% level (beginning of biodegradation) on day 3 and the mean of replicates reached the 60% pass level on day 15. The mean biodegradation on day 28 was 81%. The biodegradation was calculated with the ThODNO3 of 105 mg O2/L (i.e. with nitrification) was considered, since the concentration of nitrate increased during the test.
Results with reference substance:
The reference item sodium-benzoate reached 68% Biodegradation within three days and 98% Biodegradation within 28 days.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
In the present test conducted according to OECD guideline 301F (1992) activated, non-adapted sludge from a sewage treatment plant was incubated with 51 mg/L of Tetrahydrofolic acid (nominal). Biodegradation of the test item reached the 10% level after 3 days and the 60% pass level after 15 days. At day 28 the biodegradation of the test item was 81%. The validity criteria were fulfiled and thus, the test item is classified as readily biodegradable within the 28 day period of the study, but failing the 10-day-window according to Regulation (EC) No 1272/2008 (CLP) and the Globally Harmonized System for Classification and Labelling of Chemicals (GHS).

Description of key information

- study conducted according to OECD guideline 301F (1992) activated, non-adapted sludge incubated with 51 mg/L Tetrahydrofolic acid (nominal), the 10% biodegradation level was reached after 3 days and the 60% biodegradation pass level was reached after 15 days, at the end of the experimental time (28 days) biodegradation was 81%.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

In the present test conducted according to OECD guideline 301F (1992) activated, non-adapted sludge from a sewage treatment plant was incubated with 51 mg/L of Tetrahydrofolic acid (nominal). Biodegradation of the test item reached 10% level after 3 days and the 60% pass level after 15 days. At day 28 the biodegradation of the test item was 81%. The validity criteria were fulfiled and thus, the test item is classified as readily biodegradable within the 28 day period of the study, but failing the 10-day-window according to Regulation (EC) No 1272/2008 (CLP) and the Globally Harmonized System for Classification and Labelling of Chemicals (GHS).

[Type of water: freshwater]