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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP guideline study. K2 score due to read-across.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
For technical reasons the pH-value was not measured at the end of test of the abiotic conrol and toxicity control. There is no effect on the study.
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
yes
Remarks:
For technical reasons the pH-value was not measured at the end of test of the abiotic conrol and toxicity control. There is no effect on the study.
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Sewage plant Darmstadt, Germany
- Conditioning: The aerobic activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and centrifuged again. This procedure was done three times. The sediment was re-suspended in test water and aerated overnight. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 1.5 g dry material per litre were mixed with test water.
- Concentration of sludge: 1.5 g dry sludge per litre test water.
- Water filtered: no
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
105 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Sewage sludge
- Additional substrate: none
- Solubilising agent (type and concentration if used): not used
- Test temperature: 21 - 22 °C
- pH: 7.6 at the start of the test; 7.9 at the end of the test.
- Aeration of dilution water: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: The test flasks.
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: ambient air
- Measuring equipment: BSB Sensomat system, Aqualytic Dortmund
- Test performed in closed vessels due to significant volatility of test substance: closed vessels
- Details of trap for CO2 and volatile organics if used: The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide.
- Other: The closed test flasks were incubated in a climatised room under continuous stirring.

SAMPLING
- Sampling frequency: day 0 and day 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (aliquote of the sewage sludge used in the test)
- Abiotic sterile control: yes
- Toxicity control: Sodium Benzoate

STATISTICAL METHODS: Not applicable
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
Not performed due to the chemical nature of the test substance.
Test performance:
Validitiy criteria were applied in the study and showed the following results.

Inoculum Control: The oxygen demand of the inoculum control (medium and inoculum) was 27.5 mg O2/L and thus not greater than 60 mg O2/L within 28 days as required by the test guideline.

pH-Value: The pH-value of the test item flasks at the end of the test was between 7.0 – 7.1 and therefore within the range of pH 6.0 to 8.5 as required by the test guideline.

Reference Item: The percentage degradation of the reference item should reach the level for ready biodegradability (>60%) within 14 days as required by the test guideline. The reference item sodium benzoate was degraded to more than 60% after 4 days of incubation.

Test Item: The difference of duplicate values for the degradation of the test item at the plateau, at the end of the test and at the end of the 10-day window was less than 20%. The difference on day 28 was 1.9%. The validity criterion was fulfilled.
% Degradationopen allclose all
Parameter:
other: ThOD-NH4
Value:
108
Sampling time:
28 d
Parameter:
other: ThOD-NO3
Value:
82
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
The reference item sodium benzoate was sufficiently degraded to 80% after 14 days and to 83% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
In a GLP guideline study according to OECD 301 F L-valine showed to be readily biodegradable.