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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2008-03-11 to 2008-08-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- aspect: solid, white
- synonym: Montanov 202 (APG C20-C22)
- CAS N°: icosyl D-glucoside 100231-68-3/fatty alcohol chain C20-C22 90604-34-5
- batch number: T71225
- expiry date: 2009-03-21 (re-test date)
- stability: in water test item is considered to be stable under test conditions
-storage: at room temperature, at below 40°C, in the dark

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Aerobic activated sludge, micro organisms from a domestic waste water treatment plant was supplied by the sewage plant Darmstadt, Germany.
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 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. This suspension was used for the experiment.
Duration of test (contact time):
ca. 28 d
Initial test substance concentration
Initial conc.:
ca. 102 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The test product and reference product were directly weighed into the test flasks. No emulsifiers or solvents were used, but the solutions were dispersed by stirring to achieve a homogeneous solution of the test substance.
The closed test flasks were incubated in a climatised room (22°C) under continuous stirring for 28 days.
2 flasks were tested for the test product.
2 flasks were tested for the inoculum control.
1 flask was tested for the reference item (sodium benzoate)

Results and discussion

Test performance:
inoculum control: the oxygen demand of the inoculum control (medium and inoculum) was 25 mg O2/L and thus not greater than 60 mg/L within 28 days as required by the test guideline.
pH value: The pH-value of the test product flasks at the end of the test was within the range of pH 6.0 to 8.5 as required by the test guideline.
Reference item: The reference product sodium benzoate was degraded to more than 60% after 3 days of incubation.
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
ca. 67
St. dev.:
0
Sampling time:
28 d
Remarks on result:
other: Test conditions: 22°C; darkness
Details on results:
The biodegration did not reach the pass criterion of 60% degradation within the 10 day-window.
At the end of the experiment, the difference in replicate variation was 0%.

BOD5 / COD results

Results with reference substance:
sodium benzoate was degraded to more than 60% after 3 days of incubation.

Applicant's summary and conclusion

Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
The degradation rate of the test substance did not reach 60% within the 10 day-window. The test product contains no nitrogen, therefore no nitrification was expected.
According to the test guideline, the test substance is considered to be readily biodegradable, but failing the 10-day window.
Executive summary:

The test substance was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days. The biodegradation was followed by the oxygen uptake the micro-organisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

Degradation rate of test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

The test product contains no nitrogen, therefore the evaluation of biodegradation has to be based on ThOD NH4. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the 10 day-window, describing the period between reaching at least 10% degradation and 60% degradation. This period should not exceed 10 days.

The mean biodegradation after 28 days of the test product was 67% (ThOD NH4); the 10 day-window criterion was failed.

Therefore, the test product is considered to be readily biodegradable, but failing the 10 day window.

The reference item sodium benzoate was sufficiently degraded to a mean of 104% after 14 days and to a mean of 110% after 28 days of incubation, thus confirming the suitability of the aerobic sludge inoculum used.