3,7-dimethyloctan-3-yl acetate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July - December 2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

No CoA included in report, but molecular formula & weight were provided by the study sponsor. Not all validity criteria discussed and volatility of test substance not shown/given to conclude on test system suitability.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: Aerobic activated sludge from a waste water treatment plant ARA Ergolz II, Fullinsdorf, Switzerland treating predominantly domestic sewage.
- Preparation of inoculum for exposure: The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed thereafter dried and the ration of wet to dry weight was calculated. Calculated amounts of wet sludge were suspended in the test water to obtain a concentration equivalent to 4 g (10%) dry material per liter. During the holding, the sludge was aered at room temperature until use. Prior to use, the sludge was aerated at room temperature until use. Prior to use, the sludge was first thoroughly mixed and then diluted with test water at a concentration of 1 g per liter (dry weight basis).
- Concentration of sludge: Based on the determined dry weight of this diluted activated sludge defined amounts were added to test water to obtain a final concetration of 30 mg dry material per liter.

Duration of test (contact time):

28 d

Initial conc.:

101 mg/L

Based on:

test mat.

Initial conc.:

274 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Test water was prepared according to the test guidelines.
- Test temperature: 22 °C
- pH: t=0 7.4; t =28 d 7.4 - 7.7
- pH adjusted: yes, to obtain the final test water the pH was adjusted from 7.8 to 7.4 with diluted hrdochloric acid solution.
- Aeration of dilution water: The sludge was aered at room temperature prior to use. Aeration of dilution water not specified.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 mL Erlenmeyer flasks. The test flasks were incubated under continuous stirring in a SAPROMAT D12 (voith GmbH, Heidenheim, Germany).
- Number of culture flasks/concentration: 2
- Measuring equipment: Electrode type manometer
- Details of trap for CO2 and volatile organics if used: The CO2 is absorbed by soda lime and the total pressure drop is detected and converted into an electrical signal by means of an electrode type manometer. The consumed oxygen is replaced by electrolytically generated oxygen froma copper sulfate solution.

SAMPLING
- Sampling frequency: Oxygen consumption was recorded manually by taking a daily reading at least on each working day.
- Sampling method: manually

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes, with reference item sodium benzoate
- other: procedure control

Reference substance:

benzoic acid, sodium salt

Test performance:

Biodegradation in the toxicity control: The percent biodegradation in the toxicity control, containing both the test item and the reference item, was calculted based on the sum of the ThoD of the test item and the reference item. In the toxicity control, the course of biodegradation over the 28-day exposure period was similar to the two procedure controls, containing only the reference item. Within 14 days of exposure, biodegradation amounted to 35% based on the ThoD.

Thus according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L because biodegradation in the toxicity control was > 25% within 14 days.

Abiotic control: No degradation of the test item occured in the abiotic control under the test conditions within 28 days.

Key result

Parameter:

% degradation (O2 consumption)

Value:

55

Sampling time:

28 d

Details on results:

The percent biodegradation of the test item was calculated based on the theoretical oxygen demand of 2.72 mg/ O2/mg test item.

The biochemical oxygen demand of the test item in the test media significantly increased from exposure day 5 until test termination after 28 days. At the end of the 28-day exposure period, the mean biodegradation of the test item amounted to 55%. Consequently the test item was found to be biodegradable under the test conditions within 28 days. However the pass level for ready biodegradabiliy, i.e. biodegradation of at least 60% of the ThoD in a 10-day window within the 28-day period of the test, was not reached.

Results with reference substance:

Biodegradation of the reference item: The percent biodegradation of the reference item sodium benzoate was calculated based on the theoretical oxygen demand of 1.67 O2/mg. In the procedure controls, the reference item was degraded by an average of 88% by exposure day 14, thus confirming suitability of the activated sludge. At the end of the test (day 28), the reference item was degraded by an average of 91%.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Under the conditions of the test, the substance was biodegradable (55% within 28-days) however did not meet the pass level in 28 days or in the 10 day window .

Executive summary:

A manometric respiratory test was performed according to OECD TG 301F and in compliance with GLP. The oxygen consumption was followed for 28-days in an aerobic system inoculated with domestic activated sludge. 101.0 mg/L test substance (274 mg/L ThOD) was added to the test system. The experiment was performed in duplicate and inoculum control, procedure control, abiotic control, and toxicity control were performed in parallel. Under the conditions of the test, the substance was biodegradable (55% within 28-days) however did not meet the pass level in 28 days or in the 10 day window

Description of key information

A Manometric respiratory test was performed according to OECD TG 301F (GLP, Reliability 1) GLP. The oxygen consumption was followed for 28-days in an aerobic system inoculated with domestic activated sludge. 101.0 mg/L test substance (274 mg/L ThOD) was added to the test system. The experiment was performed in duplicate and inoculum control, procedure control, abiotic control, and toxicity control were performed in parallel. After 28 days the mean biodegradation was 55%. This value is below the 60% pass level, but close to it (replicate-1 = 59%, replicate-2 = 51%). The 10-day window is not met, but the curve shape also shows that the substance biodegradation kinetic is close from this criteria: biodegradation starts day-5, and the biodegradations are at day-15 equal to 53 for replicate-1 and 48% for replicate-2. The substance can therefore be considered as inherently (primary) biodegradable. Moreover, in environmental conditions, it can be expected that the substance will biodegraded with a rate equal or above 0.1 h-1. Therefore the substance is concluded as “inherently biodegradable, fulfilling specific criteria”.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, fulfilling specific criteria

Additional information

[Type of water: freshwater]