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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:
October 06 to November 26, 2009
Reliability:
1 (reliable without restriction)
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
The inoculum was prepared in the laboratory from secondary effluent from a wastewater treatment plant with activated sludge treating the domestic wastewater in the municipality of Abidos (France, 64). The inoculum used provides bacteria at concentration levels usually situated between 107 and 108 cells per litre. The inoculum concentration in the test medium was equivalent to a maximum level of 30 mg suspended matter. The inoculum has been pre-conditioned by aerating the secondary effluent, without other treatment or addition, for two days at the test temperature.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
A 0.6 g/L solution of DIMETHYLETHYLAMINE in the dilution water was prepared and used in a proportion of 1 mL per flask, i.e. 0.6 mg, corresponding to a theoretical O2 mass of 1.578 mg per flask (ThOD 2.63 mg O2/mg).
Sodium benzoate (108 mg) was dissolved in 100 mL of mineral medium. One mL per BOD Bottle was used to give 1.08 mg per flask, which corresponds to a theoretical O2 mass of 1.804 mg per flask (ThOD 1.67 mg O2/mg).
In the inhibition monitoring flask, equivalent quantities of test and reference items are introduced. For this flask, the corresponding theoretical mass of O2 is 1.691 mg per flask.
The test solutions were inoculated with micro-organisms from a heterogeneous population, and stored in closed, completely full bottles, away from light and at a constant temperature (20°C +/- 1°C).
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
67
Sampling time:
28 d
Details on results:
The calculated theoretical oxygen demand of DIMETHYLETHYLAMINE is 2.63 mg O2/mg. This theoretical oxygen demand is calculated by assuming formation of ammonium, water and carbon dioxide. The theoretical oxygen demand of sodium benzoate is 1.67 mg O2/mg. The maximum ultimate biodegradation level of DIMETHYLETHYLAMINE was 67% after 28 days. This level was reached within a 10 days window.
Results with reference substance:
DIMETHYLETHYLAMINE did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is already 54 %, higher than 25 % after 14 days.

The percentage of degradation of the reference item reached only a level of 31 % by 14 days which is below the requested level of 60 %. This can probably be explained by a inoculum activity which is not optimum. Nevertheless this does not invalidate the final result of the study. One can just expect that with a higher inoculum activity, DIMETHYLETHYLAMINE biodegradation would have been faster.
Validity criteria fulfilled:
no
Remarks:
The percentage of degradation of the reference item reached only a level of 31 % by 14 days which is below the requested level of 60 %. Nevertheless this does not invalidate the final result of the study.
Interpretation of results:
readily biodegradable
Conclusions:
The study of the "ready" aerobic biodegradability of DIMETHYLETHYLAMINE using the OECD method 301 D shows that this item reached a maximum biodegradation level of 67 % in 28 days. DIMETHYLETHYLAMINE is therefore considered readily biodegradable.
Executive summary:

The study of the "ready" aerobic biodegradability of DIMETHYLETHYLAMINE using the OECD method 301 D shows that this item reached a maximum biodegradation level of 67 % in 28 days. The item did not demonstrate any inhibiting effect on the micro-organisms. According to OECD Guideline 301 D, a substance is considered to be readily biodegradable if a level of 60 % degradation is reached within the 10-day period following the beginning of the degradation phase (which starts when 10 % of the TOC has been biodegraded). This 60 % must be reached during the 28-day test period. Under the test conditions, the percentage of biodegradation of DIMETHYLETHYLAMINE reached 67 % of the ThOD at the end of the test (28 days) and this level was obtained within a 10 days window.Based on these criteria, DIMETHYLETHYLAMINE is readily biodegradable.

Note: the percentage of degradation of the reference item reached only a level of 31 % by 14 days which is below the requested level of 60 %. This can probably be explained by a inoculum activity which is not optimum. Nevertheless this does not invalidate the final result of the study. One can just expect that with a higher inoculum activity,DIMETHYLETHYLAMINEbiodegradation would have been faster.

Description of key information

The study of the "ready" aerobic biodegradability of dimethylethylamine using the OECD method 301 D shows that this item reached a maximum biodegradation level of 67 % in 28 days. The item did not demonstrate any inhibiting effect on the micro-organisms. According to OECD Guideline 301 D, a substance is considered to be readily biodegradable if a level of 60 % degradation is reached within the 10-day period following the beginning of the degradation phase (which starts when 10 % of the TOC has been biodegraded). This 60 % must be reached during the 28-day test period. Under the test conditions, the percentage of biodegradation of dimethylethylamine reached 67 % of the ThOD at the end of the test (28 days) and this level was obtained within a 10 days window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information