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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:
2011
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)
Deviations:
yes
Remarks:
1: Dissolved Organic Carbon of Ultra Pure Water is no more controlled, in connection with the DOC control data base. 2: The study plan was signed on 21/11/11 when experimentation already began on 14/11/11. These deviations have no effect on the validity
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
The inoculum came from the activated sludge of the biological wastewater treatment plant from Abidos (France, 64). The effluent, obtained 3 days before seeding the flasks, was centrifuged at approximately 20 °C for 10 min at 1000 g; the base was re-suspend ed in dilution water in order to keep the concentration unchanged with respect to the sample. The inoculum was preconditioned (aeration) until the flasks were inoculated. The amount of dry material in the inoculum, determined by desiccation at 105 °C until a constant weight is obtained, was 4.81 g/L.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
A known volume of inoculated dilution water, containing 100 mg/L of the test item is stirred darkness in a reactor at a constant temperature of 22°C and at pH 7.4.
The degradation is followed by the analysis of the carbon dioxide produced over a period of 28 days by measuring the quantity of oxygen generated automatically by the SELUTEC BSBdigi automatic respirometer: the CO2 generated by the ultimate biodegradation process is fixed by the soda lime placed in the reactor’s capsule. A drop in pressure ensues, which is detected by the manometer and sent to the control unit. In return, this sends an electrical current into the oxygen generator, which generates electrochemically an amount of oxygen in proportion to the intensity of the electrical current. 25 mg of test item are poured in test flasks, corresponding to a theoretical O2 mass of 53.79 mg per flask (ThOD 2.1515 mg O2/mg).

A parent solution of sodium benzoate in the dilution water to 2.5 mg/mL, was used in a proportion of 10 mL for 250 mL of dilution water, i.e. 25 mg, corresponding to a theoretical O2 mass of 41.65 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 95.44 mg per flask.

The flasks were installed in the respirometer where the stirring system was started. After a waiting period of approximately 0.5 hour, which is necessary to reach the thermal equilibrium of the solutions at a temperature of 22 ± 1°C, the aerated inoculum, preconditioned if required, is added to all the flasks that are then plugged.
Reference substance:
benzoic acid, sodium salt
Preliminary study:
No preliminary study
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Results with reference substance:
The percentage degradation of the reference item reached a level of 90% by 14 days (97.5% at day 28)

The calculated theoretical oxygen demand of COPPER DIBUTYLDITHIO CARBAMATE is 2.1515 mg O2/mg, based on the raw formula of the test item. This theoretical oxygen demand is calculated by assuming formation of ammonium, water and carbon dioxide (no nitrification was observed). The theoretical oxygen demand of sodium benzoate is 1.67 mg O2/mg. The pH value in the test suspension was 7.57 at day 28 which is in the range of 6-8.5. The maximum degradation level of COPPER DIBUTYLDITHIO CARBAMATE was 0% in 28 days. As no biodegradation was observed, the latency phase was not determined. COPPER DIBUTYLDITHIO CARBAMATE did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is already 38.5%, higher than 25% after 14 days.

Validity criteria fulfilled:
yes
Remarks:
see conclusions
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The method was applied with respect to the following criteria:

• The percentage degradation of the reference item reached a level of 90 % by 14 days which is above the requested level of 60 %;
• The oxygen uptake of the inoculum blank was of about 12 mg O2/L in 28 days, which is below 60 mg O2/L;
• The pH value in the test suspension was 7.57 at day 28 which is in the range of 6-8.5;
• In the toxicity control flasks, containing both the reference item and test item the percentage biodegradation reached 38.5% after 14 days. Since this value is higher than 25%, the test item is not inhibitory for inoculum.
Executive summary:

The ready biodegradability of COPPER DIBUTYLDITHIO CARBAMATE was evaluated in a study performed in accordance with OECD testing guideline 301 F and GLP requirements.

 

The maximum level of biodegradation was 0% in 28 days. Therefore, according to these results, COPPER DIBUTYLDITHIO CARBAMATE is not considered as readily biodegradable.

 

In the test conditions, no inhibitory effect of COPPER DIBUTYLDITHIO CARBAMATE on the micro-organisms of the inoculum was observed.

 

The sterile control did not show abiotic degradation.

 

Validity criteria were fulfilled

Description of key information

The ready biodegradability of COPPER DIBUTYLDITHIO CARBAMATE was evaluated in a study performed in accordance with OECD testing guideline 301 F and GLP requirements. According to the results, COPPER DIBUTYLDITHIO CARBAMATE is not considered as readily biodegradable as no biodegradation was observed.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The ready biodegradability of COPPER DIBUTYLDITHIO CARBAMATE was evaluated in a study performed in accordance with OECD testing guideline 301 F and GLP requirements.

 

The maximum level of biodegradation was 0% in 28 days. Therefore, according to these results, COPPER DIBUTYLDITHIO CARBAMATE is not considered as readily biodegradable.

In the test conditions, no inhibitory effect of COPPER DIBUTYLDITHIO CARBAMATE on the micro-organisms of the inoculum was observed.