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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:
Experimental start: 07/04/11 - Experimental end: 05/05/11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, 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 2 days before seeding the flasks, was centrifuged at approximately 20 °C for 20 min at 4000 g; the base was re-suspended 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 6.84 g/L.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
N,N’-Diphenyl Thiourea has a low solubility, then 25 mg are weighted and introduce directly into the flasks, corresponding to a theoretical O2 mass of 56 mg per flask (ThOD 2.243 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 97.7 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 ± 2°C, the aerated inoculum, preconditioned if required, is added to all the flasks that are then plugged.
Reference substance:
benzoic acid, sodium salt
Remarks:
See "Any other information on materials and Methods incl. tables"
Preliminary study:
No preliminary study was performed.
Test performance:
Validity criteria were fulfilled. See "Remarks on Results incl. tables and figures"
Key result
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
28 d
Details on results:
The calculated theoretical oxygen demand of N,N’-Diphenyl Thiourea is 2.243 mg O2/mg. 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 maximum degradation level of N,N’-Diphenyl Thiourea was 0% in 28 days.
As no biodegradation was observed, the latency phase was not determined.
N,N’-Diphenyl Thiourea did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is already 38 %, higher than 25 % after 14 days.
Results with reference substance:
The percentage degradation of the reference item reached a level of 80 % by 14 days which is above the requested level of 60 %
Validity criteria fulfilled:
yes
Remarks:
See "Overall remarks"
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The purpose of this study was to assess the ready biodegradability of the test item according to the OECD guideline 301 F “Ready biodegradability: Manometric Respirometry Test”.
According to the OECD guideline 301, the pass level for ready biodegradability is 60 % of Theoretical Oxygen Demand (ThOD). This level has to be reached in a 10-d window within the 28-d period of the test. The 10-d window begins when the degree of biodegradation has reached 10 % of ThOD and must end before day 28 of the test.
Under the test conditions, the percentage of biodegradation of N,N’-Diphenyl Thiourea reached 0 %of the ThOD at the end of the test (28 days).
According to OECD guideline 301F, N,N’-Diphenyl Thioureais not readily biodegradable.
N,N’-Diphenyl Thiourea did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is 38% higher than 25 % within 14 days.
Executive summary:

The purpose of this study was to assess the ready biodegradability of the test item according to the OECD guideline 301 F “Ready biodegradability: Manometric Respirometry Test”.

According to the OECD guideline 301, the pass level for ready biodegradability is 60% of Theoretical Oxygen Demand (ThOD). This level has to be reached in a 10-d window within the 28-d period of the test. The 10-d window begins when the degree of biodegradation has reached 10% of ThOD and must end before day 28 of the test.

Under the test conditions, the percentage of biodegradation of N,N’-Diphenyl Thiourea reached 0%of the ThOD at the end of the test (28 days).

According to OECD guideline 301F, N,N’-Diphenyl Thiourea is not readily biodegradable.

N,N’-Diphenyl Thiourea did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is 38% higher than 25% within 14 days.

Description of key information

A study was performed according to the OECD guideline 301 F: 0 % biodegradation reached after 28d
N,N’-Diphenyl Thiourea is not readily biodegradable.
N,N’-Diphenyl Thiourea did not inhibit the micro-organisms.

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable
Type of water:
freshwater

Additional information

The purpose of this study was to assess the ready biodegradability of the test item according to the OECD guideline 301 F “Ready biodegradability: Manometric Respirometry Test”.

According to the OECD guideline 301, the pass level for ready biodegradability is 60% of Theoretical Oxygen Demand (ThOD). This level has to be reached in a 10-d window within the 28-d period of the test. The 10-d window begins when the degree of biodegradation has reached 10% of ThOD and must end before day 28 of the test.

Under the test conditions, the percentage of biodegradation of N,N’-Diphenyl Thiourea reached 0% of the ThOD at the end of the test (28 days).

According to OECD guideline 301F, N,N’-Diphenyl Thiourea is not readily biodegradable.

N,N’-Diphenyl Thiourea did not inhibit the micro-organisms as shown by the toxicity control flask where biodegradation percentage is 38% higher than 25% within 14 days.

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