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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:
2013-09-18 to 2013-12-16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
GLP study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
adopted 1992-07-17
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
TEST MATERIAL
- Lot/batch No.of test material: 12/NB/016
- Expiration date of the lot/batch: 2014-10-01
- Purity test date: 2013-10-01


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Tightly closed, protected from moisture at room temperature
- Stability under test conditions: stable
- Solubility and stability of the test substance in the solvent/vehicle:6.9 g/L (water solubility)

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal sewage treatment plant, 31137 Hildesheim, Germany
- Pretreatment:
The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration for 2 hours. Thereafter the sludge was homogenized with a blender. The supernatant was decanted and maintained in an aerobic condition by aeration with CO2 free air until test start. 10 mL/L of this mixture were used to initiate inoculation.

Duration of test (contact time):
28 d
Initial conc.:
16 mg/L
Based on:
test mat.
Remarks:
corresponding to a carbon content (TOC) of 10.6 mg C/L
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST METHOD
Duration: 28 d
Application: Once at test start
Test vessels: 5000 mL, brown glass
Volume of the test medium : 3000 mL
Test medium: Mineral salts medium acc. to OECD 301 B / CO2 Evolution Test
Test temperature: Nominal 22 ± 2 °C, actual measured 20- 23 °C
Dispersion treatment: Continuous stirring
Aeration: 30 - 100 mL/min
Photoperiod: Low light conditions (brown glass bottles)
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
16
Sampling time:
3 d
Parameter:
% degradation (CO2 evolution)
Value:
68
Sampling time:
10 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
96
Sampling time:
28 d
Details on results:
The biodegradation of the test item is shown graphically in Figure 1 in comparison to the readily degradable functional control and the toxicity control. The mean 10 % level (beginning of biodegradation) was reached on day 3. The 60 % pass level was reached within 10 days. The mean biodegradation after 28 days was 96 %.
Results with reference substance:

To check the activity of the test system, sodium benzoate was used as functional control. The percentage degradation of the functional control reached the pass level of 60 % within 6 days and a biodegradation of 85 % after 28 days. In the toxicity control containing both test and reference item a biodegradation of 25 % was reached after 5 days. After 15 days a biodegradation of 68 % was determined and it came to 84 % after 28 days. The biodegradation of the reference item was not inhibited by the test item in the toxicity control.

Biodegradation of the test item in comparison to the functional control and toxicity control:

  Biodegradation
            Study Day [d]
   15  21  28
 Test Item, 1st Replicate  35  78  87  95
 Test Item, 2nd Replicate 39   81  89  96
 Functional Control 61   82  84  85
 Toxicity Control  37  68  76  84
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Under the test conditions the test item is readily biodegradable within 28 days and complying to the 10-day-window.
Executive summary:

Under the test conditions the test item is readily biodegradable within 28 days and complying to the 10-day-window.

Description of key information

Based on the results of a CO2 evolution test (Modified Sturm Test) the test material is considered to be readily biodegradable within 28 days and complying to the 10-day window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information