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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:
24-04-2013 to 23-05-2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: according to the guideline, under GLP
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Principles of method if other than guideline:
The test substance was prepared by High Shear Mixing (7500 rpm for 15 minutes)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Severn Trent Water Plc sewage treatment plant Loughborough, Leicesterhire, UK
- Storage conditions: under aeration at 21 °C
- Storage length: <1 day
- Preparation of inoculum for exposure: washed twice by settlement and resuspended thereafter
- Pretreatment: none
- Concentration of sludge: suspended solids 3.1 g/L
Duration of test (contact time):
29 d
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Solubilising agent (type and concentration if used): none
- Test temperature: 21 °C
- pH: 7.2-7.6 (at day 0 after adjustment and day 28)
- pH adjusted: yes in all vessels
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks: 2 test substance +inoculum, 2 inoculum, 2 reference substance + inoculum, 1 toxicity control
- Method used to create aerobic conditions: bubbling of CO2-free air at 30-100 mL/min
- Details of trap for CO2 and volatile organics: 2 NaOH CO2-traps (Drechsel)

SAMPLING
- Sampling frequency:
CO2 on day 0, 2, 6, 8, 10, 14, 21, 28, 29 (second trap on day 0 and 29) analyses in triplicate
IC: on day 0 (stated to be not possible bacause of insolubility of the test item, but measurements included show accuracy within 5% of TC)
- Sterility check if applicable: not included
- Sample storage before analysis: none

CONTROL AND BLANK SYSTEM
- Inoculum blank: in duplicate
- Abiotic sterile control: not included
- Toxicity control: single vessel with test substance + reference substance + inoculum (20 mg C/L)

STATISTICS
student's t-test
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
0 d
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
29 d
Remarks on result:
other: after acidification of the medium
Details on results:
Test solutions all were pale brown dispersions. No undissolved test substance was visible.
Results with reference substance:
Degradation 62% on day 29
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance attained 0 % degradation after 29 days and is therefore considered not readily biodegradable.
Executive summary:

The test substance was tested in a CO2 evolution test for 29 days. The test substance attained 0% degradation and is therefore considered not readily biodegradable.

Description of key information

The test substance was tested in a CO2 evolution test for 29 days. The test substance attained 0% degradation and is therefore considered not readily biodegradable (Harlan 2013).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information