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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:
2014-09-30 to 2014-10-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP Guideline Study
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Aeration stage of Severn Trent Water Plc sewage treatment plant, Loughborough, Leicestershire, UK on 29-09-2014
- Storage conditions: Washed twice by settlement and resuspension in mineral medium, maintained on continuous aeration at 21°C.
- Storage length: Used on day of collection
- Preparation of inoculum for exposure: As above
- Pretreatment: None
- Concentration of sludge: 30 mg suspended solids/L
- Initial cell/biomass concentration: Suspended solids concentration = 3.0 g/L prior to use
- Water filtered: no
Duration of test (contact time):
28 d
Initial conc.:
12.4 mg/L
Based on:
test mat.
Initial conc.:
10 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: as per OECD Guideline
- Additional substrate: No
- Solubilising agent (type and concentration if used): dispersed in mineral medium
- Test temperature: 20- 22°C
- pH: 7.4 - 7.8
- pH adjusted: yes to pH 7.4 prior to inoculm inclusion if needed.
- Suspended solids concentration: 30 mg ss/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5L test culture vessels
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: CO2 free air bubbled through solution at rate of 30 to 100 mL/min per vessel
- Measuring equipment: See analytical method
- Details of trap for CO2 and volatile organics if used: two 500 mL Dreschel bottles containing 350 mL of 0.05M NaOH, prepared using purified de-gassed water

SAMPLING
- Sampling frequency:
Ist absorber: Days 0, 2, 4, 6, 8, 10, 14, 21, 28 and 29
2nd absorber: Days 0 and 29
- Sample storage before analysis: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated mineral medim (x2)
- Abiotic sterile control: No
- Toxicity control: test item plus reference item in incoculated medium to give concentration of 20 mg C/L (x1)
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
11
Sampling time:
2 d
Parameter:
% degradation (CO2 evolution)
Value:
11
Sampling time:
10 d
Parameter:
% degradation (CO2 evolution)
Value:
13
Sampling time:
14 d
Parameter:
% degradation (CO2 evolution)
Value:
9
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
16
Sampling time:
29 d
Remarks on result:
other: Corrected to include carry-over of CO2 detected in absorber 2
Details on results:
The results of the inorganic carbon analysis of samples from the first absorber vessels on Day 29 showed an increase in all replicate vessels with the exception of inoculum control vessel R2. This decrease was considered to be sue to sampling/analytical variation. Inorganic carbon analysis of the samples from the second absorber vessesl on Day 29 conformed that no significant carry-over of CO2 into the second absorber vessels occurred.
The test item attained 16% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and condtions of OECD Guideline No. 301B.
The toxicity control attained 55% biodegradation after 14 days and 48% biodegradation after 28 days thereby confirming that the test item did not exhibit an inhibitory effect on the sewage treatment micro-organisms used in the test. The slight decrease in biodegradation between days 14 and 28 was considered to be due to sampling/analytical variation.
Results with reference substance:
Sodium benzoate attained 83% biodegradation after 14 days and 88% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test item attained 16% degradation after 28 days. The test item cannot therefore be considered to be readily biodegradable under the terms and conditions of the Guideline.
Executive summary:

Test Guidance

OECD Guideline 301B, EC Method C.4 -C and US EPA OPPTS 835.3110

Method

The test item at a concentration of 10 mg C/L was exposed to activated sewage sludge micro-organisms with a mineral medium in sealed culture vessels in the dark at 20 to 22°C for 28 days.

The degradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

Results

The test item attained 16% degradation after 28 days.

Conclusions

The test item cannot therefore be considered to be readily biodegradable under the terms and conditions of the Guideline.

Description of key information

The test item attained 16% degradation after 28 days. The test item cannot therefore be considered to be readily biodegradable under the terms and conditions of the Guideline.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

In a key study performed to OECD Guideline 301B, EC Method C.4 -C and US EPA OPPTS 835.3110, the test item at a concentration of 10 mg C/L was exposed to activated sewage sludge micro-organisms with a mineral medium in sealed culture vessels in the dark at 20 to 22°C for 28 days.

The degradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

The test item attained 16% degradation after 28 days. The test item cannot therefore be considered to be readily biodegradable under the terms and conditions of the Guideline.