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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:
26 August 1997 to 25 September 1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study performed in accordance to OECD test guideline.
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)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not relevant
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Severn Trent Water Plc sewage treatment plant, Belper, Derbyshire, UK.
- Storage conditions: 21 ºC, in darkness
- Preparation of inoculum for exposure: The sample of activated sewage sludge was maintained on continuous aeration upon receipt. A sample of the activated sewage sludge was washed three times by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon that may have been present. A sub-sample of the washed sewage sludge was then removed and the suspended solids concentration determined.
- Initial cell/biomass concentration: 10 mg carbon/L
- Water filtered: yes
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Solubilising agent (type and concentration if used): not necessary
- Test temperature: 21°C
- pH: not specifed
- Aeration of dilution water: not specified
- Suspended solids concentration: 30 mg/l
- Continuous darkness: yes



SAMPLING
- Sampling frequency: once on day 1,2,3,6,8,10,12,14,16,18,20, 22,24 27, 28, 29
- Sampling method: The CO2 produced by degradation was collected in two 500 ml Dreschel bottles containing 350 ml of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified de-gassed water.
- Sample storage before analysis: samples not analysed immediately were stored deep frozen at -20 ºC.
- Other: On day 28 1 ml of concentrated hydrochloric acid was added to each vessel to drive any inorganic carbonates formed. The vessels were resealed, aerated overnight and the final samples taken from both absorber vessels on day 29.




CONTROL AND BLANK SYSTEM
- Inoculum blank: Sodium benzoate attained 94% degredation after 28 days, confirming the suitability of the inoculum and test conditions
- Toxicity control: Attained 31% degradation after 14 days and 57% degradation after 28 days thereby confirming that the test material was not toxic to the sewage treatment micro-organisms use in the study at 10 mg C/L

Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
29
Sampling time:
28 d
Results with reference substance:
Sodium benzoate attained 94% degradation after 28 days, confirming the suitability of the inoculum and test conditions
Validity criteria fulfilled:
yes
Interpretation of results:
other: Not readily biodegradable; inherent biodegradability not assessed in this test.
Conclusions:
The test material attained 29% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B
Executive summary:

A study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the OECD Guidelines for Testing of Chemicals (1992) No 301 B, "Ready Biodegradability; CO2 Evolution Test" referenced as Method C.4-C of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

The test material was exposed to activated sewage sludge micro-organisms at a concentration of 10 mg C/L with culture medium in sealed culture vessels in the dark at 21°C for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

The test material attained 29% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301 B.

Description of key information

OECD test 301B: Modified Sturm Test - 29% degradation after 28 days therefore substance not considered readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

A study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the OECD Guidelines for Testing of Chemicals (1992) No 301 B, "Ready Biodegradability; CO2 Evolution Test" referenced as Method C.4-C of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

The test material was exposed to activated sewage sludge micro-organisms at a concentration of 10 mg C/L with culture medium in sealed culture vessels in the dark at 21°C for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

The test material attained 29% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301 B.