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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted to generally accepted guidelines and in accordance with GLP
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
Room temperature dropped below 19.5oC, to as low as 18oC. This deviation is not considered to have had an advserse effect on study given that all validity criteria were met.
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
GLP compliance:
yes (incl. QA statement)
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 sewage treatment plant, Loughborough, UK
- Storage conditions: Continuous aeration at ambient laboratory temperature, approximately 21oC
- Storage length: Used on day of collection
- Preparation of inoculum for exposure: Seage sludge washed twice by settlement and resuspension in mineral medium. Washed sample maintained on continuous aeration at approximately 21oC.
- Concentration of sludge: Suspended solids concentration equal to 4.6 g/L

Duration of test (contact time):
ca. 56 d
Initial conc.:
ca. 12.7 mg/L
Based on:
ThOD/L
Details on study design:
TEST CONDITIONS
- Composition of medium: as recommended in OECD guidelines
- Test temperature: 22 +/-2oC
- pH: 7.5
- pH adjusted: Yes
- Aeration of dilution water: CO2-free air bubbled through solutions at 30-100 mL/min
- Suspended solids concentration: 30 mg/L (nominal)
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 5L culture vessels
- Number of culture flasks/concentration: Duplicate test vessels
- Method used to create aerobic conditions: CO2-free air bubbled through solutions at 30-100 mL/min
- Test performed in open system: No
- Details of trap for CO2 and volatile organics if used: Two 500 mL Dreschel bottles containing 0.05 M NaOH in purified water.

SAMPLING
- Sampling frequency: 0,2,6,8,10,14,21,28,35,42,49,56 and 57 days
- Sampling method: Samples taken from first CO2 absorber vessel. Absorber vessel 2 sampled days 0 and 57
- Sample storage before analysis: None

CONTROL AND BLANK SYSTEM
- Inoculum blank: Mineral medium only
- Procedure control: Sodium benzoate (17.1 mg/L), equivalent to 10 mg C/L
- Toxicity control: Test substance (12.7 mg/L) plus sodium benzoate (17.1 mg/L), equivalent to 20 mg C/L in total

Reference substance:
other: Sodium benzoate
Parameter:
% degradation (CO2 evolution)
Value:
ca. 10
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
ca. 36
Sampling time:
56 d
Results with reference substance:
The reference substance 90 and 93% degradation after 28 and 56 days, respectively.
The toxicity control showed 47 and 48% degradation after 28 and 56 days, respectively.

Day

% biodegradation

Test substance

Procedure control

Toxicity control

8

0

84

41

14

0

92

37

21

2

91

38

28

10

90

47

35

12

83

44

42

18

88

44

49

22

80

43

56

33

101

46

57*

36

93

48

* Day 57 values corrected to include any carry-over of CO2detected in Absorber 2

The concentration of the test substance did not show toxic effects to the seage micro-organisms used in the test. The toxicity control had 47 and 48% degradation after 28 and 56 days, respectively.

Validity criteria fulfilled:
yes
Conclusions:
Under the test conditions, the test substance is considered not to be readily biodegradable
Executive summary:

A study was performed to assess the ready biodgradability of the test substance in accordance with the OECD guideline 301B and EU method C.4 -C, in compliance with GLP.

The test substance in a mineral medium was inoculated with domestic sewage effluent and incubated for 56 days under aerobic conditions.

The test substance showed 10 and 36% degradation after 28 and 56 days, respectively. Therefore, the test substance is classified as not readily biodegradable under the conditions of the study.

The reference substance 90 and 93% degradation after 28 and 56 days, respectively, confirming the suitability of the inoculum and test conditions.

The toxicity control showed 47 and 48% degradation after 28 and 56 days, respectively, confirming the test substance did not have an inhibitory effect on the sewage treatment micro-organisms used in the study.

This study can be classified as an acceptable key study and satisfies the guideline requirement for a biodegradation in water screening test.

Description of key information

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information