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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:
25 October 2016 to 02 December 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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)
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
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: from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Storage conditions: washed sample is maintained in mineral medium (acc yo OECD 310) on continuous aeration at approximately 21 ºC
- Storage length:< 1 day
- Preparation of inoculum for exposure: in oculum at concentration of 30 mg SS/L
Duration of test (contact time):
29 d
Initial conc.:
10 other: mgC/L
Based on:
act. ingr.
Initial conc.:
22.9 mg/L
Based on:
act. ingr.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to OECD301
- Test temperature: 22-24 °C,
- pH: pre-treatment 7.7; after adjustment 7.5-7.6; on day 28 7.5-7.7
- Aeration of dilution water: CO2-free air
- Suspended solids concentration: 30 mgSS/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 liter vessels
- Number of culture flasks/concentration: 2 vessels for controls, reference and test item, toxicity controls 1 velssel
- Method used to create aerobic conditions: bubbling of vessels with CO2-free air
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used: NaOH in Dreschel bottle (2 traps)

SAMPLING
- Sampling frequency: first absorber on day 0, 2, 6, 8, 10, 14, 21, 28 and 29; second absorber on day 0 and 29
- Sample storage before analysis: either analysed directly or stored frozen

CONTROL AND BLANK SYSTEM
- Inoculum blank: in duplicate
- Abiotic sterile control: NA
- Toxicity control: single veseel
Reference substance:
benzoic acid, sodium salt
Preliminary study:
No indication of adsorption (filtered solutions 84-93% of nominal C-content)
Test performance:
positive control and toxicity control showed sufficient degradation to pass the validity criteria
Key result
Parameter:
% degradation (CO2 evolution)
Value:
0
Sampling time:
21 d
Remarks on result:
other:
Key result
Parameter:
% degradation (CO2 evolution)
Value:
1
Sampling time:
28 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
9
Sampling time:
29 d
Remarks on result:
other: after acidification with HCl
Results with reference substance:
the reference study attained 78% degradation over 14 days and 77% degradation at the end of the study

Day

% Biodegradation

 

 

Procedure Control

Test Item

Toxicity Control

0

0

0

0

2

57

0

31

6

59

0

38

8

71

0

35

10

71

0

34

14

78

0

37

21

79

0

35

28

83

1

37

29

77

9

53

 

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The substance is not readily biodegradable
Executive summary:

In a CO2 evolution test the substance sludge was exposed to the substance over a 29 day period. No CO2 evolution was reported. Therefore the substance is considered not readily biodegradable.

Description of key information

In a CO2 evolution test sludge was exposed to the substance over a 29 day period. No CO2 evolution was reported. Maximum degradation 9%. Therefore the substance is considered not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information