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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:
17 May - 14 Jun 2005
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)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge was collected on 13 May 2005 from the municipal waste water treatment plant Neustadt/Weinstrasse, Lachen-Speyerdorf
- Method of cultivation: The sludge was continuously aerated and washed with tap water and OECD medium
- Concentration of suspended solids: 12.78 g/L
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
other: TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium as recommended by the guideline
- Test temperature: 21 ± 1 °C
- Aeration of dilution water: All vessels were aerated overnight with CO2-free air prior to test start and during the test
- Suspended solids concentration: 25 mg/L

TEST SYSTEM
- Culturing apparatus: 2 L Glass bottles, 1500 mL fill volume
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: Aeration with CO2-free air
- Details of trap for CO2: Outgoing air from the test vessels passed two serial bottles containing 0.25 M NaOH solution
- Other:

SAMPLING
- Sampling frequency: Measurement of evolved CO2 on days 2, 4, 6, 8, 10, 14, 21, 28 and 29
- Sampling method: 0.5 mL aliquots of the NaOH solution was sampled at each time point and analysed using a TOC 5050A (Shimadzu)

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 vessels
- Abiotic sterile control: 1 vessel
- Toxicity control: 1 vessel
Reference substance:
aniline
Parameter:
% degradation (CO2 evolution)
Value:
85.2
Sampling time:
28 d
Details on results:
- The toxicity control attained 98.3% degradation.
- Abiotic degradation was 26.6%.
Results with reference substance:
The reference substance attained 79.9% degradation after 28 days.

Table 1: Percentage of Degradation

Day

% Degradation

Reference

Test Item (mean of duplicates)

Abiotic Control

Toxicity Control

2

2.6

1.7

3.4

3.2

4

26.5

24.1

3.1

53.5

6

56.1

47.5

11.3

68.7

8

66.5

57.4

16.0

75.8

10

71.1

61.3

8.6

79.7

14

76.2

72.9

17.6

86.7

21

85.0

88.3

22.9

97.5

28

77.6

83.0

28.0

99.6

29

79.9

85.2

26.6

98.3

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable

Description of key information

Readily biodegradable: 85.2% in 28 d (OECD 301 B)

Key value for chemical safety assessment

Additional information

There is one study available investigating the ready biodegradability of N-methyl-N-(C18-(unsaturated)alkanoyl)glycine (EC 701-177-3). This study was conducted according to the OECD guideline 301B using non-adapted activated sludge from a municipal waste water treatment plant. 20 mg/L test substance (based on TOC) was inoculated with 25 mg/L domestic, non-adapted activated sludge for 28 d under aeration with CO2-free air. Inoculum blanks, an abiotic sterile control and a toxicity control were run in parallel. CO2 was trapped in bottles containing 0.25 M NaOH solution and the evolution of CO2 concentration was followed by TOC analysis in regular intervals. After 28 d incubation, the test item was degraded by 85.2% in terms of CO2 evolution. Thus, it can be concluded that N-methyl-N-(C18-(unsaturated)alkanoyl)glycine (EC 701-177-3) is readily biodegradable according to the OECD guideline criteria.