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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 September 2003 - 17 October 2003
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
certificate issued on 5 October 2001
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: from the Marl-Ost municipal sewage treatment plant; collected on September 17, 2003 (the day of test start)
- Storage conditions: not reported; assumed none
- Storage length: none (seemingly the inoculum was used on the day of collection)
- Preparation of inoculum for exposure: in accordance with specifications in the laboratory (not further specified)
- Concentration of sludge: dry matter: 3.5 g/L
Duration of test (contact time):
28 d
Initial conc.:
20.6 mg/L
Based on:
test mat.
Remarks:
replicate 1
Initial conc.:
55.1 mg/L
Based on:
ThCO2
Remarks:
replicate 1
Initial conc.:
20.7 mg/L
Based on:
test mat.
Remarks:
replicate 2
Initial conc.:
54.7 mg/L
Based on:
ThCO2
Remarks:
replicate 2
Initial conc.:
ca. 15 other: mg C/L
Based on:
test mat.
Remarks:
calculated from the molecular formula (C-content = 72.34%)
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to OECD 301 B
- Additional substrate: no
- Test temperature: 20.1 - 22.7°C
- pH: on day 28: 7.5 (in both inoculumn blanks), 7.6 (in both test substance replicates and the reference substance solution)
- pH adjusted: not reported
- Aeration of dilution water: yes, at least 24 hours prior to test start
- Suspended solids concentration: 23.3 mg/L
- Continuous darkness: not reported, but assumed 'yes'

TEST SYSTEM
- Culturing apparatus: not reported
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: aeration prior to test start
- Measuring equipment: degradation was follwoed via TIC analysis (Shimadzu carbon analyzer) of the bound CO2
- Details of trap for CO2 and volatile organics if used: CO2 was bound in the form of sodium carbonate in sodium hydroxide solution

SAMPLING
- Sampling frequency: at test start (t=0 days) and after 4, 8, 11, 14, 18, 22, 28 and 29 days
- Sampling method: from the NaOH bottles duplicate samples were analysed, if necessary samples were diluted (no further specifications)
- Sample storage before analysis: not reported, assumed none

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Abiotic sterile control: no
- Toxicity control: no
- Other: 1 procedure control (with reference substance)
Reference substance:
benzoic acid, sodium salt
Remarks:
25.0 mg/L based on test. mat. / 55.1 mg/L based on ThCO2 / 14.6 mg C/L
Key result
Parameter:
% degradation (CO2 evolution)
Value:
-8
Sampling time:
28 d
Details on results:
The negative value of % degradation is due to mathematical calculation.
Results with reference substance:
87% degradation after 14 days (98% after 28 days)

Table: mg TIC/L 0.05 N NaOH

Test duration

Blank

1

Blank

2

Blank mean

Test item 1

Test item 2

Reference control

0

1.345

1.641

1.49

1.199

1.262

1.299

4

5.786

5.487

5.64

4.592

3.934

28.02

8

7.644

9.098

8.37

6.423

5.611

40.05

11

8.508

10.97

9.74

7.013

6.397

44.38

14

9.165

11.51

10.34

7.687

7.113

48.37

18

9.866

12.18

11.02

8.248

7.685

48.22

22

10.39

13.01

11.70

8.509

8.234

51.03

28

11.18

13.91

12.55

9.141

8.981

56.41

29

11.50

14.20

12.85

9.352

9.250

55.90

 

Table: Percentages degradation in the reference control and in the test vessels

Test duration

Reference control

Test item 1

Test item 2

Test item mean

0 *

0

-1

-1

-1

4

51

-2

-4

-3

8

72

-4

-6

-5

11

79

-6

-7

-7

14

87

-6

-7

-7

18

85

-6

-7

-7

22

90

-7

-8

-8

28

100

-8

-8

-8

29 **

98

-8

-8

-8

* Day 0 corresponds to the value after 30 minutes

** After acidification

Validity criteria fulfilled:
not specified
Interpretation of results:
not readily biodegradable
Conclusions:
The test item is not readily biodegradable.
Executive summary:

The biodegradability of the test item was examined in a study according to OECD TG 301B, and in compliance with GLP criteria. The test substance, at a concentration of ca. 20.6 mg/L, was inoculated with non-adapted activated sludge from a municipal sewage treatment plant for 28 days under aerobic conditions. Evolution of CO2 was monitored in duplicate by means of TIC analysis at days 0, 4, 8, 11, 14, 18, 22 and 28 (and in addition at day 29 after acidification). Percentages biodegradation were calculated from TIC and ThCO2. In a reference control with sodium benzoate, 87% biodegradation was observed after 14 days showing the inoculum to have sufficient biological activity.

Under conditions of the test, the substance biodegraded -8% (negative value due to mathematical calculation). The substance is concluded to be not readily biodegradable.

Description of key information

The biodegradability of the substance is examined based on read-across from data available for a close structural analogue.

The biodegradability of the structural analogue was examined in a study according to OECD TG 301B, and in compliance with GLP criteria. The test substance, at a concentration of ca. 20.6 mg/L, was inoculated with non-adapted activated sludge from a municipal sewage treatment plant for 28 days under aerobic conditions. Evolution of CO2 was monitored in duplicate by means of TIC analysis at days 0, 4, 8, 11, 14, 18, 22 and 28 (and in addition at day 29 after acidification). Percentages biodegradation were calculated from TIC and ThCO2. In a reference control with sodium benzoate, 87% biodegradation was observed after 14 days showing the inoculum to have sufficient biological activity.

Under conditions of the test, the substance biodegraded -8% (negative value due to mathematical calculation). The substance is concluded to be not readily biodegradable.

Key value for chemical safety assessment

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

Additional information