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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:
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)
Qualifier:
according to
Guideline:
ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Laboratory wastewater plants treating municipal and synthetic sewage
- Preparation of inoculum for exposure: At the day of exposure the suspension was washed one time with drinking water. Subsequently the aeration was stopped and the sludge was allowed to settle. After settling the supernatant was discarded and the remaining sludge suspension was filled up
with drinking water and the concentration oft the sludge was adjusted to 6.0 g/L dry weight.
- Initial cell/biomass concentration: 30 mg/L dry substance
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Test temperature: 22 ± 2 °C

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: pre-aeration 24 hours before test start
- Measuring equipment: carbon dioxide trap
- Test performed in open system: no

SAMPLING
- Sampling frequency: every other day

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Other: Inhibition control
Reference substance:
aniline
Parameter:
% degradation (CO2 evolution)
Value:
ca. 50 - ca. 60
Sampling time:
28 d
Results with reference substance:
Degree of biodegradation of the reference substance after 14 days: 76 % CO2/ThCO2

Degree of biodegradation (%CO2/ThCO2)

TEST DURATION (days)

 RS

 IH

 TS1

 TS2

 TS mv

 0

 0

 0

 0

 0

 0

 2

 2

 1

 4

 3

 5

 5

 40

 23

 8

 8

 8

 7

 52

 30

 12

 12

 12

 9

 57

 37

 15

 15

 15

 12

 69

 43

 18

 20

 19

 14

 76

 47

 21

 23

 22

 16

 81

 49

 24

 26

 25

 19

 85

 52

 29

 32

 31

 22

 88

 54

 33

 39

 36

 28

 92

 57

 46

 62

 54

RS: reference substance

IH: Inhibition control

TS1: Test substance assay 1

TS2: Test substance assay 2

TS mv: Test substance mean value

 

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Executive summary:

The conclusion that trimethyl benzene-1,2,4 -tricarboxylate was not readily biodegradable in this carbon dioxide evolution test based on the quantitative determination of the formed carbon dioxide in the test substance assays by comparison with the calculated maximal theoretical carbon dioxide production. The required pass level for ready biodegradability within a ten days window was not reached. The degree of biodegradation after an exposure period of 28 days was 50-60 % CO2/ThCO2 in this test.

The degree of biodegradation was calculated as mean of the values from two test assays at the end of exposure. Based on the rate of biodegradation of 50-60 % CO2/ThCO2 at the end of exposure the test substance can be evaluated as partly or moderately biodegradable in this test. The results in this study are consistent with all validity criteria and the test is valid according to the test guideline of this study. No deviations from the test guidelines or other incidents occurred during the course of the reported test, which may have influenced the results.

Description of key information

Biodegradation: not readily biodegradable.

Key value for chemical safety assessment

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

Additional information

The experimental data show that, although significant biodegradation occurred, trimethyl benzene-1,2,4 -tricarboxylate was not readily biodegradable in water, despite the opposite results coming from (Q)SAR estimations.