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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:
Feb 2019 - Aug 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: municipal wastewater treatment plant Markkleeberg
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Remarks:
direct weight; ThOD 1.71 mg O2/mg
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 21.6 - 22.5 ° C
- pH: 7.6 - 9.5
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 ml test flasks, made of brown glass, filled with 250 ml test solution
- Number of culture flasks/concentration: 2

SAMPLING
- Sampling frequency: 1 hour

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks
- Abiotic sterile control: considered not necessary
- Toxicity control: 2 flasks
- Reference: 2 flasks
Reference substance:
acetic acid, sodium salt
Remarks:
Purity: 99.7%, 100 mg/L
Key result
Parameter:
% degradation (O2 consumption)
Value:
60
Sampling time:
28 d

Overview of the percentage removal 

Test variant

Percentage removal [%]

After 10-d window

After
14 d

At beginning of plateau

= at 90 % of max. removal

At end of test

Maximum

Test item

54

54

54

60

60

Reference item

87

90

84

93

93

Toxicity control

46

48

50

56

56

  

The difference of extremes of replicate values of the removal of the test chemicals at the plateau, at the end of the test or at the end of the 10-d window, was less than 5 %.

 The pass level for ready biodegradability of 60 % of ThOD was not reached by the test item. At the end of the 10-d window a maximum degradation of 54 % was found, therefore the test item is considered as not readily biodegradable. The removal of the test item was 60 % after 28 days.

The percentage degradation of the reference item has reached the pass level within 14 days. During a time period of 14 days a percentage removal of 90 % was obtained. The maximum removal of the reference item was 93 %.

The test item can’t be assumed to be inhibitory, because the toxicity control, containing both the test item and a reference item, shows with 56 % more than 25 % degradation within 14 days.

 

The oxygen uptake of the inoculum blank was 5.2 mg/L in 28 days.

 

The test criteria were met and the test is considered valid.

 

No observations were made which might cause doubts concerning the validity of the study outcome.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
The pass level for ready biodegradability of 60 % of ThOD was not reached by the test item. At the end of the 10-d window a maximum degradation of 54 % was found, therefore the test item is considered as not readily biodegradable within the 10-days-window. The removal of the test item was 60 % after 28 days.
Executive summary:

The study was performed to determine the ready biodegradability of the test item Ethylphthalyl ethyl glycolate according to OECD guideline 301 F Manometric Respirometry Test.

In the study a test item concentration of 100 mg/L Ethylphthalyl ethyl glycolate, a reference batch with 100 mg/L sodium acetate, a toxicity control with both test item and reference item with the same concentration and an inoculum blank were tested, each in duplicate. The used inoculum was a sewage effluent.

 The pass level for ready biodegradability of 60 % of COD was not reached by the test item. At the end of the 10-d window a maximum degradation of 54 % was found, therefore the test item is considered as not readily biodegradable. The removal of the test item within 28 days was 60 %.

The percentage degradation of the reference item has reached the pass level within 14 days. During a time period of 14 days a percentage removal of 90 % was obtained. The maximum removal of the reference item was 93 % within 28 days.

The test item can’t be assumed to be inhibitory, because the toxicity control, containing both the test item and a reference item, shows with 56 % more than 25 % degradation within 14 days.

 

 The validity criteria were met. The test results can be considered valid.

 

Description of key information

Ready biodegradability was investigated in a Manometric Respirometry Test according to OECD Guideline 301 F resp. EU Method C.4-D.

The pass level for ready biodegradability of 60 % of ThOD was not reached by the test item. At the end of the 10-d window a maximum degradation of 54 % was found, therefore the test item is considered as not readily biodegradable within the 10-days-window. The removal of the test item was 60 % after 28 days.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window
Type of water:
freshwater

Additional information