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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:
2016-09-06 to 2016-11-09
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
May 2008
Deviations:
no
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: Sewage treatment plant Rossdorf, Germany
- Conditioning: coarse particles removed by settling for 15 minutes + decantation of upper layer.
- Preparation of inoculum for exposure: aerated for 2 days
- Concentration of sludge: 3.5 g dry material /L
Duration of test (contact time):
28 d
Initial conc.:
103.7 mg/L
Based on:
test mat.
Initial conc.:
253 mg/L
Based on:
ThOD
Remarks:
ThOD(NH4)
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: reconstitued test water, according to OECD guideline
- Test temperature:
- pH: 22°C +/- 1°C
- pH adjusted: no
- Suspended solids concentration: in test flasks, 28.7 mg sludge/L
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL.
- Number of culture flasks: 7, 2 replicates with test ietm, 2 inoculum control, 1 procedure control, 1 abiotic control and 1 toxicity control
- Measuring equipment: BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany
- Test performed in closed vessels
- Details of trap for CO2 and volatile organics if used: Potassium hydroxide solution (45%)

RECORDINGS
- Frequency: daily recordings


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 1 replicate
- Abiotic sterile control: yes, 1 replicate
- Toxicity control: yes, 1 replicate


Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
50
St. dev.:
1.41
Sampling time:
12 d
Remarks on result:
other: mean of 2 measurements at end of 10-day window (12d)
Details on results:
On day 2, the mean biodegradation of 10 % was reached. At the end of the 10-day window (day 12), the mean biodegradation was 50%. The biodegradation at test end (28d) was 53%. The degradation rate did not reach 60 % within the 10-day window or after 28 days. Therefore the test item is not readily biodegradable.

A summary of the biodegradation rates (%) are presented here:

Time (days) Test item   Procedure control Toxicity control
Rep 1 Rep 2
1 8 8 29 11
2 19 19 42 18
4 42 42 65 49
6 46 44 71 50
8 49 45 76 52
10 49 47 76 53
12 52 48 77 56
16 55 51 78 59
20 56 50 80 58
24 56 50 86 57
28 56 50 86

57

The reference item was sufficiently degraded (to 78% after 14 days), which confirms the suitability of the used aerobic actived sludge.

The toxicity control, showed 58 % biodegradation within 14 days and 57% after 28 days. The test item was hence found not to be inhibitory to the activated sludge.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item was found to be not readily biodegradable. Up to 50 % biodegradation was observed at the end of the 10-day window and 53 % at the end of the study, after 28 days.

Description of key information

Not readily biodegradable (53 % after 28 days, OECD 301 F).

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The ready biodegradability of the test item was assessed according to OECD 301 F, manometric respirometry. The test set up consisted of 2 replicate flasks for the test item (103.7 mg/L, 253 mg ThOD/L), 2 inoculum controls, 1 procedure control with reference substance sodium benzoate (103.3 mg/L, 172.1 mg ThOD/L), 1 abiotic control and 1 toxicity control.

The test item was found to have degraded 10 % on day 2 of the experiment. At the end of the 10 -day window (day 12), the average biodegradation was 50 %. Hence, the 10 -day window criteria was not fulfilled. At the end of the experiment (28 days), the biodegrdation rate observed was 53%. It is hence concluded that the substance is not readily biodegradable.

Results with the reference item showed that the aerobic activated sludge for the experiment was suitable as the biodegradation observed was 78 % after the 10 -day window.

The biodegradation in the toxicity control reached 58 % after 10 -day window and 57% at the end of the study. It was thus concluded that the test item is not inhibitory to the microorganisms in the activated sludge.