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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:
from 2011-07-12 to 2011-09-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
Dated May 30, 2008
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
adopted July 17, 1992
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Version / remarks:
January 1998
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: sewage plant for domestic sewage in Balatonfüred, Hungary
- Preparation of inoculum for exposure: The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in isotonic saline solution and again centrifuged. This procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 5 g dry material per litre was mixed with reconstituted water and then aerated until use (in this study 100 mL inoculum was prepared). Before use the sludge was filtered through cotton wool.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Initial conc.:
6.32 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: in accordance to the guideline
- Test temperature: 22 ± 2 °C
- pH: 7.42
- pH adjusted: no

TEST SYSTEM
- Culturing apparatus: Winkler bottles (300 mL, coded) with special neck and glass stoppers.
- Number of culture flasks/concentration:
16 (+2 reserve) bottles containing the test item and inoculum
16 (+2 reserve) bottles containing the reference item and inoculum (procedure control)
16 (+2 reserve) bottles containing only inoculum (inoculum control)
16 (+2 reserve) bottles containing the test item, reference item and inoculum (toxicity control)
Reference substance:
benzoic acid, sodium salt
Test performance:
The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item and functioned as a procedure control.
Key result
Parameter:
% degradation (O2 consumption)
Value:
0.2
Sampling time:
28 d
Details on results:
Correction for oxygen uptake for interference with nitrification:
The test item does not contain nitrogen. For this reason, total oxidised nitrogen (N) concentrations (nitrate and nitrite) were not measured after each oxygen measurement.
Errors due to not considering nitrification in the assessment by oxygen uptake of the biodegradability of test substances not containing nitrogen are marginal (not greater than 5 %), even if oxidation of the ammonium N in the medium occurs erratically as between test and blank vessels.
Key result
Parameter:
BOD5
Value:
0 other: mg O2/mg test item
Results with reference substance:
The reference item sodium benzoate was sufficiently degraded to a mean of 77.8 % after 14 days, and to a mean of 86.9 % after 28 days of incubation, based on ThODNH4. The percentage biodegradation of the reference item confirms the suitability of the used activated sludge inoculum.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test item can be considered to not be ready biodegradable. According to the test guidelines the pass level for ready biodegradability is removal of 60 % ThODNH4.
Executive summary:

The purpose of this study was to determine the ready biodegradability of 1,1'-(1,1,2,2-tetramethylethylene)dibenzene. The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days in accordance to OECD TG 301D, Regulation (EC) No 440/2008 Method C.4-E and EPA OPPTS 835.3110. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Under the test conditions the percentage biodegradation of the test item reached a mean of 0.2 % after 28 days based on ThODNH4. Therefore, the test item is considered to not be ready biodegradable. The reference item sodium benzoate was sufficiently degraded to a mean of 77.8 % after 14 days, and to a mean of 86.9 % after 28 days of incubation, based on ThODNH4, thus, confirming the suitability of the used activated sludge inoculum. In the toxicity control containing both, the test item and the reference item, a mean of 27.0 % biodegradation was noted within 14 days and 33.3 % biodegradation after 28 days of incubation. Thus, the test item can be assumed to not inhibit the activated sludge microorganisms.

Description of key information

Under the test conditions the percentage biodegradation of the material reached a mean of 0.2 % based on ThODNH4. Thus, the test item has to be considered as not ready biodegradable.

Key value for chemical safety assessment

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

Additional information

The purpose of this study was to determine the ready biodegradability of 1,1'-(1,1,2,2-tetramethylethylene)dibenzene. The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days in accordance to OECD TG 301D, Regulation (EC) No 440/2008 Method C.4-E and EPA OPPTS 835.3110. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Under the test conditions the percentage biodegradation of the test item reached a mean of 0.2 % after 28 days based on ThODNH4. Therefore, the test item is considered to not be ready biodegradable. The reference item sodium benzoate was sufficiently degraded to a mean of 77.8 % after 14 days, and to a mean of 86.9 % after 28 days of incubation, based on ThODNH4, thus, confirming the suitability of the used activated sludge inoculum. In the toxicity control containing both, the test item and the reference item, a mean of 27.0 % biodegradation was noted within 14 days and 33.3 % biodegradation after 28 days of incubation. Thus, the test item can be assumed to not inhibit the activated sludge microorganisms.