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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:
2018-11-13 - 2018-12-11 (experimental phase)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
GLP
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
Commission Regulation 440/2008/EC, Method C.4-D of May 30, 2008: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008)
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", adopted July 17, 1992
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Hess. Ministerium für Umwelt, Klimaschutz, Landwirtschaft und Verbraucherschutz, Mainzer Straße 80, 55189 Wiesbaden, Germany
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At 20°C ± 5°C, in the desiccator in the dark
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany
- Preparation of inoculum for exposure:
Conditioning: The aerobic activated sludge used for this study was deposited for 60 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. 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 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.
- Concentration of sludge: 3.5 g dry material per litre
Duration of test (contact time):
28 d
Initial conc.:
>= 24.8 - <= 25.1 mg/L
Based on:
test mat.
Remarks:
ThOD NH4: 2.150 mg oxygen per mg test item
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium:
Reconstituted Test Water: Analytical grade salts were added to pure water to prepare the following stock solutions:
a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4 x 2 H2O, 0.5 g NH4Cl filled up with pure water to 1000 mL volume; The pH-value was 7.3.
b) 11.25 g MgSO4 x 7 H2O filled up with pure water to 500 mL volume
c) 18.2 g CaCl2 x 2 H2O filled up with pure water to 500 mL volume
d) 0.125 g FeCl3 x 6 H2O filled up with pure water to 500 mL volume
In order to avoid precipitation of iron hydroxide in the stock solution d), one drop of concentrated HCl per litre was added before storage.
50 mL of stock solution a) and 5 mL of the stock solutions b) to d) were combined and filled up to a final volume of 5000 mL with pure water.
The pH was adjusted to pH 7.2 with NaOH solution.
- Additional substrate: none
- Test temperature: 22°C ± 1°C
- pH: 7.3 (measured at the start of the test) / 7.1 to 7.2 (measured at the end of the test)
- pH adjusted: no
- Aeration of dilution water: aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight
- Suspended solids concentration: sludge suspension: 3.5 g dry material per litre
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL. Closed test flasks were incubated in a climatised chamber, BSB/BOD-Sensor-System
- Number of culture flasks/concentration: duplicates
- Measuring equipment: The closed test flasks were incubated in a climatised chamber under continuous stirring. The consumption of oxygen was determined by measuring the change of pressure in the flasks. Evolved carbon dioxide was absorbed in an aqueous solution (45%) of potassium hydroxide.
Measurement of Oxygen: The change of pressure in the test flasks was measured by means of a manometric method (BSB/BOD-Sensor-System®) each day.
Temperature: The temperature was recorded by means of the automated software AMR Wincontrol©.
pH-Value: pH-values were measured in procedure control, a separately prepared test flask with test item (to prevent loss of test item in the test flasks) and a separately prepared test flask without test item (control) at test start and in all flasks at the end of the test, except in the abiotic and toxicity control, using a pH-electrode WTW pH 340i.
- Test performed in closed vessels due to significant volatility of test substance: substance is not volatile
- Test performed in open system: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes, poisoned with CuSO4 (stock solution of 1 g/L)
- Toxicity control: yes
For details, see table in free-text field
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation.
The test item 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached a degradation of 10%. The mean biodegradation at test end after 28 days was 0% (ThODNH4).
The degradation rate of 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached 60% within the 10-day window or after 28 days.
Therefore, 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one is considered to be not readily biodegradable.
Results with reference substance:
The reference item sodium benzoate was sufficiently degraded to 82% after 14 days and to 88% after 28 days of incubation. The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The study was performed according to OECD TG 301F and EU Method C.4-D (GLP) with no deviation and is therefore considered to be of the highest quality (reliability Klimisch 1). The validity criteria of the test system are fulfilled, controls gave appropriate results. The test item 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached a degradation of 10%. The mean biodegradation at test end after 28 days was 0% (ThODNH4). Therefore, 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one is considered to be not readily biodegradable.
Executive summary:

The Ready Biodegradability of 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one was determined in a Manometric Respirometry Test under GLP. This study was designed to comply with the following methods:

Commission Regulation 440/2008/EC, Method C.4-D of: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008)

OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", adopted July 17, 1992

 

Material and Methods:

Test Species: Aerobic activated sludge (microorganisms from a domestic waste­water treatment plant) was supplied by the sewage treatment plant of Rossdorf,.

Test Design: The test item 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one was investigated for its ready biodegradability in a manometric respirometry test over a period of 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.

Endpoints: Degradation rate of test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

Test Item Loading Rate (initial concentration in medium C0): 102.2 mg/L corresponding to an oxygen demand of about 219.8 mg/L (ThODNH4)

Reference Item: Sodium Benzoate

Reference Item Loading Rate: 102.7 mg/L corresponding to an oxygen demand of about 171.2 mg/L (ThODNH4)

Test Conditions: 22°C ± 1°C, darkness

 

Results:

Biodegradation of 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one: The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation.

The test item 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached a degradation of 10%. The mean biodegradation at test end after 28 days was 0% (ThODNH4).

Therefore, 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one is considered to be not readily biodegradable based on ThODNH4.

Biodegradation of Sodium Benzoate: The reference item sodium benzoate was sufficiently degraded to 82% after 14 days and to 88% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

Biodegradation of the Toxicity Control: In the toxicity control containing both, the test item and the reference item sodium benzoate, 35% (ThODNH4) biodegradation was noted within 14 days and 36% (ThODNH4) biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

Description of key information

0 % biodegradation after 28 days [using the Manometric Respirometry Test of OECD 301F (EU Method C.4-C); GLP]

Key value for chemical safety assessment

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

Additional information

A reliability score of 1 was assigned for the test, in accordance with the criteria for assigning data quality in line with the principles described by Klimisch (1997).