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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:
2020-02-25 to 2020-04-14
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)
Version / remarks:
July 17, 1992
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
May 2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, industrial (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Domestic wastewater plant of Rossdorf, Germany.
- Preparation of inoculum for exposure: The aerobic activated sludge used for this study was deposited for 15 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.
- Concentration of sludge: 3.5 g dry material per litre were mixed with test water (see 6.5) and aerated until test start at the same day. This suspension was used for the experiment.
Duration of test (contact time):
>= 28 d
Initial conc.:
>= 103 mg/L
Based on:
test mat.
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 ultrapure 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 7.4.
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 ultrapure water.
The pH was adjusted to pH 7.5 with 1m HCl solution.

- Test temperature: 22°C
- pH: 7.5-7.6
- pH adjusted: no
- Suspended solids concentration: 3.5 g dry weight/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks of approx. 500 ml volume
- Number of culture flasks/concentration: 2
- Measuring equipment: BSB/BOD Sensor System
- Details of trap for CO2 and volatile organics if used: Potassium hydroxide solution (45%)

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

Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 0
Sampling time:
28 d
Key result
Parameter:
ThOD
Value:
ca. 0 other: mg O2/L
Results with reference substance:
71% degradation after 14 days and 77% degradation after 28 days.

Biodegradation of test item

(R)-3-Amino-2-(2,4-difluorophenyl)-1,1-difluoro-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol L-tartrate never reached 10 % degradation during the incubation period of 28 days. The mean biodegradation at test end after 28 days was 0% (ThODNH4, ThODNO3).

Controls

Toxicity Control: In the toxicity control containing both, the test item and the reference item sodium benzoate, 40% (ThODNH4) biodegradation was noted within 14 days and 45% (ThODNH4) biodegradation after 28 days of incubation (38% and 42% based on ThODNO3).

Abiotic control: The oxygen demand in the abiotic control was 0 mg/L during the test duration.

Inoculum Control: The oxygen demand of the inoculum control (medium and inoculum) was 20 mg O2/L and thus not greater than 60 mg O2/L within 28 days as required by the test guideline.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The degradation rate of (R)-3-Amino-2-(2,4-difluorophenyl)-1,1-difluoro-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol L-tartrate never reached 60% within the incubation period of 28 days.
Therefore, (R)-3-Amino-2-(2,4-difluorophenyl)-1,1-difluoro-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol L-tartrate is considered to be not readily biodegradable.
Executive summary:

The biodegradation of (R)-3-Amino-2-(2,4-difluorophenyl)-1,1-difluoro-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol L-tartrate was studied in aerobic activated sludge from a domestic wastewater plant according to OECD guideline 301F and EEC method 440/2008/EC C.4 -D in a manometric respirometry test. The test item was exposed to aerobic 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. The test included an abiotic control, a toxicity control and an inoculum blank control. All controls were valid.

(R)-3-Amino-2-(2,4-difluorophenyl)-1,1-difluoro-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol L-tartrate never reached 10 % degradation during the incubation period of 28 days. The mean biodegradation at test end after 28 days was 0% (ThODNH4, ThODNO3).

Description of key information

(R)-3-Amino-2-(2,4-difluorophenyl)-1,1-difluoro-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol L-tartrate never reached 10 % degradation during the incubation period of 28 days. The mean biodegradation at test end after 28 days was 0% (ThODNH4, ThODNO3).

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable
Type of water:
freshwater

Additional information