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Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 16 April 2021 to 14 May 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Version / remarks:

July 17, 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch/Lot number: 381890
Purity: 99.8%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Secondary effluent, microorganisms from a domestic wastewater treatment plant. The secondary effluent was supplied from one of the sewage plant for domestic sewage in Veszprém county, Hungary.
- Preparation of inoculum for exposure: After collection of a fresh sample of secondary effluent could settle for approximately one hour, then the decanted effluent or filtrate was aerated until use.

Duration of test (contact time):

28 h

Initial conc.:

4.4 mg/L

Based on:

test mat.

Details on study design:

TEST CONDITIONS
- Composition of medium:
a) Solution: KH2PO4 2.125 g
K2HPO4 5.4375 g
Na2HPO4 x 12H2O 16.795 g
NH4Cl 0.125 g
Deionised water ad 250 mL
b) Solution: MgSO4 x 7 H2O 5.625 g
Deionised water ad 250 mL
c) Solution: CaCl2 x 2 H2O 9.10 g
Deionised water ad 250 mL
d) Solution: FeCl3 x 6 H2O 0.25 g
Deionised water ad 1000 mL
- Test temperature: 22 oC
- pH: 7.46
- Aeration of dilution water: yes

TEST SYSTEM
- Culturing apparatus: BOD bottles (300 mL) with special neck and glass stoppers.
- Number of culture flasks/concentration: at least 10 bottles
- Measuring equipment: The COD (chemical oxygen demand) of the test item was determined in the analytical department of the test facility using Lovibond® COD Measuring System. The oxygen concentrations were measured with an oxygen meter with a stirring O2 electrode.
- Test performed in closed vessels: yes

SAMPLING
- Sampling frequency: Oxygen measurements were performed in duplicate on days 0, 7, 14, 21 and 28.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Only filtered inoculum was added to 3.38 litres of aqueous test medium.
- Toxicity control: The Test Item (340.0 mL) and the reference item stock solutions (34.0 mL) were mixed into 3.40 litres of aqueous test medium corresponding to 4.4 mg/L test item (ThOD of 5.940 mg O2/L) and 3.6 mg/L reference item (ThOD of 6.012 mg O2/L).

Reference substance:

benzoic acid, sodium salt

Preliminary study:

A 14-day preliminary test was conducted to determine the approximate biodegradation of the test item. It showed 6.7% biodegradation after 14 days of exposure.

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

Under the test conditions the percentage biodegradation of Test Item reached a mean of 0.0 % after 28 days based on the COD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % COD/ThOD. Therefore, the test item is considered not readily biodegradable.

Key result

Parameter:

COD

Value:

0 mg O2/g test mat.

Results with reference substance:

The reference item Sodium benzoate was sufficiently degraded to a mean of 75.8 % after 14 days,
and to a mean of 91.7 % after 28 days of incubation, based on ThOD, thus confirming the suitability
of the used inoculum.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the test conditions the percentage biodegradation of Test Item reached a mean of 0.0 % after 28 days based on the COD of the test item. The test item is considered not readily biodegradable.

Executive summary:

The test item was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days, according to OECD Guideline 301 D under GLP.
Under the test conditions the percentage biodegradation of Test Item reached a mean of 0.0 % after 28 days based on the COD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % COD/ThOD. Therefore, the test item is considered not readily biodegradable.

Description of key information

Under the test conditions the percentage biodegradation of Test Item reached a mean of 0.0 % after 28 days based on the COD of the test item. The test item is considered not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater