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Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 09 Mar to 28 May 2021
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Batch/Lot number: 465884
Description: White to off-white to slightly yellow solid
Purity: 100%
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Treatment: The freshly obtained sludge was kept under continuous aeration until further treatment. Before use, the sludge was coarsely sieved (1 mm) and homogenized using a blender on medium speed for approximately 1 minute. After treatment, the concentration of suspended solids (SS) was
determined to be 3.9 g/L in the concentrated sludge as used for the test. The sludge was used as inoculum at a concentration of 7.7 mL per liter of mineral medium, leading to a final concentration SS of 30.0 mg/L.
Duration of test (contact time):
28 d
Initial conc.:
15 mg/L
Based on:
test mat.
Initial conc.:
25 mg/L
Based on:
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
- Composition of medium:
Stock solutions of mineral components:
A) 8.50 g KH2PO4
21.75 g K2HPO4
67.20 g Na2HPO4.12H2O
0.50 g NH4Cl
dissolved in Milli-RO water and made up to 1 L
B) 22.50 g MgSO4.7H2O dissolved in Milli-RO water and made up to 1 L.
C) 36.40 g CaCl2.2H2O dissolved in Milli-RO water and made up to 1 L.
D) 0.25 g FeCl3.6H2O dissolved in Milli-RO water and made up to 1 L.
- Additional substrate:
Mineral medium: 1 L mineral medium contains: 10 mL of solution (A),
1 mL of solutions (B) through (D) and Milli-RO water.
- Solubilising agent (type and concentration if used):
- Test temperature: 21 - 23 °C
- pH: 7.4 ± 0.2
- pH adjusted: no

- Culturing apparatus: 500 mL amber glass vessels. The end volume of medium was 244 mL, in order to obtain the required headspace-tovolume ratio.
- Number of culture flasks/concentration:
Test suspension: containing test item, silicon dioxide and inoculum (2 vessels).
Inoculum blank: containing inoculum and silicon dioxide (2 vessels)
Procedural control: containing procedural control item, inoculum and silicon dioxide (1 vessel).
Toxicity control: containing inoculum, silicon dioxide, test item and procedural control item (1 vessel).
Reference substance:
acetic acid, sodium salt
Preliminary study:
The first experiment performed on test item at a concentration of 48 mg/L.The results indicate that there is a potentially inhibitory effect, since <25 % biodegradation is observed in the toxicity control.
Key result
% degradation (CO2 evolution)
Sampling time:
28 d
Details on results:
The relative biodegradation values calculated from the measurements performed during the
test period revealed no biologically relevant biodegradation of test item, based on ThOD
(0 % and 4 % for vessel A and B, respectively).
In the toxicity control of the second experiment, more than 25 % biodegradation occurred
within 14 days (56 %, based on ThOD). Therefore, the test item was considered not to inhibit
microbial activity at the decreased concentration (15 mg/L) used in the second experiment.

The first experiment showed a potentially inhibitory effect of test item at a concentration of 48 mg/L. This effect was not observed in the second experiment, which was performed at a decreased concentration of 15 mg/L. Therefore, the lack of biodegradation in the second experiment cannot be caused by inhibitory effects. In conclusion, test item was not readily biodegradable under the conditions of the Manometric Respirometry Test.

Validity criteria fulfilled:
Interpretation of results:
not readily biodegradable
The substance is not readily biodegradable in the OECD 301F study.

Description of key information

The substance is not readily biodegradable in the OECD 301F study.

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable
Type of water:

Additional information