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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
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Activated sludge from a municipal waste water treatment plant Mannheim, Germany
- The inoculum was collected from the aeration tank of the plant and aerated in the laboratory until use.
- A suitable aliquot of the activated sludge suspension was sieved by a finely woven mesh with a mesh size about 1 mm.
- To reduce the content of inorganic carbon in the blank controls the activated sludge was aerated with carbon dioxide free air for about 48 hours at 22 ± 2° C.
- At the day of exposure the suspension was washed one time with tap water. Therefore the aeration was stopped and the sludge was allowed to settle. After settling the supernatant was discarded and the remaining sludge suspension was filled up with tap water and the concentration of the sludge was adjusted to 6.0 g/L dry weight.
- Aliquots of 7.5 mL were added to the test vessels to obtain a activated sludge concentration of 30 mg/L dry weight.
Duration of test (contact time):
28 d
Initial conc.:
ca. 61 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
The following test assays were prepared:
- 2 blank control assays (BC)
- 2 test substance assays (TS)
- 1 inhibition control test assay (IH)
- 1 reference substance assay (RS)

- pH adjusted: yes, adjusted to 7.4 ± 0.2
- Test temperature: 22 ± 2° C
Reference substance:
Key result
% degradation (CO2 evolution)
< 10
Sampling time:
28 d
Details on results:
Kinetic of test substance (in %):
= 1 after 2 day(s)
= 2 after 7 day(s)
= 3 after 12 day(s)
= 3 after 23 day(s)
= 2 after 28 day(s)

Kinetic of reference substance (in %):
= 74 after 14 day(s)

Results with reference substance:
Degree of biodegradation of the reference substance after 14 days: 74 % CO2/ThCO2
Validity criteria fulfilled:
Interpretation of results:
under test conditions no biodegradation observed

Description of key information

Not readily biodegradable (according OECD criteria).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The biodegradability of 'zinc phthalocyanine sulfonate' was tested in a GLP guideline study conducted in compliance with OECD 301 B (Ready Biodgradability: CO2 Evolution Test). Based on the CO2 evolution < 10% biodegradation of the substance was observed after 28 days by domestic activated sludge from a municipal sewage treatment plant [BASF SE, 2012].