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Environmental fate & pathways

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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
Deviations:
not applicable
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Test organisms:
-Type : mixed population of aquatic microorganisms (activated sludge)
-Origin : discharge of a wastewater plant treating predominantly domestic sewage (Wupper area water authority)
-Date of collection : 1999-06-21
-no pretreatment

Inoculum:
-Origin : discharge of a wastewater plant treating predominantly domestic sewage (Wupper area water authority)
-pretreatment: separation of coarse particles by filtration. Aeration of filtrate.
-concentration in test solution: 0.5 mL/L
Duration of test (contact time):
28 d
Initial conc.:
19.2 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
Test conditions:
-Incubation time: 28 days
-Incubation temperature: 22 ± 2 °C
-Concentration of stock solution: 1.0 g/L
-Volume: 1000 mL medium + 0.5 mL inoculum
-pH value: 7.4 ± 0.2
Reference substance:
benzoic acid, sodium salt
Remarks:
-Purity: 99 %, -initial concentration: 19.8 mg/L DOC
Key result
Parameter:
% degradation (DOC removal)
Value:
44
Sampling time:
28 d
Parameter:
% degradation (DOC removal)
Value:
46
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
46
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
43
Sampling time:
21 d
Results with reference substance:
Degradation of reference compound:
- 96 % after 7 days
- 97 % after 14 days
- 98 % after 21 days
- 100 % after 28 days
Validity criteria fulfilled:
yes
Remarks:
(- In the toxicity control degradation rates < 35 % (based on total DOC) within 14 days. - Replicates difference < 20 %)
Interpretation of results:
not readily biodegradable
Conclusions:
Within 28 days a degradation of 44 % was determined according to EU method C.4-B (Modified OECD Screening Test). Therefore, the test item is not readily biodegradable.
Executive summary:

The study was performed according to EU method C.4-B (Modified OECD Screening Test), which is equivalent to

OECD Guideline for Testing of Chemicals No. 301 E (Ready biodegradability: Modified OECD). Acitivated sludge, (domestic, non-adapted, 0.5 mL/L) was exposed to the test item for 28 days to a nominal concentration of 19.2 mg/L based on DOC. The mixture was incubated at 22 ± 2 °C. The degree of biodegradation is calculated by expressing the concentration of DOC removed (corrected for that in the blank inoculum control) as a percentage of the concentration initially present. Toxicity control showed that the used concentration of the test item was not toxic to bacteria (toxicity control: 72 % degradation within 28 days, based on total DOC).

The 28-day degradation was 44 % for the test item and 100 % for the positive control (with reference substance benzoic acid, sodium salt).

In conclusion the test item is not readily biodegradable. The biodegradation study is classified as acceptable and can be used for assessment.

Description of key information

Within 28 days a degradation of 44 % was determined according to EU method C.4-B (Modified OECD Screening Test). Therefore, the test item is not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information