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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:
test procedure in accordance with national standard methods
Qualifier:
according to
Guideline:
ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source: Activated sludge from the municipal treatment plant of a community near the testing facility.

Duration of test (contact time):
29 d
Initial conc.:
26 mg/L
Based on:
test mat.
Initial conc.:
20 mg/L
Based on:
TOC
Details on study design:
TEST CONDITIONS
- Composition of test medium: A total volume of 1500 mL containing: 38.5 mg test substance, 7.5 mL inoculum, 19.5 mL inorganic medium and 1473 mL water.
- pH: 7.2 - 7.4 throughout the test
- Stock solution of reference substance: 473.5 mg/L (TOC = 370 mg/L)
- Sampling/analysis: CO2-production in the controls and each treatment group at daily intervals from day 0 to day 28.

TEST SYSTEM
- Number of culture flasks/concentration: 2

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Toxicity control: 1
- Inhibition control: 1
Reference substance:
aniline
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 90 - <= 100
Sampling time:
28 d
Details on results:
- Duration of the adaptation period of the test substance: 3 days
- Duration of the degradation period of the test substance: 12 days
- ca. 9% biodegradation was seen after 3 days
- ca. 60% biodegradation was seen after 12 days
- 100% biodegradation was seen after 28 days

The 10-day window criterion was met.
Results with reference substance:
80 - 90% biodegradation after 14 days

Description of key information

The substance is readily biodegradable as observed in a ready biodegradability test according to ISO DIN 9439.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation potential of the substance in water was determined in a screening study according to ISO DIN 9439 (CO2 -Evolution Test) (BASF, 1999). In this study 26 mg/L test substance (20 mg/L based on TOC) was inoculated with non-adapted activated sludge from predominantly domestic sewage for 28 days under aerobic conditions. During the incubation period degradation was followed by determining the CO2-production in the controls and each treatment group at daily intervals. After the 28 -day incubation period 100% of the test substance was biodegraded. Approximately 10% degradation was seen at day 3 and the pass level of 60% degradation was reached after about 12 days. Therefore, the 10 -window criterion was met. Based on these findings, the test substance is classified as readily biodegradable.

These findings are further supported by findings from a biodegradation screening study according to EC TM C4 -D. In this study, 100 mg/L test substance was inoculated with activated sludge for 28 days and the oxygen consumption compared to a blank control. After 28 -days exposure 88.3% degradation was determined as BOD/ThOD*100. The lag phase lasted 2 days, the beginning of the plateau phase was determined at day 10. Therefore, the 10 -d window criterion was met. These findings confirm the ready biodegradability of the substance.