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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1999-09-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
1993
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Batch No.: Partie 1
Purity: not specified
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
- Handling of a poorly water-soluble test substance: the test substance was added in the required amount to the test vessel with about 180 mL deionized water. The mixture was stirred for 22 ± 2 hours to obtain an optimal solution. Then synthetic medium was added, the pH-value was adjusted to 7.5 ± 0.5, the inoculum was added and the test started.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Inoculum: Activated sludge from laboratory wastewater plants treating municipal sewage . Concentration of dry substance 1 g/L.
- Preparation of the inoculum: the inoculum was washed, brought to a concentration of 5 g/L dry substance and aerated for about 24 hours. 50 mL were added to a total volume of 250 mL to obtain a concentration of 1 g/L dry substance in the test.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
180 min
Test temperature:
20±2°C
pH:
7.5 ± 0.5
Dissolved oxygen:
>6.5 mg/L
Nominal and measured concentrations:
Nominal: 1000 mg/L
Details on test conditions:
- Test vessels: Erlenmeyer-vessel (nominal volume 250 ml)
- Test volume: 250 mL
- Synthetic medium: 8 mL/vessel 100-fold concentrated OECD medium
- Oxygen concentration during aeration: > 2.5 mg/L
- Oxygen concentration immediately before measurement: > 6.5 mg/L
- Duration of the measurement of oxygen consumption: 8-10 min
Reference substance (positive control):
yes
Key result
Duration:
180 min
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
- Remarks: The EC20 in the activated sludge respiration inhibition test is >100 mg/L. Disturbances in the biodegradation process of activated sludge are not to be expected if the test substance is correctly introduced into adapted wastewater treatment plants at low concentrations.
- Blank controls oxygen uptake rate: 26 mg O2/g*h
- Coefficient of variation of oxygen uptake rate in control replicates: <15%
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC50: ca. 5.8 mg/L
Validity criteria fulfilled:
yes
Conclusions:
The EC50 was determined to be >1000 mg/L (nominal).
Executive summary:

The Inhibition of Oxygen Consumption by Activated Sludge by test item in the Activated Sludge Respiration Inhibition Test was determined according to OECD Guideline 209.

The EC20, EC50 and EC80 after incubation for 180 min were both >1000 mg/L.

Description of key information

The Inhibition of Oxygen Consumption by Activated Sludge by test item in the Activated Sludge Respiration Inhibition Test was determined according to OECD Guideline 209.

The EC20, EC50 and EC80 after incubation for 180 mins were both >1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
1 000 mg/L

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