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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Study initiation date - 18 February 1999; Experiment start date - 24 February 1999; Experiment completion date - 03 March 1999; Study completion date - 24 March 1999.
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
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Identity: FAT 40'574/B
Batch: WP 23/99
Purity: Approx. 75 %
Appearance: Solid, dark-red powder
Storage: At room temperature at about 20 °C
Expiration Date: 08 February 2006
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
1.0 g/500 ml of the test substance in deionized water. 500 mg/l of the reference substance in deionized water.
Test organisms (species):
activated sludge, industrial
Details on inoculum:
Test system: Activated sludge of a communal sewage treatment plant (ARA-Pro Rheno Basel) collected on February 23, 1999

Sludge pre-treatment: The inoculum was prepared 1 day prior to the experimental start. The freshly collected activated sludge was washed 3 times with tap water. Subsequently the sludge was aerated. A sample of the activated sludge was taken to determine the dry weight of the suspended solids. The final concentration of the inoculum was adjusted to about 5.0 g/l suspended solids. For the storage over night synthetic sewage feed was added depending on the sludge concentration.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21.0 - 21.2 °C
pH:
8.2 - 8.5
Dissolved oxygen:
7.4 - 10.0
Nominal and measured concentrations:
Nominal: 25.6, 64, 160, 400 and 1000 mg/l of the test substance.
3.2, 10 and 32 mg/l of the reference substance.
Details on test conditions:
Sludge dry weight: 1.56 g/l suspended solids
Test volume: 100 ml
Test duration: 3 h
Aeration: 0.1 - 0.2 l/min by Pasteur pipette
Estimation technique: O2 - consumption, measured with an oxygen sensitive electrode system: OXI DIGI 530 (SOP: 00 109)
Reference substance (positive control):
yes
Remarks:
3,5 - Dichlorophenol
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 1 000 mg/L
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Results with reference substance (positive control):
IC50 (3 h) of the reference substance 3,5-Dichlorophenol: 15 mg/l.
Validity criteria fulfilled:
yes
Conclusions:
An IC50 value for the test substance was found to be greater than 1000 mg/L.

Executive summary:

The objective of this study was the determination of the test substance concentration, which reduces the respiration activity of activated sludge by 50 % (IC50 value). This study was conducted according to OECD test guideline 209 in a GLP-certified laboratory. Activated sludge of a communal sewage treatment plant (ARA-Pro Rheno Basel) was inoculum used for this study. 3,5 -Dichlorphenol served as positive control. The test substance concentration was 25.6, 64, 160, 400 and 1000 mg/l. The respiration rate of an activated sludge fed with a standard amount of synthetic sewage feed was measured after a contact time of 3 hours. Based on the findings of this study, the IC50 value for the test substance was found to be greater than 1000 mg/L.

Description of key information

The IC50 value for the test substance was found to be greater than 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

Additional information

The objective of this study was the determination of the test substance concentration, which reduces the respiration activity of activated sludge by 50 % (IC50 value). This study was conducted according to OECD test guideline 209 in a GLP-certified laboratory. Activated sludge of a communal sewage treatment plant (ARA-Pro Rheno Basel) was inoculum used for this study. 3,5 -Dichlorphenol served as positive control. The test substance concentration was 25.6, 64, 160, 400 and 1000 mg/l. The respiration rate of an activated sludge fed with a standard amount of synthetic sewage feed was measured after a contact time of 3 hours. Based on the findings of this study, the IC50 value for the test substance was found to be greater than 1000 mg/L.