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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Principles of method if other than guideline:
This test method is equal to OECD Guideline 209 (1984).
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
TEST ORGANISM:
- mixed population of aquatic microorganisms, origin of an aeration tank of a domestic sewage treatment plant (Municipal STP Cologne-Stammheim, Germany)
- pretreatment: aeration at 20 °C +/- 2 °C, daily feed with synthetic medium
- pH of the suspension before application: 7.6
- pH of the synthetic sewage feed : 7.5 ± 0.5
- test concentration of the activated sludge: 800 mg/l suspended solids
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
No data
Test temperature:
19.1 °C (concerning the highest concentration of 1000 mg/l)

pH:
pH: 7.7 (concerning the highest concentration of 1000 mg/l)

Dissolved oxygen:
oxygen (mg/l): O2-start 6.3; O2-end 3.9 (concerning the highest concentration of 1000 mg/l)

Salinity:
No data
Details on test conditions:
TEST CONDITIONS:
- type of application: direct weighing
- temperature: 20 +/- 2 °C
- stirring period before start of incubation time: 16 h
- test concentration: 3 (10, 100, 1000 mg/l)
- test parameter: respiration rate
- aeration: permanent
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol, concentration (5, 10, 20 mg/l), purity 97 %
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: probit analysis
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: probit analysis
Details on results:
Test concentrations are given as nominal concentrations and were not confirmed by analytical methods. The physico-chemical oxygen consumption has been determined at 1000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations.
Results with reference substance (positive control):
EC50 of the reference substance 3.5 -dichlorophenol is in the range 5 – 10 mg/L
Validity criteria fulfilled:
yes
Conclusions:
In a study, the substance showed 2.0 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/l according to the OECD guideline 209 (Currenta, 2009). An EC10 and an EC50 of >1000 mg/l were obtained in this tes
Executive summary:

In a study, the substance showed 2.0 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/l according to the OECD guideline 209 (Currenta, 2009). An EC10 and an EC50 of >1000 mg/l were obtained in this test.

Description of key information

In a study, the substance showed 2.0 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/l according to the OECD guideline 209 (Currenta, 2009). An EC10 and an EC50 of >1000 mg/l were obtained in this test.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

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