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Ecotoxicological information

Toxicity to microorganisms

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Link to relevant study record(s)

Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009
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)
Deviations:
no
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 +/- 2 °C, daily feed with synthetic medium
- 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:
19.6 °C (concerning the highest concentration of 1000 mg/l)

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

Dissolved oxygen:
oxygen (mg/l): O2-start 5.5; O2-end 2.9 (concerning the highest concentration of 1000 mg/l)

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)
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
Remarks:
(respiratory rates of the 2 controls differ less than 15 % from each other; the EC50 of the reference compound 3,5-dichlorophenol is in the range 5–30 mg/L)
Conclusions:
The test item showed 0 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L.
Executive summary:

In order to test the toxicity to microorganism of the substance, activated sludge from predominantly domestic sewage plant was exposed to three nominal concentrations of the substance (10, 100, 1000 mg/l) and to the solution with positive reference substance for a period of 3 hours. Dissolved oxygen was recorded and respiration rates were calculated. 0 % respiration inhibition was observed at the highest concentration of test substance. This toxicity study is classified as acceptable and satisfies the guideline requirements for the toxicity study to microorganisms according to the OECD guideline 209.

Description of key information

The substance showed 0 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L according to the OECD guideline 209. The EC50 is higher 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

"Should read: > 1000 mg/L"

In order to test the toxicity to microorganism of the substance, activated sludge from predominantly domestic sewage plant was exposed to three nominal concentrations of the substance (10, 100, 1000 mg/l) and to the solution with positive reference substance for a period of 3 hours. Dissolved oxygen was recorded and respiration rates were calculated. 0 % respiration inhibition was observed at the highest concentration of test substance. This toxicity study is classified as acceptable and satisfies the guideline requirements for the toxicity study to microorganisms according to the OECD guideline 209.