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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
Study period:
1988-10-07-1988-11-08
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP guideline study. Deviations to the updated OECD Guideline (adopted 2010). The coefficient of analysis of the control was not reported.
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
adopted 1984
Deviations:
yes
Remarks:
See "Principles of method if other than guideline"
Principles of method if other than guideline:
Instead of a centrifuged sludge a settled sludge was used. The substance was tested at one concentration (100 mg/L) in duplicate samples.
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
The test substance was added directly to the test vessel.
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Activated sludge collected from the sewage treatment plant of CH - 4153 Reinach on 07/11/1988.
- The preparation was carried out according to the method described in the guideline. Except the settling instead of centrifuging.
- Initial biomass concentration: 1.8 g/L
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
20 ± 2 °C
Nominal and measured concentrations:
Nominal test concentrations: 102.5 and 107.0 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL BOD flasks with gas inlet
- Fill volume: 200 mL
- Aeration: none
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- Biomass loading rate: 1.8 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated drinking water

TEST CONCENTRATIONS
- Test concentrations: 102.5 and 107 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: IC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: IC80
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none reported
- Effect concentrations exceeding solubility of substance in test medium: none reported
Results with reference substance (positive control):
- Results with reference substance valid? YES
- Relevant effect levels: IC50 = 9 mg/L

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriate low concentrations. 

Key value for chemical safety assessment

Additional information

In a 3-hr acute toxicity study sewage sludge micro-organisms were exposed to the test item at nominal concentrations of 100 mg/L in accordance with OECD 209. The IC50 value based on respiration rate after was > 100 mg/L after a 3 h contact time.