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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:
October 1989
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed according to the guideline.
Qualifier:
according to
Guideline:
other: EEC L 133, p. 118-122
Deviations:
yes
Remarks:
Instead a centrifuged sludge a settled sludge was used.
Principles of method if other than guideline:
The inhibitions were calculated on the basis of the measured time depend oxygen consumption of a Blank and Test solution.
GLP compliance:
yes
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
activated sludge
Details on inoculum:
Test system : Activated sludge collected from the sewage treatment plant of CH-4106 Therwil on 16/10/89. The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation.
Test type:
static
Water media type:
freshwater
Total exposure duration:
3 h
Test temperature:
20 ± 2°C
Nominal and measured concentrations:
TEST CONCENTRATIONS
- Test concentrations:
Reference substance : 32, 10 and 3.2 mg/l
Test substance : 100.58, 32.19, 10.1, 3.22 and 1.01 mg/L
The sludge concentration in the test bottles was 1.5 g/L.
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 ml BOD flasks with gas inlet
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dechlorinated drinking water

Measurements : Oxygen consumption per hour in mg/liter with a ORION - Electrode Type 97-08, ORION Microprocessor lonalizer 901 and
plotted on a recorder.
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
15 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: Graphically determined
Duration:
3 h
Dose descriptor:
other: IC20
Effect conc.:
3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: Graphically determined
Duration:
3 h
Dose descriptor:
other: IC80
Effect conc.:
78 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: Graphically determined
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
12 mg/L
Nominal / measured:
nominal
Conc. based on:
other: reference substance
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: Graphically determined
Details on results:
The inhibitions were calculated on the basis of the measured time depend oxygen consumption of a Blank and Test solution.
Validity criteria fulfilled:
not specified
Conclusions:
Toxicity studies to determine the inhibitory concentration of test substance on the respiration of aerobic waste water bacteria were conducted according to EEC L 133, p. 118-122 (30. May 1988) guideline. The test was conducted on activated sludge from a sewage treatment plant for 3 hours at 20°C. The results were graphically determined based on nominal concentrations and IC50 was determined to be 15 mg/L
Executive summary:

Toxicity studies to determine the inhibitory concentration of test material on the respiration of aerobic waste water bacteria were conducted according to EEC L 133, p. 118-122 (30. May 1988) guideline. The test was conducted on activated sludge from a sewage treatment plant for 3 hours at 20°C. The results were graphically determined . Activated sludge collected from the sewage treatment plant of CH-4106 Therwil on 16/10/89. The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation. 3,5-Dichlorophenol was used as referance substance. The effect concentration (IC50) was determined to be 15 mg/l , Test substance can be concluded to have moderate toxicity on microorganisms.

Description of key information

Toxicity to microorganism:

Toxicity studies to determine the inhibitory concentration of test material on the respiration of aerobic waste water bacteria were conducted according to EEC L 133, p. 118-122 (30. May 1988) guideline. The test was conducted on activated sludge from a sewage treatment plant for 3 hours at 20°C. The results were graphically determined . Activated sludge collected from the sewage treatment plant of CH-4106 Therwil on 16/10/89. The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation. 3,5-Dichlorophenol was used as referance substance. The effect concentration (IC50) was determined to be 15 mg/l , Test substance can be concluded to have moderate toxicity on microorganisms.

Key value for chemical safety assessment

EC50 for microorganisms:
15 mg/L

Additional information

Toxicity to microorganism:

Toxicity of test material on microorganism was evaluated using two experimental reports described as follows:

In the first toxicity studies to determine the inhibitory concentration of test material on the respiration of aerobic waste water bacteria were conducted according to EEC L 133, p. 118-122 (30. May 1988) guideline. The test was conducted on activated sludge from a sewage treatment plant for 3 hours at 20°C. The results were graphically determined . Activated sludge collected from the sewage treatment plant of CH-4106 Therwil on 16/10/89. The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation. 3,5-Dichlorophenol was used as referance substance. The effect concentration (IC50) was determined to be 15 mg/l , Test substance can be concluded to have moderate toxicity on microorganisms.

Similarly in the second study Respiratory inhibition study ofactivated sludge by test material was conducted according to EC Directive 88/302/EEC - activated sludge: verificationof the inhibition of respiration;corresponds to the OECD Guidelines for Testing of Chemicals 209 and ISO Standard 8192.In the short-term respiration test, the effect of test substance on the respiration of aerobicMicroorganisms (activated sludge) after a short exposure time (30 to 180 min) were investigated.As the test result, the effective concentrations are determined, in which the breathinginhibited relative to a reference value without Priifsubstanz by 20, 50 and 80% (EC20,EC50, EC80).  Effect of the test substance on the respiration of municipal activated sludge were found asEC20: after 30 min about 40 mg / l ,EC50: - After 30 min> 1000 mg / l