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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:
2002-07-01 to 2002-07-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented, scientifically sound study that was conducted in accordance with GLP and the Commission Directive 88/302/EEC. The test method was similar to OECD guideline 209. However, there were no details on the testing conditions.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Qualifier:
according to guideline
Guideline:
other: Commission Directive 88/302/EEC; Official Journal of the EC L133 Part C (1988)
Principles of method if other than guideline:
The method assesses the effect of a test substance on microorganisms by measuring the respiration rate under defined conditions in the presence of different concentrations of the test substance.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Details on sampling:
- Concentrations: Test concentration of the activated sludge 360.0 mg/L suspended solids
- Sampling method: Direct weighing
Vehicle:
yes
Details on test solutions:
The test substance was added to about 130 mL deionized water and stirred overnight before testing (equilibration phase).
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Origin: aeration tank of waste water treatment plant treating predominantly domestic sewage (Wupper area water authority)
- Pretreatment: aeration of the activated sludge; daily feed with synthetic medium
Test type:
other: mixed population of aquatic organisms (activated sludge)
Water media type:
not specified
Limit test:
yes
Total exposure duration:
3 h
Remarks on exposure duration:
3 hours with permanent aeration
Post exposure observation period:
no data
Hardness:
no data
Test temperature:
20 +/- 2 °C
pH:
pH of the suspension before application: 7.1
7.4 - 7.6
Dissolved oxygen:
5.6 - 6.2
Salinity:
n/a
Nominal and measured concentrations:
Nominal concentrations: 100, 1000, 10000 mg/L
Details on test conditions:
no data
Reference substance (positive control):
yes
Remarks:
3.5-Dichlorophenol, mg/L
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The test substance showed a 17.5% respiration inhibition of activated sludge at a test substance concentration of 10000 mg/L.
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: See results below
Reported statistics and error estimates:
no data

Measured values of reference substance

  Test concentration (mg/L)  O2 start (mg O2/L)  O2 end (mg O2/L  Exposure time (min)  Temp. (C)  pH 
Reference  6.4  4.8  20  7.7 
substance  10  8.4  8.0  20  7.6 
3.5 -Dichloro-phenol  20  9.0  8.7  20  7.6 

Results for Reference Substance: 3.5 -Dichlorophenol

  Test Concentration Respiratory rate (mg/L.h)  Inhibition 
24.0  25.0 
10  8.0  75.0 
20  6.0  81.3 
Conclusions:
The method assessed the effect of a test substance on micoorganisms by measuring the respiration rate under defined conditions in the presence of different concentrations of the test substance. Ammonium paratungstate showed 17.5% respiration inhibition of activated sludge at a test substance concentration of 10000 mg/L. The EC50 > 10000 mg/L.

Description of key information

The method assessed the effect of a test substance on micoorganisms by measuring the respiration rate under defined conditions in the presence of different concentrations of the test substance. Ammonium paratungstate showed 17.5% respiration inhibition of activated sludge at a test substance concentration of 10000 mg/L. The EC50 > 10000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
10 000 mg/L

Additional information

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