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activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-07-01 to: 2002-07-12
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
other: Commission Directive 88/302/EEC
equivalent or similar to guideline
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
Analytical monitoring:
Details on sampling:
no data
Details on test solutions:
The test substance was added to about 130 mL of deionized water and stirred overnight before testing (equilibration phase)
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
no data
Test type:
not specified
Water media type:
not specified
Limit test:
Total exposure duration:
3 h
Remarks on exposure duration:
permanent aeration
Post exposure observation period:
no data
no data
Test temperature:
20 +/- 2 °C
pH of the suspension before application : 6.1
pH of the various test substance concentratoins: 7.2 - 7.4
Dissolved oxygen:
no data
Nominal and measured concentrations:
Nominal test concentrations (mg/L): 1000, 1800, 3200, 5600, 10000
Details on test conditions:
- Test vessel: aeration tank of waste water treatment plant treating predominately domestic sewage (Wupper area water authority)
- Test concentration of the activated sludge : 480 mg/L suspended solids
Reference substance (positive control):
3,5-Dichlorophenol (purity of 97%)
3 h
Dose descriptor:
Effect conc.:
> 10 000 mg/L
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
respiration rate
Details on results:
- Tungsten trioxide showed 3.1 % respiration inhibition of activated sludge at a test substance concentration of 10,000 mg/L.
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 6.1 mg/L
Reported statistics and error estimates:
- The EC values were determined by statistical methods (probit analysis)

Test concentration: 1000 mg/L - Inhibition: 0.0% Test Concentration: 1800 mg/L - Inhibition: 15.4% Test Concentration: 3200 mg/L - Inhibition: 7.7% Test Concentration: 5600 mg/L - Inhibition: 7.7% Test Concentration: 10000 mg/L - Inhibition: 3.1% Physical-Chemical oxygen consumption was 0 mg/L-h for all test concentrations. The Respiratory rate-phsical-chemical oxygen consumption ranged from 22.0 mg/L-h to 27.0 mg/L-h

Tungsten trioxide showed 3.1% respiration inhibition of activated sludge at the test substance concentration of 10,000 mg/L. The EC50 > 10,000 mg/L

Description of key information

Tungsten trioxide was tested for toxicity to microorganisms. Tungsten trioxide showed 3.1% respiration inhibition of activated sludge at the test substance concentration of 10,000 mg/L. The EC50 > 10,000 mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
10 000 mg/L

Additional information