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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
1984
Deviations:
not specified
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct dispersion in water
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): not reported
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Laboratory culture: The sample was maintained at 21°C with continuous aeration and used on the day of collection
- Name and location of sewage treatment plant where inoculum was collected: Severn Trent Water PLC Sewage Treatment Plant Belper. Debyshire
- Preparation of inoculum for exposure: The pH of the sample was 7.0 and the suspended soils equal 3.9 g/L prior to use
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Nominal and measured concentrations:
blank control, positive control, and nominal 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Aeration: yes
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 2
- Sludge concentration (weight of dry solids per volume): 3.9 g/L


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Spacing factor for test concentrations: limit test
- Justification for using fewer concentrations than requested by guideline: limit test
- Range finding study
- Test concentrations: 100 and 1000 mg/L, no adverse effects observed
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Key result
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
Details on results:
- Effect concentrations exceeding solubility of substance in test medium: yes
- Blank controls oxygen uptake rate: 0.71 and 0.66 mg O2/L/min
- Coefficient of variation of oxygen uptake rate in control replicates: 4%
Validity criteria fulfilled:
yes
Conclusions:
EC50 > 1000 mg/L
Executive summary:

In the activated sludge respiration inhibition study from Mead (1995) with Isonox 232, the EC50 for respiration inhibition was determined in a limit test to be > 1000 mg/L. Doseverification analysis was not performed. The study is considered reliable with restrictions for the risk assessment.

Description of key information

EC50 > 1000 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

In the activated sludge respiration inhibition study from Mead (1995) with Isonox 232, the EC50 for respiration inhibition was determined in a limit test to be > 1000 mg/L. Doseverification analysis was not performed. The study is considered reliable with restrictions for the risk assessment.