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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Chemical name of vehicle: Tween 80

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Laboratory culture: No, activated sludge from a municipal sewage treatment plant, Hildesheim
- Preparation of inoculum for exposure: washed twice with drinking water (dechlorinated)
- Initial biomass concentration: 2 g/L (dry weight) sludge
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21 °C
Nominal and measured concentrations:
Nominal test concentrations: Control, 100, 180, 320, 580, 1000 mg/L
Details on test conditions:
TEST SYSTEM
- No. of vessels per concentration : 1
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): 1


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic effluent according to Guideline
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
> 1 000 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:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: EC50 = 47 %

Table 1: Validity criteria for OECD 209.

Criterion from the guideline

Outcome

Validity criterion fulfilled

The blank controls (without the test substance or reference substance) oxygen uptake rate should not be less than 20 mg oxygen per one gram of activated sludge (dry weight of suspended solids) in an hour.

<28 mg/g*h

yes

The coefficient of variation of oxygen uptake rate in control replicates should not be more than 30% at the end of definitive test.

< 15%

yes

 

Validity criteria fulfilled:
yes
Remarks:
Please refer to table 1 in section "Any other information on results incl. tables"

Description of key information

The inhibition of the degradation activity of activated sludge is  not anticipated (EC10 > 1000 mg/L).

Key value for chemical safety assessment

Additional information

The toxicity of the substance to microorganisms was investigated in a study according to OECD 209. The test was conducted at nominal test concentrations of 100, 180, 320, 580 and 1000 mg/L. The respiration rate of activated sludge, taken from a municipal sewage treatment plant, was recorded for 3 hours. An inhibition of the respiration rate was not observed. The determined EC50 (3 h) was > 1000 mg/L.

Based on the available study results, the substance is not considered toxic to microorganisms.

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