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Ecotoxicological information

Toxicity to microorganisms

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Link to relevant study record(s)

Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-09-10 to 2013-09-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
Adopted July 22 2010
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test concentrations were prepared separately by adding the respective amount of test item to the test vessel. The substance was mixed with demineralised water and stirred overnight.
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): Small brown particles sedimented on the bottom of the test vessels.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Name and location of sewage treatment plant where inoculum was collected: Municipal sewage treatment plant of Hildesheim, Germany receiving predominantly municipal sewage.
- Pretreatment: The sludge was washed twice with tap water and adjusted to a dry sludge concentration of 3.0 g/L ± 10%
- Initial biomass concentration: 3.13 g/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21 °C
pH:
7.14 - 7.18
Nominal and measured concentrations:
Nominal test substance concentrations: 1.0, 3.2, 10, 32, 100, 320 and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks (nominal volume 500 mL)
- Material, fill volume: glass, 500 mL
- Aeration: continuous
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 6
- Sludge concentration (weight of dry solids per volume): 1.57 g/L
- Nutrients provided for bacteria: synthetic wastewater (16 mL)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: demineralised water

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): oxygen uptake

TEST CONCENTRATIONS
- Range finding study: yes, two preliminary tests
- Test concentrations: 10, 100, 1000 mg/L
- Results used to determine the conditions for the definitive study: Inhibition of > 50% was observed at test 1000 mg/L.
Reference substance (positive control):
yes
Remarks:
copper (II) sulphate pentahydrate
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
3.2 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:
EC10
Effect conc.:
5.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: confidence interval: 4.41 - 6.55 mg/L
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
263 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: confidence interval: 222 - 313 mg/L
Details on results:
- Blank controls oxygen uptake rate: 30.5 mg O2/g*h
Results with reference substance (positive control):
EC50 (3 h): 95.9 mg/L (95% Confidence Interval: 89.5 - 103 mg/L)
Reported statistics and error estimates:
The NOEC was determined by calculation of statistical significance of the inhibition of respiration in comparison to the control. One Way Analysis of Variance (ANOVA) and DUNNETT's test was used for NOEC calculations. When running a One Way Analysis of Variance a Normality test and an Equal Variance test were done first. The ECx-values of the test item and the reference item were calculated by sigmoidal dose-response regression and linear regression, respectively, using software GraphPadPrism.
Validity criteria fulfilled:
yes
Conclusions:
The study resulted in an EC10 (3 h) of 5.4 mg/L and a NOEC (3 h) of 3.2 mg/L based on inhibition of respiration of activated sludge microorganisms.

Description of key information

EC10 (3 h): 5.4 mg/L (nominal, OECD 209)

NOEC (3 h): 3.2 mg/L (nominal, OECD 209)

EC50 (3 h): 263 mg/L (nominal, OECD 209)

Key value for chemical safety assessment

EC50 for microorganisms:
263 mg/L
EC10 or NOEC for microorganisms:
3.2 mg/L

Additional information

The toxicity of the substance to activated sludge microorganisms was tested according to OECD guideline 209. The respiration rate of activated sludge at nominal test substance concentrations of 1.0, 3.2, 10, 32, 100, 320 and 1000 mg/L was determined after 3 h of incubation. Inhibition of microbial respiration was recorded resulting in an EC10 (3 h) of 5.4 mg/L a NOEC (3 h) of 3.2 mg/L and an EC50 (3 h) of 263 mg/L.