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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:
From 2016-05-27 to 2016-07-12
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL- Source and lot/batch No.of test material:6-MWC-149-1- Expiration date of the lot/batch:2018-02-08- Purity test date:2015-02-10STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL- Storage condition of test material: hygroscopic, refrigerator, under inert atmosphereTREATMENT OF TEST MATERIAL PRIOR TO TESTING: no- Treatment of test material prior to testing:- Preliminary purification step (if any):- Final dilution of a dissolved solid, stock liquid or gel:- Final preparation of a solid:
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Laboratory culture: /- Name and location of sewage treatment plant where inoculum was collected:Municipal sewage treatment plant of 31137 Hildesheim, Germany- Method of cultivation: /- Preparation of inoculum for exposure/pretreatment: the sludge was washed twice with chlorine free tap water and adjusted to a dry sludge concentration of 3.0 g/L+/- 10%. The sludge was used within 24H after sampling.- Initial biomass concentration: dry sludge concentration: 3.04 g/L corresponding to 1.52 g/L in the test vessel
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
Nominal: 18-22°C, actual: 20.6°C
pH:
The pH value of the activated sludge was determined prior to test start: 7.36. The pH value of the synthetic waste water was determined prior to use.pH was not adjusted prior to the definite study: 7.29.
Dissolved oxygen:
Permanent aeration to keep the dissolved oxygen concentration above 60-70% saturation and to maintain the sludge flakes in suspension.
Nominal and measured concentrations:
Nominal concentrations: 0.1 - 0.56 - 3.2 - 18 - 100 mg/L
Details on test conditions:
TEST SYSTEM- Test vessel: 1000 mL Erlenmeyer flasks, DIN 12380- Type (delete if not applicable): open - Material, size, headspace, fill volume: volume of the test medium: 500 mL- Aeration:permanent- No. of vessels per concentration (replicates): 5- No. of vessels per control (replicates):6- No. of vessels per reference control (replicates):3- Sludge concentration (weight of dry solids per volume):3.0 g/L- Nutrients provided for bacteria: no- Nitrification inhibitor used (delete if not applicable): none / N-allylthiourea noTEST MEDIUM / WATER PARAMETERS- Source/preparation of dilution water: synthetic waste water according to OECD 209- Particulate matter:/OTHER TEST CONDITIONS- Adjustment of pH: no- Photoperiod:/- Light intensity:/EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :TEST CONCENTRATIONS- Spacing factor for test concentrations:5.6- Justification for using fewer concentrations than requested by guideline:/- Range finding study- Test concentrations: 1) 1-10-100-500-1000 mg/L; 2) 0.1-5-100 mg/L- Results used to determine the conditions for the definitive study:yes; as the inhibition of heterotrophic respiration and nitrification were in the same range, therefore no indication for the requirement to measure the inhibition of nitrification in the definitive study was observed.
Reference substance (positive control):
yes
Remarks:
Copper (II) sulphate pentahydrate p.a.
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
0.25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
3.75 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: /- Effect concentrations exceeding solubility of substance in test medium:no- Adsorption (e.g. of test material to the walls of the test container):/- Blank controls oxygen uptake rate:specific respiration rates of the control: 20.1 (mean value of 6 replicates) mg O2/g.h
Results with reference substance (positive control):
- Reference item oxygen uptake rate: respiration rates of the control: at 58 mg/L: 24-23.2-23.2 mg O2/L.h, at 100 mg/L: 15.6-17.2-14.8 mg O2/L.h; 180 mg/L: 6.4-5.6-5.6 mg O2/L.h, corresponding to 23, 48 and 81% inhibition of respirationEC50= 100 mg/LThis is in the recommended range of validity of 53-155 mg/L- Results with reference substance valid? yes

The NOEC could not be determined.

Validity criteria:

The mean specific oxygen uptake rate of the control replicated was 20.1 mg O2/g.h (validity criterion: should be >=20). The oxygen uptake of the activated sludge from municipal treatment plant is influenced by seasonal fluctuations and fluctuations in sewage flow. etc. The lower oxygen uptake rate of 3 replicates reflects the range of common uptake rates of activated sludge from municipal treatment plants ans was considered to have no impact on quality and integrity of the study. Therefore, no impact on the results of the test item can be expected through lower respiration.

The coefficient of variation of the oxygen uptake rates in the control replicates was 3.7% (validity criterion: <30%)

Validity criteria fulfilled:
yes
Conclusions:
EC10= 0.25 mg/LEC50=3.75 mg/L
Executive summary:

The test item was tested in an OECD 209 and GLP to determine its toxicity towards respiration of an activated sludge. All the validity criteria were fulfilled. The EC10 of the test item was 0.25 mg/L and the EC50 was 3.75 mg/L.

Description of key information

The test item was tested in an OECD 209 and GLP to determine its toxicity towards respiration of an activated sludge. All the validity criteria were fulfilled. The EC10 of the test item was 0.25 mg/L and the EC50 was 3.75 mg/L.

Key value for chemical safety assessment

EC50 or LC50 for microorganisms:
3.75 mg/L
EC10, LC10 or NOEC for microorganisms:
0.25 mg/L

Additional information