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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:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
not required
Vehicle:
no
Remarks:
Not applicable
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: 'Waterschap Aa en Maas',
's- Hertogenbosch, The Netherlands, receiving predominantly
domestic sewage.:
- Preparation of inoculum for exposure:The sludge was coarsely sieved (1 mm) and allowed to settle.The supernatant was removed and ISO-medium was added. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (3.0 g/L of sludge, as used for the test). The pH was 7.8 on the day of testing. The batch of sludge was used one day after collection; therefore 50 mL of synthetic medium (=sewage feed) was
added per litre of activated sludge at the end of the collectionday. The sludge was kept aerated at test temperature until use.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Remarks on exposure duration:
Contact time
Post exposure observation period:
Not applicable
Test temperature:
20- 21°C
pH:
7.0 - 8.2
Nominal and measured concentrations:
Nominal
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass
- Type: Open
- Material, size, headspace, fill volume: Glass, 1L, yes, 500mL
- Aeration: yes
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 6
- No. of vessels per abiotic control (replicates): 1
- Sludge concentration (weight of dry solids per volume): 3.0g/L
- Nutrients provided for bacteria: synthetic medium

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:Adjusted ISO-medium, formulated using RO-water (tap water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) with the following composition:
CaCl2.2H2O 211.5 mg/L
MgSO4.7H2O 88.8 mg/L
NaHCO3 46.7 mg/L
KCl 4.2 mg/L

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not applicable
- Justification for using fewer concentrations than requested by guideline: not applicable, limit test
- Test concentrations: 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
other: NOELR
Remarks:
loading rate
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels:
- Other:
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this present test the test substance was not toxic to waste water bacteria (activated sludge) at a loading rate of 1000 mg/L (NOELR).
The ELR50 was above 1000 mg/L.

Description of key information

In a GLP-compliant, OECD guideline study conducted with the test substance no toxicity was seen at the highest tested concentration (1000 mg/L). The ELR50 was determined to be >1000mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

It is not appropriate to include an EC50 value for the chemical safety assessment above as this is determined to be greater than the highest concentration tested