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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:
2016-06-03 to 2016-12-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Version / remarks:
22 July 2010
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
30 May 2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Appropriate amounts of test item were directly weight into the test vessels and test water was added. The composition was stirred intensively
- Controls: pure water, synthetic sewage and inoculum, but without addition of test item
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Test System: Activated sludge
Origin: Pool Sewage Treatment Works (West Yorkshire, U.K.)
Reason for the selection: Predominantly domestic catchment
Pretreatment: The sludge was transported to the test facility in a closed container with an adequate headspace to prevent the sample becoming anoxic. On arrival at the test facility, the sludge was aerated
with a compressed air supply delivered through a suitable distribution device. The suspended solids concentration was determined gravimetrically following homogenisation and adjusted using
dechlorinated tap water to 3 g/L (± 0.3 g/L). The sludge was maintained at 20 ± 2°C with aeration. During storage it was maintained at 20 ± 2°C and fed with synthetic sewage concentrate at a
rate of 50 mL/L.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
20.4°C
pH:
control: 7.01 to 7.37
test item: 7.13 to 7.44
Nominal and measured concentrations:
test item: 1, 10, 100 and 1000 mg/L
positive control: 0.1, 2.0 and 40 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL glass conical flasks
- Type: open
- Aeration: yes
- No. of vessels per test item concentration (replicates): 3
- No. of vessels per positive control concentration (replicates): 1
- No. of vessels of control (replicates): 4
- Sludge concentration (weight of dry solids per volume): 3 g/L
- Nitrification inhibitor used: N-allylthiourea

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



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Test item concentrations: 1, 10, 100 and 1000 mg/L
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
Key result
Duration:
3 h
Dose descriptor:
NOEC
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):
3,5-Dichlorophenol
EC50 = 12 mg/L (total respiration)
Validity criteria fulfilled:
yes
Conclusions:
The test item had no inhibiting effects on the respiration rate of activated sludge up to and including 1000 mg/L.
The NOEC was determined to be 1000 mg /L. The 3-hour EC50 value exceeded 1000 mg/ and could not be established.
Executive summary:

The influence of the test item on the activity of activated sludge was evaluated by measuring the respiration rate under defined conditions according to the OECD Guideline for Testing of Chemicals, No. 209: "Activated Sludge, Respiration Inhibition Test", adopted July 22, 2010.

The test item had no inhibiting effects on the respiration rate of activated sludge up to and including 1000 mg/L.

The NOEC was determined to be 1000 mg /L. The 3-hour EC50 values exceeded 1000 mg/L and could not be established.

The positive control 3,5-Dichlorophenol was tested in the same way as the test item. The 3-hour EC50 for total respiration was found to be 12 mg/L thus lying in the range of 5 - 30 mg/L recommended by the test guidelines. The result confirms the suitability of the activated sludge used.

Description of key information

The test item had no inhibiting effects on the respiration rate of activated sludge up to and including 1000 mg/L.

The NOEC was determined to be 1000 mg /L. The 3-hour EC50 value exceeded 1000 mg/ and could not be established.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information