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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
Study period:
03.05.2017-23.05.2017
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))
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Details on sampling:
No analysis was carried out to determine the homogeneity, concentration or stability of the test item formulation. This exception is considered not to affect the purpose or integrity of the study.
Vehicle:
not specified
Test organisms (species):
activated sludge, domestic
Details on inoculum:
A mixed population of activated sewage sludge micro-organisms was obtained on 3 April 2017 for the range-finding test and on 22 May 2017 for the definitive test from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK which treats predominantly domestic sewage.
Test type:
static
Water media type:
other: The test water used for the range-finding and definitive tests was deionized reverse osmosis water containing less than 1 mg/L Dissolved Organic Carbon (DOC).
Limit test:
no
Total exposure duration:
30 min
Post exposure observation period:
na
Test temperature:
21C
pH:
7.5-8
Dissolved oxygen:
5.4-6.7 mg/L
Nominal and measured concentrations:
Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 180, 320, 560, 1000 and 1800 mg/L.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
770 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
The reference item gave a 3-Hour EC50 value of 5.3 mg/L, 95% confidence limits 3.8 to 7.3 mg/L.
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of 770 mg/L.
Executive summary:

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2010) No. 209 "Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)".

Following a preliminary range-finding test, activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 180, 320, 560, 1000 and 1800 mg/L (3 replicates) for a period of 3 hours at measured temperatures of approximately 22 °C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of 770 mg/L.

The reference item gave a 3-Hour EC50 value of 5.3 mg/L, 95% confidence limits 3.8 to 7.3 mg/L.

Description of key information

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2010) No. 209 "Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)".

Following a preliminary range-finding test, activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 180, 320, 560, 1000 and 1800 mg/L (3 replicates) for a period of 3 hours at measured temperatures of approximately 22 °C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of 770 mg/L.

The reference item gave a 3-Hour EC50 value of 5.3 mg/L, 95% confidence limits 3.8 to 7.3 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
770 mg/L

Additional information