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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
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
GLP compliance:
yes
Analytical monitoring:
yes
Vehicle:
yes
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
A mixed population of activated sewage sludge micro-organisms was obtained on 13 May 2016 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK which treats predominantly domestic sewage.
Test type:
semi-static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Reference substance (positive control):
yes
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
ca. 18 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Validity criteria fulfilled:
yes
Conclusions:
The No Observed Effect Concentration (NOEC) after 3 hours exposure was 18 mg/L.
Executive summary:

Introduction

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)".

Methods

Following a preliminary range-finding and initial experiment, activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 10, 18 and 32 mg/L (5 replicates) for a period of 3 hours at measured temperatures of between 20 and 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.

Results

The effect of the test item on the respiration of activated sewage sludge gave a No Observed Effect Concentration (NOEC) after 3 hours exposure of 18 mg/L.

The reference item gave a 3-Hour EC50 value of 6.6 mg/L, 95% confidence limits 4.9 to 8.9 mg/L.

Description of key information

The No Observed Effect Concentration (NOEC) after 3 hours exposure was 18 mg/L.

Key value for chemical safety assessment

Additional information

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