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activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
April 2017 - May 2017
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP-compliant, guideline study, available as an unpublished report, toxicity control for a biodegradation study, acceptable with restrictions
Reason / purpose for cross-reference:
reference to same study
Principles of method if other than guideline:
Toxicity control used in OECD No. 301B "Ready biodegradability: CO2 Evolution Test.
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Physical state/Appearance: white solid
Batch: 80100005
Purity: 99.80%
Expiry Date: 13 October 2018
Storage Conditions: room temperature in the dark
Analytical monitoring:
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 24 April 2017 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.
Preparation of the inoculum:
The activated sewage sludge sample was washed twice by settlement and re-suspension in mineral medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. The washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC and used on the day of collection. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the washed activated sewage sludge by suction through pre-weighed GF/A filter paper* using a Buchner funnel. Filtration was then continued for a further 3 minutes after rinsing the filter three successive times with 10 mL of deionized reverse osmosis water. The filter paper was then dried in an oven at approximately 105 ºC for at least 1 hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 2.8 g/L prior to use.
Test type:
other: Toxicity control used in the biodegradation test (OECD TG 301).
Total exposure duration:
28 d
Nominal and measured concentrations:
An aliquot (143 mL) of the test item stock solution (100 mg test item/L) was dispersed in inoculated mineral medium along with an aliquot (51.4 mL) of the sodium benzoate stock solution. The volume was adjusted to 3 liters to give a final concentration of 14.3 mg test item/L plus 17.1 mg sodium benzoate/L, equivalent to a total of 20 mg carbon/L.
28 d
Dose descriptor:
Effect conc.:
14.3 mg/L
Nominal / measured:
Conc. based on:
test mat.
Validity criteria fulfilled:
not applicable
No toxicity was observed with a concentration of 14.7 mg/L test item.
Executive summary:

The results were obtained from a toxicity control carried out as part of an OECD 301B Modified sturm test. The test item did not exhibit any inhibitory effects on the microbial inoculum.

Description of key information

The results are taken from a toxicity control carried out as part of an OECD 301B Modified sturm test. The test item did not appear to exhibit any inhibitory effects on the microbial inoculum.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
14.7 mg/L

Additional information