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activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: according to EC Directive 92/69/EEC and Regulation EC/440/2008 guideline methods under GLP conditions
according to guideline
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
Details on sampling:
At the end of the 3 hour incubation, a portion of the first test mixture was transferred to
fill a clean 250 mL (nominal volume) sample bottle containing a PTFE-coated stirrer bar.
The DO probe was inserted in the sample bottle, taking care to avoid trapping air bubbles
against the probe membrane. The probe was sealed against the bottle-neck to ensure that
the sample could not become re-oxygenated by contact with the atmosphere.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Preparation and Maintenance of the Inoculum
The inocula used in this study were not acclimatised or adapted to the test item before exposure to the test substance under test conditions. The inocula were maintained by aeration at all times and were fed overnight with synthetic sewage at a rate of 50 mL/L during the intervals between preparation and final use.
Test type:
Water media type:
Total exposure duration:
3 h
Test temperature:
21 °C
3 h
Dose descriptor:
Effect conc.:
> 1 000 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
respiration rate
Details on results:
In the definitive (limit) test five replicates were employed, each containing the test item at a concentration of 1000 mg/L. The purpose of this test was firstly to assess the reproducibility with a greater number of replicates, and secondly to show that the EC50 of the test substance was less than 1000 mg/L. The results of the definitive (limit) assessment are presented in Table 3.
As in previous tests, the reproducibility was poor with results ranging from 26 % enhancement to 47% inhibition. The maximum level of inhibition observed was 47%, therefore based on the results of this test, it is concluded that the EC50 of 2,4,7,9-tetramethyldecane-4,7-diol is greater than 1000 mg/L.
Results with reference substance (positive control):
The EC50 for 3,5-DCP was estimated from a plot of the results to be 5.92 mg/L.
Validity criteria fulfilled:
The 3-hour EC50 for sludge respiration inhibition by 2,4,7,9-tetramethyldecane-4,7-diol is greater than 1000 mg/L.

Executive summary:

The 3-hour EC50 for sludge respiration inhibition by 2,4,7,9-tetramethyldecane-4,7-diol is greater than 1000 mg/L.

Description of key information

The 3-hour EC50 for sludge respiration inhibition by 2,4,7,9-tetramethyldecane-4,7 -diol is greater than 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information