Registration Dossier

Diss Factsheets

Administrative data

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

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
N-acetylhexanelactam
EC Number:
217-565-6
EC Name:
N-acetylhexanelactam
Cas Number:
1888-91-1
Molecular formula:
C8H13NO2
IUPAC Name:
N-acetylhexanelactam

Sampling and analysis

Analytical monitoring:
no

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
lnoculum Activated sludge from the aeration tank of a municipal biological waste water treatment plant, not adapted, not pre-conditioned
Concentration 1.6 g/l dry matter in the final mixture
Source (Date; Time) ARA Werdhölzli, CH-8048Zürich (31 January 2003; 2.00 p.m.)
1.6 g/l dry matter

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h

Test conditions

Test temperature:
22 ±.0.5"C
Details on test conditions:
1000 ml flasks containing a total volume of test suspension of 500 ml; aerated by shaking (120 r.p.m.) Measuring apparatus: 300 ml flat bottom BOD flask; polarographic oxygen electrode, connected to a potentiometric recorder

Synthetic sewage feed prepared with tap water:16 ml of 100-fold sewage concentrate per 500 ml of final test mixture

Controls: 2 blank controls with inoculated sample without test substance

The oxygen concentration, in mg/|, was measured with a oxygen electrode (ORION 9708) inserted to a 300 ml BOD bottle and recorded for about 5 to 10 min.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol

Results and discussion

Effect concentrationsopen allclose all
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Duration:
3 h
Dose descriptor:
other: EC20 / EC50 / EC80
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
At 100 mg/L the test substance showed no significant toxic effects to the activated sludge. The respiration rate was in the same range as determined for the two blank controls.
Results with reference substance (positive control):
The EC50 value of the reference substance 3,S-dichlorophenol was estimated to be 4.7 mg/L which was low but in the range of 5 mg/l thus confirming suitability of activated sludge and test conditions. The
variation between the two controls was ± 2.1 %. Therefore, the test was considered valid.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The toxicity to activated sludge of the registration substance was tested in a study according to OECD209 resulting in a NOEC (3h) of 100 mg/L and a EC20 / 50 / 80 (3h)>100mg/L.
Executive summary:

The inhibitory effect of the test substance on the oxygen consumption of activated sludge microorganisms of a municipal sewage treatment plant was investigated under aerobic static conditions. The inhibitory effect may include the effect on respiration and nitrification. The exposure time of the test substance on the activated sludge was 3 hours.

This study represents a limit test. The only nominal concentrations of the test substance was 100 mg/L.

This test concentration was prepared by direct addition.

For the estimation of the effective concentration leading to 20, 50, and 80 % respiration inhibition (EC20, EC50, EC80) the nominal content of the test substance was used, assuming the test compound to be stable in water over 3 h.

At 100 mg/L the test substance showed no significant toxic effects to the activated sludge. The respiration rate was in the same range as determined for the two blank controls.

Based on these data the EC20, EC50, EC80 values of the test substance were estimated to be >100 mg/L.