Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to
Guideline:
other: Commission Directive 87/302/EEC: "Activated Sludge Respiration Inhibition Test", Official Journal of the European Communities No. L 133/118-122, dated May 30, 1988
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Details on test material:
Purity: 99.2%

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
yes
Remarks:
Tap water

Test organisms

Test organisms (species):
activated sludge, domestic

Study design

Total exposure duration:
3 h

Test conditions

Test temperature:
21 to 22°C during incubation time
19 to 22°C during measurement
pH:
7.4 to 8.6
Dissolved oxygen:
The concentration of dissolved oxygen did not drop below 2.5 mg/L during the incubation period, and just before the measurements of the respiration rates the oxygen concentrations were at least 8.4 mg/L.
Nominal and measured concentrations:
Nominal: 1, 3.2, 10, 32 and 100 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol

Results and discussion

Effect concentrations
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: Highest dose tested

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
3-hr EC50: >100 mg/L (highest concentration tested)
Executive summary:

The effects of the test substance on activated sludge were determined in a 3-hour exposure laboratory study conducted under OECD Guideline 209 and Commission Directive 87/302/EEC. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test substance after an incubation period of 3 hours. Test concentrations: 100.0, 32.0, 10.0, 3.2 and 1.0 mg/L; 32.0, 10.0 and 3.2 mg 3,5-dichlorophenol/L and two inoculum controls.

The test substance had negligible effects on the respiration of activated sludge microorganisms. In comparison to the inoculum controls the respiration rate of the activated sludge was inhibited by 1.6% at the highest tested concentration of 100 mg the test substance/L. The 3-hour EC20 and EC50 could not be determined, however they are clearly higher than 100 mg/L under the present test conditions. The 3-hour EC50 for the positive control 3,5-dichlorophenol, which was tested in the same way as the test substance, was found to be 16.2 mg/L and is within the range of 5-30 mg/L recommended by the test guidelines; thus, confirming suitability of the activated sludge.

The test substance exhibited no acute toxic effects to activated sludge at 100 mg/L, the highest concentration tested. The EC20 and EC50 values could not be determined due to the lack of any inhibitory effect of the test substance, however they can be assumed to be >100 mg/L. Therefore, it can be concluded that the test substance poses a very low risk to the activated sludge of a sewage treatment plant.