Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
19 Nov 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1999
Report Date:
1999

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
adopted 1984
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 05, 1988.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): AEF122006 Technical

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Preparation of inoculum for exposure: The sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. The latter procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (g) to its dry weight (g) determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 4 g dry material per litre, were made up with tap water. To this mixture, 50 mL synthetic sewage feed (see below) per litre was added daily, starting three days prior to use, and the sludge was kept at room temperature under continuous aeration until use. Immediately before use, the dry weight of the activated sludge was determined, and diluted to 4 g/L with tap water. The pH of the activated sludge was measured to be pH 7.3.

Study design

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

Test conditions

Test temperature:
18 - 19 °C
pH:
Test start: 7.0 - 7.3
Test end: 8.1
Dissolved oxygen:
Test start: 7.5 - 8.3 mg/L
Test end: 6.8 - 7.6 mg/L
Nominal and measured concentrations:
Nominal: 10, 32, 100, 320, 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: for incubation: glass flasks 1 L; for measurement of respiration: Karlsruher flasks 250 mL
- Material, fill volume: glass, 500 mL
- Aeration: compressed air at an air flow rate of 0.6 L/min
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: 4 g dry sewage material per litre

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The oxygen concentrations were determined before test start and at the end of the incubation period in all test concentrations and controls.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: approx. 3.2
- Test concentrations: 10, 32, 100, 320, 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol

Results and discussion

Effect concentrations
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: EC50 was calculated to be 6 mg/L

Any other information on results incl. tables

In comparison to the inoculum controls, the respiration rate of the activated sludge was not inhibited (-0.5 to -19.0%) at the four lowest concentrations of nominal 10 to 320 mg/L. At the highest concentration of nominal 1000 mg/L, the respiration rate was moderately inhibited by 12.7%. Test substance concentrations exceeding 1000 mg/L nominal were not tested.

From these inhibition rates, the 3 h EC20 and the 3 h EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 20% inhibition was noted after three hours exposure time. Nevertheless, the 3 h EC20 and EC50 are far above 1000 mg/L nominal under the present test conditions.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes