Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-12-23 to 2003-05-12
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: OECD Guideline under GLP

Data source

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

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
87/302/EWG, C.11
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Since the test item hydrolyses in water very quickly, in the present test the hydrolysis products of the test item were tested, according to the draft guidance document on aquatic toxicity testing of difficult substances. Therefore, a concentrated stock solution of the test item was prepared by dosing 1000 mg test item into 200 mL deionised water. This stock solution was stirred for 24 hours. Thus, at the start of the test the main part of the test item were hydrolysis products.

Test organisms

Test organisms (species):
activated sludge, domestic
Details on inoculum:
-Origin: sewage plant Groß-Zimmern, Germany
-Cultivation: 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 3 g dry material per litre, were made up with tap water. To this mixture, 50 mL synthetic sewage feed per litre was added two 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 3 g/L with tap water. The pH of the activated sludge was determined to be pH 7.8.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
no

Test conditions

Hardness:
not given in the report
Test temperature:
19-20 °C
pH:
7.6-8.5
Dissolved oxygen:
7.3-7.8
Salinity:
not given in the report
Nominal and measured concentrations:
nominal: 10, 32, 100, 320, 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass flask with 1 litre volume and Karlsruher flasks of 250 mL volume
- Aeration: appr. 0.6 litre per minute with compressed air

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
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
Up to the highest nominal test concentration of 1000 mg/l less than 20 % inhibition was noted after 3 h incubation
Results with reference substance (positive control):
The 3-hour EC50 of 3,5-Dichlorophenol was calculated to be 14.1 mg/L .

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The test item was not toxic to bacteria from activated sludge under the reported conditions.
Executive summary:

The influence of the test item on the activity of activated sludge was evaluated by measuring the respiratory rate under defined conditions (OECD Guideline 209) . 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 item after an incubation period of 3 hours. Based on measured inibition rates, the 3 -hour EC20 and 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 incubation. Nevertheless the 3 -hour EC20 and EC50 are clearly higher than 1000 mg/L under the reported conditions.The positive and the inocculum control worked as expected.