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Toxicity to microorganisms

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toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
no guideline followed
Principles of method if other than guideline:
GLP compliance:
Specific details on test material used for the study:
Analytical monitoring:
not specified
Details on sampling:
No data
not specified
Details on test solutions:
No data
Test organisms (species):
activated sludge, domestic
Details on inoculum:
Bacteria used have to be isolated from sewage sludge. The original German document provided as an annex to this paper lists a number of gram positive and gram negative bacteria that need to be screened.

Bacterial pre-cultures:
Once per week a pre-culture is prepared taking one inoculation loop of bacteria from an agar plate (BHI-agar) to be cultivated in Nutrient-Broth medium. Each day one inoculation loop from this pre-culture is used to inoculate 5 ml of Nutrient-Broth which is then cultured at 22 °C.

Active sewage sludge or activated sludge:
This is taken from the aerated compartment of an Husmann apparatus and has to be prepared freshly on a weekly basis.
Test type:
not specified
Water media type:
not specified
Limit test:
Total exposure duration:
24 h
Remarks on exposure duration:
No data
Post exposure observation period:
No data
No data
Test temperature:
25 ± 2 °C
No data
Dissolved oxygen:
No data
No data
Nominal and measured concentrations:
Tested are 1, 5, 10, 20, 50, 100, 200 and 300 ppm of a test substance. In special cases 1, 3.2, 10, 32, 100, 320 and 1000 ppm are used (as indicated in the short report). A dilution scheme is attached to the original German version of the method description. 0.2 ml of the dilution is mixed with 15 ml of liquid nutrient agar (tempered to 45 °C) and plated on sterile petri dishes (agar incorporation test). Solvent and growth controls have to be used in parallel. In case of the suspension test 0.1 ml of dilutions are mixed with 4.5 ml of Nutrient broth in a test tube.
Details on test conditions:
Suspension Test:
Test tubes are inoculated with one drop of the bacteria sewage sludge suspension and incubated for 12-24 hours at 25 ± 2 °C in an incubator.
Reference substance (positive control):
not specified
21 d
Dose descriptor:
Effect conc.:
> 300 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Details on results:
No data
Results with reference substance (positive control):
No data
Reported statistics and error estimates:
No data
Validity criteria fulfilled:
not specified
BST >300 mg/l
Executive summary:

BST >300 mg/l

Description of key information

Activated sludge was exposed to FAT 20077 to assess the toxicity to microorganisms. About 100 ml of the underrun of a STP is taken and filtered through a sterile filter. Subsequently this filtrate is used to prepare the following dilutions. The toxicity value to activated sludge for FAT 20077 was found to be greater than 300 mg/

Key value for chemical safety assessment

EC50 for microorganisms:
300 mg/L

Additional information