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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Dec 12, 2006 - Feb 27, 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Version / remarks:
July, 2010
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Specific details on test material used for the study:
Purity: 99.9 %
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
The test substance was insufficiently soluble to permit addition via aqueous solution. Individually weighed quantities of test substance were added directly to the appropriate test vessels.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Activated sludge, micro organisms from a domestic waste water treatment plant was supplied by the sewage plant Darmstadt, Germany.

Preparation and Maintenance
Tue activated sludge was washed by centrifugation and the supernatant liquid phase was decanted. Tue solid material
was re-suspended in tap water and again centrifuged. The latter procedure was repeated twice. The washed sludge was re-suspended in tap water and sewage feed ( 50 mL per L) was added. The sludge was kept at room temperature under continuous aeration until use for one day.
Immediately before use, the dry weight of the activated sludge was detennined, and diluted to 3.5 g/L with tap water. Tue pH of the activated sludge was 7.9 and therefore no adjustment
was necessary.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
20 ± 2°C
pH:
7.01 - 7.25
Dissolved oxygen:
saturated
Nominal and measured concentrations:
10, 32, 100, 320 and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: ca 250 mL glass conical flask
- Type (delete if not applicable): open
- Aeration:compressed air supply
- No. of vessels per control (replicates): 1
- Sludge concentration (weight of dry solids per volume): 3 g/L
- Nutrients provided for bacteria: no
- Biomass loading rate:

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated tap water
- Particulate matter:
OTHER TEST CONDITIONS
- Adjustment of pH: yes

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Justification for using fewer concentrations than requested by guideline: n.a.
- Range finding study no
- Test concentrations: 10, 32, 100, 320, 1000 mg/L
Reference substance (positive control):
yes
Key result
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
3,5-DCP:
Total Respiration: 8.2 mg/L
Validity criteria fulfilled:
yes
Conclusions:
Based on the measured inhibition of respiration rates, neither EC20 nor EC50 could be calculated. Since the inhibition of respiration rates was clearly below 20% up
to and including the concentration of 1000 mg/L, the EC20 and EC50 can be assumed to be higher than 1000 mg/L. A NOEC can be established at 1000 mg/L since the respiration inhibition was clearly lower than 20% at this concentration.
Executive summary:

The informtion for this endpoint study record was obtained from an experimental study. The OECD GLP criteria were met and the methods applied are fully compliant with OECD TG 209.

Based on the measured inhibition of respiration rates, neither EC20 nor EC50 could be calculated. Since the inhibition of respiration rates was clearly below 20% up

to and including the concentration of 1000 mg/L, the EC20 and EC50 can be assumed to be higher than 1000 mg/L. A NOEC can be established at 1000 mg/L since the respiration inhibition was clearly lower than 20% at this concentration.

Description of key information

OECD 209 study (Reliability 1): NOEC = 1000 mg/L

Key value for chemical safety assessment

EC50 or LC50 for microorganisms:
1 000 mg/L
EC10, LC10 or NOEC for microorganisms:
1 000 mg/L

Additional information