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Ecotoxicological information

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:
2003-10-13 to 2004-02-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
Commission Directive 87/302/EEC, No. L 133
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to the very low water solubility of T002251, no stock suspension could be prepared. Test item amounts of 4.98, 15.72, 50.39, 163.07 and 493.16 mg were directly weighed, then 284 ml of tap water was added. The test item was mixed into the tap water by ultrasonic treatment over 10 min. and intense stirring over 24 hours at room temperature in the dark to dissolve a maximum concentration of the test item in the test media. The stirring period was chosen based on results of a pre-test. After addition of 16 mL synthetic sewage and 200 mL sludge inoculum at the start of the test, the final total test medim volume resulted in 500 mL.
- Controls: yes

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source: predominantly domestic wastewater treatment plant, ARA Ergolz II, Füllinsdorf, Switzerland
- Washing procedure: washed twice with tap water by centrifugation, supernatant liquid phase decanted and the solid material resuspended in tap water. The homogenized aliquot of final sludge suspension was weighed, dried, and ratio wet to dry weight calculated.
- Holding: an aliquot of washed sludge was suspended in tap water at 3 g dw/L, holding 3 days prior to testing, fed daily with 50 mL synthetic wastewater per L, kept at room temperature and continuous aeration.
- Initial biomass concentration: sludge concentration of 3.3 g/L dw
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
not applicable
Test temperature:
19-20°C
pH:
5.8-7.8
Dissolved oxygen:
7.0-8.4
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 10, 32, 100, 320, 1000 mg/L.
Details on test conditions:
TEST SYSTEM
- Test vessel: 2000-mL glass flasks, 500-mL fill-volume
- Aeration: continuously aerated by intense stirring on magnetic stirrers.
- Number of replicates: 1
- Number of control replicates: 2
- Biomass loading rate: sludge concentration of 3.3 g/L (dw basis).

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water + synthetic wastewater, as prescribed by guidelines

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): respiration rate measured after 3 h of exposure (well-mixed sample poured into a BOD flask and not further aerated, dissolved oxygen concentration measured with oxygen electrode (WTW TriOxmatic 300 and an oxygen meter WTW Oxi 539, Weilheim, Germany) and continuously recorded for 10-15 min)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study
- Test concentrations: no information
- Results used to determine the conditions for the definitive study: no information
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
162 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: could not be calculated
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
39 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Effect concentrations exceeding solubility of substance in test medium: no
- The 3-h EC20 = 51 mg/L.
- The 3-h EC80 = 518 mg/L.

Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 3-h EC50 = 12 mg/L (95% CI could not be calculated). This is within the recommended range of 5-30 mg/L confirming suitability of the activated sludge used.
Reported statistics and error estimates:
The 3-h EC50, EC20 and their 95% confidence limits were calculated as far as possible by Probit analysis. The NOEC was determined as the calculated 3-hour EC15
Validity criteria fulfilled:
yes
Conclusions:
An activated sludge respiration inhibition test (according OECD guideline 209) with activated sludge from a predominantly domestic wastewater treatment plant resulted in a 3-h EC50 of 162 mg T002251/L and a NOEC of 39 mg T0022511/L. The results of the study can be considered reliable without restriction.

Description of key information

The study of Grützner (2004), investigating the toxicity of T002251 to microorganisms according to OECD guideline 209, was considered as the key study for endpoint coverage. The 3-h ELR50 was 162 mg/L. The 3-h NOELR was 39 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
162 mg/L
EC10 or NOEC for microorganisms:
39 mg/L

Additional information