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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-05-05 to 2010-05-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)
GLP compliance:
yes
Specific details on test material used for the study:
Batch No.: 20091203
Purity: 99.42%
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
- Test item was dispersed directly into water.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Method of cultivation: Maintained on a continuous aeration in the laboratory at a temperature of approximately 21 °C and was used on the day of collection.
- pH: 7.1
- Suspended solids concentration: 3.9 g/L
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Hardness:
Approx. 140 mg/L as CaCO3
Test temperature:
21 °C ± °C
pH:
Control - 7.4 to 7.8
Test item - 7.6 to 7.7
35DCP - 7.5 to 8.1
Dissolved oxygen:
Control - 4.1 mg/L to 5.0 mg/L (initial), 1.9 mg/L to 2.0 mg/L (final)
Test item - 3.3 mg/L to 3.8 mg/L (initial), 1.5 mg/L to 1.8 mg/L (final)
35DCP - 5.7 mg/L to 7.9 mg/L (initial), 2.4 mg/L to 7.1 mg/L (final)
Salinity:
Before softening; min, typical, max concentrations:
- Na: 15.000 mg/L, 25.125 mg/L, 41.000 mg/L
- Cl: 15.200 mg/L, 22.563 mg/L, 26.8 mg/L
Nominal and measured concentrations:
Test item, nominal: 10 mg/L, 32 mg/L, 100 mg/L, 320 mg/L, 1000 mg/L.
Details on test conditions:
TEST SYSTEM
- Test vessel: 500 mL conical flask
- Type: Open
- No. of vessels per concentration (replicates): 1
- No. of vessels per negative control (replicates): 2
- No. of vessels per positive control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory tap water dechlorinated by passing through an activated carbon filter and partially softened.
- Total organic carbon: 0.740 mg/L (minimum), 1.018 mg/L (typical), 1.390 mg/L (maximum)
- Particulate matter: No data
- Metals: No data on total metals
- Pesticides: 0.000 µg/L (minimum), 0.001 µg/L (average), 0.005 µg/L (maximum)
- Chlorine: 0.040 mg/L (minimum), 0.248 mg/L (average), 0.480 mg/L (maximum)
- pH: 7.16 (minimum), 7.624 (average), 7.980 (maximum)
- Ca/Mg ratio: No data
- Conductivity: 288.000 µS/cm at 20 °C (minimum), 386.192 µS/cm at 20 °C (average), 493.000 µS/cm at 20 °C (maximum)
- Intervals of water quality measurement:

OTHER TEST CONDITIONS
- Light intensity: Normal laboratory lighting

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2/3.125

EVALUATION OF DATA
- In order to calculate the inhibitory effect of the test and reference items the respiration rate was expressed as a percentage of the two control respiration rates:
- The EC15, EC20, EC50 and EC80 values for the test item were determined by the inspection of the inhibition respiration rate data.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
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
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
NOEC
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.
- Relevant effect levels:
-- EC20: 2.9 mg/L
-- EC50: 8.8 mg/L (95 % confidence limits: 6.9-11 mg/L)
-- EC80: 27 mg/L
-- NOEC: 2.4 mg/L
Reported statistics and error estimates:
- The % inhibition values were plotted against concentration for the reference item only, a line fitted using the Xfit software package (IDBS) and the EC₁₅, EC₂₀, EC₅₀ and EC₈₀ values determined from the equation for the fitted line.
- 95 % confidence limits were calculated for the reference item EC₅₀ value using the method of Litchfield and Wilcoxon (1949).
Validity criteria fulfilled:
yes
Remarks:
Met both following validity criteria: 1. That the control respiration rates were within 15 % of each other. 2. The 3 hr EC50 for 35DCP was within 5-30 mg/L.
Conclusions:
The effect of the test item on the respiration of activated sewage sludge gave a 3 hour EC50 of greater than 1000 mg/L. The NOEC after 3 hours was 1000 mg/L.

Description of key information

3 hour EC50 >1000 mg/L (OECD 209)

Key value for chemical safety assessment

Additional information

The test substance was assessed for activated sludge respiration according to OECD Guideline 209. The effect of the test item on the respiration of activated sewage sludge gave a 3 hour EC50 of greater than 1000 mg/L. The NOEC after 3 hours was 1000 mg/L.