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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
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
Deviations:
no
GLP compliance:
yes
Test organisms (species):
activated sludge of a predominantly domestic sewage
Test type:
static
Water media type:
freshwater
Total exposure duration:
3 h
Test temperature:
20°C±2°C
pH:
6.2-8.2
Nominal and measured concentrations:
Range finding test
- Nominal: Control and 10, 100 and 1000 mg/L potassium dicyanoargentate
Definitive test
- Nominal: Control, 0.64, 2.0, 6.4, 20, 64 and 250 mg/L potassium dicyanoargentate
Details on test conditions:
TEST SYSTEM
- Fill volume: filled to 100 mL
- Aeration: aerated
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 4
- No. of vessels per reference substance (replicates): 5

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reverse osmosis

- Range finding study
- Test concentrations: Control and 10, 100 and 1000 mg/L potassium dicyanoargentate
- Results used to determine the conditions for the definitive study: An EC50 value for potassium dicyanoargentate was estimated from the data to be 142 mg/L.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
1.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95%CL 1.5-2.3 mg/L
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
1.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95%CL 1.0-1.2 mg/L
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
6.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95%CL 5.4-6.5 mg/L
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
0.64 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:
LOEC
Effect conc.:
2 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):
The reference substance, 3,5-DCP, caused substantial inhibition of the respiration rate of the activated sludge. From the results obtained the 3 hour EC50 value was estimated to be 7.6 mg/L. This is within the expected normal range of 2 to 25 mg/L indicating the sludge was responding normally and confirming the viability of the sludge organisms.
Reported statistics and error estimates:
The EC50, EC20, EC80 and NOEC for respiration inhibition for potassium dicyanoargentate, together with their 95% confidence intervals, were calculated by Linear interpolation using the US EPA program ICPIN (version 2, June 1993).
The data was assessed for normality using the Anderson-Darling normality test. Some treatments were non-normal, so all treatments were compared against a median respiration inhibition of zero % using 1-sample Wilcoxon test.
Validity criteria fulfilled:
yes
Conclusions:
The 3-hour EC50 based on respiration rate for activated sludge is 1.9 mg/L. The 3-hour NOEC based on respiration rate for activated sludge is 0.64 mg/L.
Executive summary:

A 3-hour respiration inhibition test based on total respiration was carried out on activated sludge from mainly domestic sewage according to OECD guideline 209. A reference substance test, range finding test and definitive test were carried out. Based on five replicates (4 for the control), 3-hour EC50, EC20, EC80, NOEC and LOEC values (nominal) are reported based on respiration rate.

The 3-hour EC50 based on respiration rate for activated sludge is 1.9 mg/L. The 3-hour NOEC based on respiration rate for activated sludge is 0.64 mg/L.

Description of key information

The 3-hour EC50 based on respiration rate for activated sludge is 1.9 mg/L. The 3-hour NOEC based on respiration rate for activated sludge is 0.64 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1.9 mg/L
EC10 or NOEC for microorganisms:
0.64 mg/L

Additional information

A 3-hour respiration inhibition test based on total respiration was carried out on activated sludge from mainly domestic sewage according to OECD guideline 209 (Brixham 2012b). A reference substance test, range finding test and definitive test were carried out. Based on five replicates (4 for the control), 3-hour EC50, EC20, EC80, NOEC and LOEC values (nominal) are reported based on respiration rate. The 3-hour EC50 based on respiration rate for activated sludge is 1.9 mg/L. The 3-hour NOEC based on respiration rate for activated sludge is 0.64 mg/L.

Supporting data are available from a published non-guideline, non-GLP study on Pseudomonas resinovorans (Bouari et al. 2013). Five concentrations were tested in solution, alongside an ammonium chloride control. Effects were observed at the lowest concentration tested. The 24 -hour LOEC is determined to be 1.56 mM. As this is a non-standard study and a guideline activated sludge respiration inhibition study is available for this substance, this is used as supporting data only.