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activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 October 2005 to 15 November 2005
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: test according to the guideline under GLP
according to
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
according to
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
not required
Details on test solutions:
500.1 mg test susbtance was added to 284 mL tap water and stirred for 20 minutes. Therafter 200 mL activated sludge and 16 mL synthetic waste water were added to reach a concentration of 1000 mg/L.
synthetic waste water according to OECD 209:
- peptone 16 g
- meat extract (or a comparable vegetable extract) 11 g
- urea 3 g
- sodium chloride (NaCl) 0.7 g
- calcium chloride dihydrate (CaC12, 2H2O) 0.4 g
- magnesium sulphate heptahydrate (MgSO4, 7H2O) 0.2 g
- anhydrous potassium monohdydrogen phosphate (K2HPO4) 2. 8g
- distilled or deionized water to 1 litre
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source of inoculum/activated sludge: waste water treatment plant ARA Ergolz II, Fuellinsdorf, Switzerland
- Storage length: 3 days (fed with synthetic waste water (50 mg/L))
- Sorage condition: aerated at room temperature
- Preparation of inoculum for exposure: washed twice with tap water, supernatant decanted, homogenized and dried
- Pretreatment: none
- Concentration of sludge at start of the test: 4 g dry weight/L (1.6 g dry material/L)
- Water filtered: no
- pH: adjusted form 8.6 to 7.1 with diluted sulfuric acid
Test type:
Water media type:
Limit test:
Total exposure duration:
3 h
Post exposure observation period:
measurement of respiratory rate over 10-15 minutes without aeration under continuous stirring
Test temperature:
20 °C
Dissolved oxygen:
8.4-8.6 mg/L
Nominal and measured concentrations:
nominal 1000 mg/L
Details on test conditions:
- Test vessel: 2000 mL glass
- Fill volume: 1000 mL
- number of vessels : 1 for test substance, 2 for inoculum control; 1 per concentration for positive controls
- Aeration: yes
- Stirring: continuously

EFFECT PARAMETERS MEASURED : respiration rate (dissolved oxygen concentration) over 10-15 minutes after 3 h exposure period with oxygen electrode

Reference substance (positive control):
3,5-dichlorophenol at 5, 16 and 50 mg/L
3 h
Dose descriptor:
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
respiration rate
Details on results:
inhibition was 0.4% compared to inoculum controls
Results with reference substance (positive control):
EC50 19 mg/L (probit analysis)
Reported statistics and error estimates:
Validity criteria fulfilled:
The NOEC is ≥ 1000 mg/L
Executive summary:

In a limit test according to OECD 209, 1000 mg/L of the substance did not lead to inhibition of the respiratory activity of activated sludge. The NOEC is ≥ 1000 mg/L.

Description of key information

In a limit test according to OECD 209, 1000 mg/L of the substance did not lead to inhibition of the respiratory activity of activated sludge. The NOEC is ≥ 1000 mg/L (RCC 2005)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information