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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
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: direct application
- Preliminary investigation: test of water-solubility: 2 g/L; not completely soluble in Aqua dem. (stirring time ca. 3 h), pH-value ca. 7.2.
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Laboratory culture: municipal activated sludge obtained from a laboratory wastewater treatment plant fed with municipal sewage and synthetic wastewater.
- Final dry solids concentration: 1 g/L
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
30 min
Test temperature:
20 ± 2 °C
pH:
7.5
Nominal and measured concentrations:
Nominal concentrations: control and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer-vessel (nominal volume 250 mL)
- Fill volume: 250 mL
- Aeration: the inoculum was aerated during the night (24 h).

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Synthetic medium: 8 mL/vessel 100-fold concentrated OECD medium
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
30 min
Dose descriptor:
other: EC20 (NOEC)
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
No significant inhibition of respiration was measured up to the highest tested concentration of 1000 mg/L (nominal).
Results with reference substance (positive control):
The 0.5h-EC50 of the control substance 3,5-dichlorophenol was ca. 6.2 mg/L and thus within the required range of 5-30 mg/L.
Validity criteria fulfilled:
yes
Conclusions:
The inhibition of the degradation activity of activated sludge is not anticipated when introduced to biological treatment plants in appropriate low concentrations.

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when introduced to biological treatment plants in appropriate low concentrations.

Key value for chemical safety assessment

Additional information

Changes in the respiration rate of activated sludge when exposed to the substance were investigated in a OECD 209 guideline study (BASF AG, 1998). The respiration of domestic activated sludge was monitored for 30 minutes. The sludge bacteria were not affected by the substance. An EC50 of ≥ 1000 mg/L was determined from the test.