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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2011-08-16 - 2011-08-18
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
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 1,1-[[3-(dimethylamino)propyl]imino]bis(2-propanol)
- Physical state: liquid
- Analytical purity: 85.7%
- Impurities (identity and concentrations): not reported
- Lot/batch No.: PFW100241
- Stability under test conditions: not reported
- Storage condition of test material: at ambient temperature
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
- Nominal stock solution of 5000 mg/L 1,1-[[3-(dimethylamino)propyl]imino]bis(2-propanol) was prepared in reverse osmosis water, the day before use.
- pH was measured as 10.9 and adjusted to 7.0 with HCl.
- Test solutions were prepared by adding known volumes of stock solution to a total volume of 500 mL RO water, synthetic sewage and activated sludge.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
ACTIVATED SLUDGE
- Laboratory culture: no
- Source: obtained from Totnes Sewage Works, Totnes, Devon, UK; predominantly domestic origin and 2 days prior to exposure
- Method of cultivation:
* left to settle and decanted
* settled sludge was fed with 50 mL of OECD synthetic sewage feed per liter of sludge per day
* sludge was aerated at room temperature
- Preparation of inoculum for exposure: 153 mL of activated sludge was mixed with 16 mL of synthetic sewage and corresponding test substance and water to obtain the nominal tested concentrations in a final volume of 500 mL
- Initial biomass concentration: total filterable solids concentration in the culture determined on the day of the test was 4886 mg/L at a pH of 7.0; suspended solids in test solutions was 1500 mg/L at the start of testing

SYNTHETIC SEWAGE
- synthetic sewage was prepared as described by the OECD guideline
- excess amount was added to the settled activated sludge
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
Not reported
Test temperature:
20 ± 2 °C
pH:
- control: at start 7.0-7.1 and at end 6.1-6.2
- 1,1-[[3-(dimethylamino)propyl]imino]bis(2-propanol): at start 6.9-7.1 and at end 5.9-6.3
Dissolved oxygen:
Not applicable
Salinity:
Not applicable.
Nominal and measured concentrations:
Nominal concentrations: blank, 10, 100 and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: culture flask
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: fill volume of 500 mL, no other details reported
- Aeration: yes
- No. of vessels per concentration (replicates): 3 for 1000 mg/L and 1 for 10 and 100 mg/L
- No. of vessels per control (replicates): 2
- No. of vessels per concentration of reference substance (replicates): 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reverse osmosis water
- Culture medium different from test medium: no
- Intervals of water quality measurement: pH and temperature (with mercury-in-glass thermometer) were measured at start and end, respiration rate was measured at end of exposure

OTHER TEST CONDITIONS
- Adjustment of pH: yes, prior to start of exposure (to 7.0)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): respiration rate, measured after 3 hours in glass samples tubes into which microcathode oxygen electrodes were inserted, and expressed as mg/L/h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Range finding study: no
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
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:
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
Details on results:
- EC20(3h) > 1000 mg/L
- EC80(3h) > 1000 mg/L
- Less then 10 % inhibition was observed in all test flasks.
Results with reference substance (positive control):
- EC50(3h) = 9.8 mg/L, which is within the normal range of 2 to 25 mg/L.
- The results with the reference substance indicate that the sludge in this test is responding normally and confirme the viability of the sludge organisms.
Reported statistics and error estimates:
none
Validity criteria fulfilled:
yes
Conclusions:
In this study, activated sludge from a predominantly domestic WWTP was exposed to 10, 100 and 1000 mg/L of test substance for 3 h, after which the oxygen consumption rate was measured. No significant differences in oxygen consumption rate were observed compared to the control. Therefore, the EC50 and NOEC were concluded to be > 1000 mg/L and >= 1000 mg/L, respectively.

Description of key information

A study performed under GLP conditions and according to OECD TG 209 showed no effects up to and including the highest test concentration. The EC50 and NOEC were > 1000 mg/L and >= 1000 mg/L, respectively (Harrigan and Daniel, 2011).

Key value for chemical safety assessment

Additional information

A reliable (K1) study is available to cover this endpoint.