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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1992-08-10 to 1992-12-14
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
Analytical monitoring:
no
Details on sampling:
Not applicable
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)- Method: direct inclusion of test material to test vessels- Evidence of undissolved material (e.g. precipitate, surface film, etc): none stated
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Obtained from the Cottonwood Subdivision Wastewater Treatment Plant located in Franklin, Tennessee.One gallon of sludge collected on day of use.Sludge immediately aerated with low presure oil-free air and fed synthetc sewage feed at a rate of 50 mL/L.Triplicate 10 mL samples of the mixed sludge were dried at 100°C in a Fisherbrand drying oven, until a constant weight was achieved. Based on these results the sludge was diluted to produce a dry weight per unit volume of 4 g/L.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Post exposure observation period:
none
Hardness:
Not applicable
Test temperature:
20°C
pH:
not stated
Dissolved oxygen:
Initial dissolved oxygen concentration not specified.
Salinity:
not applicable
Nominal and measured concentrations:
1000 mg/L (stated as ppm)
Details on test conditions:
TEST SYSTEM- Test vessel:glass serum bottle- Type (delete if not applicable): open - Material, size, headspace, fill volume: 1L, BOD bottle oxygen probe used to eliminate airspace- Aeration: yes (oil-free low pressure air delivered using a glass pipet)- No. of organisms per vessel: 4g/L dry weight sludge - 200 mL innoculm added per vessel- No. of vessels per concentration (replicates): 2- No. of vessels per control (replicates): 2 (one bfore and one after test material and reference runs started)- No. of vessels per reference (replicates): 3 (0.5 mL, 5 mL and 50 mL)TEST MEDIUM Synthetic sewage mediumOTHER TEST CONDITIONS- Adjustment of pH: NoEFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Every 10 minutes or until a linear trace covering sufficient range of oxygen concentrations was obtained.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol (97% pure)
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
Key result
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
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: None specified- Effect concentrations exceeding solubility of substance in test medium: Yes, test concentrations higher than solubility.Replicate A of the sludge exposed to the test material showed a consumption of 0.48 mg O2/L over a period of 0.5 min; a consumption rate equal to 57.6 mg O2/L per hour. Replicate B showed a a consumption of 2.4 mg O2/L over a period of 3.17 min; a consumption rate equal to 45.8 mg O2/L per hour. Expressed as an inhibition of control values the two replicates produced inhibitions of -7.4% and 14.6% respectively.
Results with reference substance (positive control):
- Results with reference substance valid? Yes- Relevant effect levels: 50 ppm: 84.3% inhibition, 5 and 0.5 ppm: 10.5% inhibition. EC50 = 18.0 mg/L
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.
Executive summary:

Introduction

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals No. 209 "Activated Sludge, Respiration Inhibition Test".

Methods

Activated sewage sludge was exposed to an aqueous dispersion of the test item at a concentration of 1000 mg/L for a period of 3 hours at a temperature of 20 ± 2 deg. C with the addition of a synthetic sewage as a respiratory substrate. The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

Results

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of greater than 1000 mg/L and a No Observed Effect Concentration (NOEC) of 1000 mg/L. The reference item gave a 3-Hour EC50 value of 18.0 mg/L.

Description of key information

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals No. 209 "Activated Sludge, Respiration Inhibition Test".

Activated sewage sludge was exposed to an aqueous dispersion of the test item at a concentration of 1000 mg/L for a period of 3 hours at a temperature of 20 ± 2 deg. C with the addition of a synthetic sewage as a respiratory substrate. The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of greater than 1000 mg/L and a No Observed Effect Concentration (NOEC) of 1000 mg/L. The reference item gave a 3-Hour EC50 value of 18.0 mg/L.