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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:
From 14 June 2016 to 22 June 2016
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:
yes
Remarks:
The temperature in the experiment was in a range of 22.5 – 23.4.°C instead of 20.0 +/- 2.0 °C. This deviation was stated as uncritical.
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Remarks:
Monitoring of the concentration in chlorendic acid
Details on sampling:
no data
Vehicle:
no
Details on test solutions:
no data
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Name and location of sewage treatment plant where inoculum was collected: ESN (Stadtentsorgung Neustadt) sewage treatment plant in D-67435 NW-Lachen-Speyerdorf
- Preparation of inoculum for exposure: On the day before the experiment, the inoculum was taken from its source, washed, aer-ated and the dry matter was determined. Volume was adapted to the desired content of dry matter. The nutrient solution was thawed and the sludge was fed with 50 mL/L sludge. The stock solution of the test item was prepared and shaked for 24 hours.
- Pretreatment: Upon arrival in the test facility, the sludge was filtrated, washed with tap water 3 times and re-suspended in tap water. The activated sludge was aerated until usage in the test and fed daily with 50 mL synthetic sewage feed /L.
- Initial biomass concentration: 2.38 g of dry matter of sludge/l
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
1.03 mmol/L
Test temperature:
The temperature was in the range of 22.5 – 23.4°C
pH:
The pH was in the range of 7.0 - 7.6 in the test media
Dissolved oxygen:
no data
Salinity:
no data
Conductivity:
242 µS/cm at 25°C
Nominal and measured concentrations:
see additional information on materials and methods
Details on test conditions:
TEST SYSTEM
- Test vessel: SCHOTT-flasks
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 2000 mL
- Aeration: none
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): 2 before and 2 after measuring positive control and test item
- Sludge concentration (weight of dry solids per volume): 1.19 g suspended solids/L
- Nutrients provided for bacteria: medium prepared according to OECD TG 209

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

OTHER TEST CONDITIONS
- Adjustment of pH: none

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

TEST CONCENTRATIONS
- Test concentrations: 468, 213, 97, 44, 20, and 0 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
97 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
130 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: 95% Confidence Interval: 78 – 170 mg/L
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
670 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: 95% Confidence Interval: 490 – 1300 mg/L
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values:No observations were made which might cause doubts concerning the validity of the study outcome.
- Blank controls oxygen uptake rate: 28.95 mg oxygen per gram sludge in 1 hour
- Coefficient of variation of oxygen uptake rate in control replicates: 6.6%
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 9.6 mg/L
- Other: 95% Confidence Interval: 4.1 – 15 mg/L
Reported statistics and error estimates:
95% confidence interval was calculated.
Validity criteria fulfilled:
yes
Conclusions:
The test material induced a significant respiratory inhibition in the two highest concentrations tested with a EC50 calculated to be 670 mg/l.
Executive summary:

The toxicity of Chlorendic Anhydride to the microorganisms from activated sludge was determined in accordance to the OECD guideline for the testing of chemicals 209. As Chlorendic Anhydride forms Chlorendic Acid in aqueous medium, the degradation product was actually tested.

A 3 hours toxicity test was performed on activated sludge of a predominantly domestic sewage. The test was performed at concentrations of 0, 20, 44, 97, 213, and 468 mg/l with analytical monitoring and the EC50 value was determined based on inhibition of the respiration. Positive and negative controls were valid.

The test material induced a significant respiratory inhibition in the two highest concentrations tested with a EC50 calculated to be 670 mg/l.

Description of key information

The toxicity of Chlorendic Anhydride to the microorganisms from activated sludge was determined in accordance to the OECD guideline for the testing of chemicals 209. As Chlorendic Anhydride forms Chlorendic Acid in aqueous medium, the degradation product was actually tested.

A 3 hours toxicity test was performed on activated sludge of a predominantly domestic sewage. The test was performed at concentrations of 0, 20, 44, 97, 213, and 468 mg/l with analytical monitoring and the EC50 value was determined based on inhibition of the respiration. Positive and negative controls were valid.

The test material induced a significant respiratory inhibition in the two highest concentrations tested with a EC50 calculated to be 670 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
670 mg/L
EC10 or NOEC for microorganisms:
130 mg/L

Additional information