[No public or meaningful name is available]

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experiment start date - 01 February 2010; Experiment completion date - 04 February 2010; Study completion date - 08 April 2010.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: FAT 40851/A TE
Batch Number: TZ 5891 / BOP 02-09
Purity: 69.9 % all coloured components
Appearance: Orange powder
Expiry Date: July 31, 2014
Storage Conditions: At room temperature at about 20 °C

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test item amounts of 5.29, 16.30, 50.27, 160.27 and 500.75 mg were weighed by means of an analytical balance and transferred to the designated test vessels with 284 mL tap water. The test item was dissolved in the tap water by intense stirring for 15 minutes at room temperature.

- Controls: The reference item 3,5-dichlorophenol at nominal concentrations tested were 5, 16 and 50 mg/L

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): no vehicle used

- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): Not applicable, no vehicle used

- Evidence of undissolved material (e.g. precipitate, surface film, etc): After stirring, the appearance of the test media was evaluated, and all test concentrations were clear, orange solutions. Then, 16 mL synthetic sewage feed and 200 mL activated sludge inoculum were added

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: Not applicable
- Method of cultivation: Not applicable
- Provenance: Aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland) treating predominantly domestic wastewater
- Preparation of inoculum for exposure: Sludge was washed twice with tap water, treated by centrifugation, and the supernatant liquid phase was decanted.
- Pretreatment: Holding period of 3 days prior to use, sludge wa fed daily with 50 mL synthetic wastewater per litre (16 g peptone, 11 g meat extract, 3 g urea, 0.7 g NaCl, 0.4 g CaCl2 x 2H2O, 0.2 g MgSO4 x 7H2O, 2.8 g K2HPO4 filled up with deionised water to a final volume of 1 litre), pH of inoculum was adjusted from 8.3 to 7.0 with diluted sulfuric acid solution; sludged was aerated during incubation time of 3 hours
- Initial biomass concentration: 3 g dry mass per litre

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

measured in one control: 20 °C at the start and at the end of the incubation period

pH:

Test item: 7.5-7.8 at start and 8.2-8.3 at end
Control: 7.7 at start and 8.2 at end
Reference item: 7.4-7.5 at start and 8.2-8.7 at end

Dissolved oxygen:

Test item: 8.0-8.5 mg/L at start and 8.2-8.6 mg/L at end
Control: 8.3-8.4 at start and 8.1-8.4 at end
Reference item: 8.4-8.7 at start and 8.3-8.7 at end

Nominal and measured concentrations:

Nominal concentrations: 10, 32, 100, 320 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 2000-mL glass beakers
- Type: open
- Aeration: 3 hours during incubation
- Biomass loading rate: Inoculum had a sludge concentration of 3.2 g/L dry weight (1.3 g dry material per litre test medium)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water
- Intervals of water quality measurement: No information on water quality and test intervals is given

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
The respiration rate of a well-mixed sample of each test medium was measured in a BOD-flask after three hours incubation time (no further aeration) by measuring the dissolved oxygen concentration with an oxygen electrode (TWT TriOxmatic 300 and oxygen meter WTW Oxi 539 over a period of at least ten minutes.

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

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 that might cause a difference between measured and nominal values: none
- Effect concentrations exceeding solubility of substance in test medium: none

Results with reference substance (positive control):

- Results with reference substance valid: Yes
- Relevant effect levels: The EC50 of the reference substance was 13 mg/L, which is in the recommended range of 5 to 30 mg/L
- Other: none

Validity criteria fulfilled:

yes

Conclusions:

The test item had no significant inhibitory effect (≤10 %) on the respiration rate of activated sludge after the incubation period of 3 hours up to and including the highest test item concentration of 1000 mg/L.

Executive summary:

The inhibitory effect of the test item FAT 40851/A on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3-hour respiration inhibition test according to the EU Commission Directive 88/302/EEC, Part C.11, Commission Regulation (EC) No. 440/2008, Part C.11 and the OECD Guideline for Testing of Chemicals, No. 209. The following nominal concentrations of FAT 40851/A were tested: 10, 32, 100, 320 and 1000 mg/L. In addition, two controls and three different concentrations of the reference item 3,5-dichlorophenol (5, 16 and 50 mg/L) were tested in parallel. The results of these treatments confirmed suitability of the activated sludge and the method used. Up to and including the highest test concentration of 1000 mg/L the test item had no significant inhibitory effect (≤10 %) on the respiration rate of activated sludge after the incubation period of three hours. Thus, the 3-hour NOEC (EC10) of FAT 40851/A  to activated sludge microorganisms was at least 1000 mg/L. The 3-hour EC20, EC50 and EC80 could not be calculated, but were clearly greater than 1000 mg/L.

Description of key information

The EC50 value for inhibition was >1000 mg/L and the NOEC was equal to or greater than 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

The aquatic toxicity of the test item FAT 40851/A to microbial activity in sewage sludge was tested in a valid GLP activated sludge respiratory inhibition test in accordance with EU Method C.11. Activated sludge from a treatment plant processing predominantly domestic sewage was exposed to the substance for 3 hours under aerated conditions to a series of test concentrations ranging from nominal 10 to 1000 mg/L. The substance had no inhibitory effect (inhibition of <10 %) on the sludge activity up to and with the test concentration of 1000 mg/L. The EC50 value for inhibition hence was >1000 mg/L and the NOEC was equal to or greater than 1000 mg/L.