Butanal, reaction products with aniline

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

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:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Direct weighings were prepared to give the different test item concentrations. The test item was added into Erlenmeyer flasks (incubation vessels) to about 130 mL deionised water and was stirred before testing (equilibration phase) overnight for 16 hours.
For the reference compound a stock solution at a concentration of 500 mg/L was prepared by dissolving 250 mg 3,5-Dichlorophenol in 5 mL of 1 N NaOH and diluting to 0.5 litre with deionised water. The pH was adjusted to pH 7 ± 0.5 with HCl.

Test organisms (species):

activated sludge

Details on inoculum:

- mixed population of aquatic microorganisms, origin of an aeration tank of a domestic sewage treatment plant (Municipal STP Cologne-Stammheim, Germany)
- pretreatment: aeration, daily feed with synthetic medium
- pH 7.4
- test concentration of the activated sludge: 800 mg/L suspended solids
- Preparation of inoculum for exposure:
- first, the sludge was settled and the supernatant was decanted
- after centrifuging (15 min at 4500 rpm and 20°C) the supernatant was decanted
- approx. 1 g of the wet sludge was dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry weight) suspended solids
- the calculated amount of sludge was first dissolved in synthetic medium and than filled up to a defined end volume with deionised water

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

no data

Test temperature:

20.1 (concerning the highest concentration of 1000 mg/l)

pH:

7.9 (concerning the highest concentration of 1000 mg/l)

Dissolved oxygen:

oxygen (mg/l): O2-start 4.8; O2-end 2.5 (concerning the highest concentration of 1000 mg/l)

Salinity:

no data

Nominal and measured concentrations:

10, 100, 1000 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
Before use the wet weight/dry weight relationship of the activated sludge was determined by drying 10 mL of sludge suspension. Subsequently, a sludge suspension of 2 g (dry weight)/L was prepared. The pH of this suspension was measured and adjusted to 6-8.
8 mL of the synthetic medium and 100 mL of activated sludge were added to the dissolved test item. The mixture was filled up with deionised water to 250 mL and aerated at 20 ± 2 °C.
The exposure medium with the reference substance was prepared by adding 8 mL of the synthetic medium, 100 mL of activated sludge and a defined amount of the stock solution to achieve the test concentrations, and was filled up with deionised water to 250 mL and aerated at 20 ± 2°C.
Control vessels (inoculated sample without test item) were prepared the same way.
Additional vessels to determine the physico-chemical oxygen consumption were prepared containing the test item, and the synthetic medium but no activated sludge.

- Test vessel: 300 mL glass Erlenmeyer flasks
- type of application: direct weighing
- temperature: 20 +/- 2 °C
- stirring period before start of incubation time: 16 h (equilibration phase)
- test concentration: 3 (10, 100, 1000 mg/L)
- test parameter: respiration rate
- incubationtime: 3 hours with permanent aeration

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol, concentration (5, 10, 20 mg/L) )

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:

EC10

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:

- analysis of the respiration rates: by probit analysis

Results with reference substance (positive control):

- EC50 of the reference compound 3,5-Dichlorophenol is in the range 5 – 30 mg/L

Validity criteria fulfilled:

yes

Remarks:

respiratory rates of the 2 controls differ less than 15 % from each other

Conclusions:

According to EU Method C.11, the test item showed 0.0 % respiration inhibition of activated sludge at the highest test item concentration of 1000 mg/L.

Executive summary:

In order to test the toxicity to microorganism of the substance, activated sludge from predominantly domestic sewage plant

was exposed to the test solution of three nominal concentrations of the substance (10, 100, and 1000 mg/L), blank control

solution and solution with positive reference substance for a period of 3 hours. Dissolved oxygen was recorded and

respiration rates were claculated. No physico-chemical oxygen consumption was observed at the highest concentration of

test substance. No respiration inhibition was observed at 10,100 and 1000 mg/L. This toxicity study is classified as acceptable and satisfies the guideline requirements for the toxicity study to microoragnisms.

Description of key information

According to EU Method C.11, the test item showed 0.0 % respiration inhibition of activated sludge at the highest test item concentration of 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

should read >1000 mg/L.