potassium (oxido-NNO-azoxy)cyclohexane; cyclohexylhydroxydiazene 1-oxide, potassium salt; [K-HDO]

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22.03.1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1993

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Cyclohexylhydroxydiazene 1-oxide, potassium salt

EC Number:

613-953-8

Cas Number:

66603-10-9

Molecular formula:

C6H11KN2O2

IUPAC Name:

Cyclohexylhydroxydiazene 1-oxide, potassium salt

Test material form:

liquid

Details on test material:

Xyligen 30F is a 30% aqueous solution of K-HDO.

Specific details on test material used for the study:

Test substance K-HDO, techn. 30%ig
Chemical name N-Cyclohexyldiazeniumdioxy-potassium
Molecular formula C6H13N203K
Molecular weight 200.28 (pure substance)
Batch number 74 N 9702
Odour Weak odour
Colour Colourless
Aggregate state Liquid
Density 1.13
Solubility in water Fully miscible
Instability against Acids
Storage Room temperature, darkness
Homogeneity Homogenous
Purity of the test substance Technical purity, 30 % active substance content

Sampling and analysis

Analytical monitoring:

not required

Remarks:

The test substance is fully miscible with water

Details on sampling:

O2 consumption has been determined after 30 minutes.

Test solutions

Vehicle:

no

Details on test solutions:

test concentrations: 2.8, 7.8, 39, 84, 202, 403, 812 mg/L

Test organisms

Test organisms (species):

activated sludge

Details on inoculum:

Inoculum: Activated sludge from laboratory sewage treatment plants running with municipal and synthetic waste water
Concentration in the test: 1 g/L dry substance
Synthetic nutrition medium: 8 ml/ test assay, 100-times concentrated OECD medium
Volume of the test assay: 250 ml
Incubation temperature: 20 ± 2°C

Study design

Test type:

not specified

Water media type:

other:

Remarks:

not applicable for an activated sludge test

Limit test:

no

Total exposure duration:

30 min

Post exposure observation period:

Not required

Test conditions

Hardness:

not required

Test temperature:

not specified

pH:

not specified

Dissolved oxygen:

not specified

Salinity:

not required

Conductivity:

not required

Nominal and measured concentrations:

Results are given as nominal values.

Details on test conditions:

The test has been performed according to the annex of the EEC directive 88/302/EEC 18 Nov. 1987 (Activated sludge respiration inhibition test)
This method corresponds to:
– OECD guidelines for testing of chemicals Activated sludge, respiration inhibition test 209; Paris 1993
– International standards ISO 8192-(1994) Water quality – test for inhibition of oxygen consumption by activated sludge
In the short-term respiration test, the effect of a test substance on the respiration of aerobe microorganisms after a short exposure time (30 up to 80 minutes) will be tested. The effective concentrations at which the respiration compared to a control value without test substance is inhibited for 20, 50 and 80 % (EC20, EC50, EC80) are the determined test results.
The EC20 value is the limit concentration at which toxic effects in biological sewage treatment plants have to be expected. The test concentration used for biological degradation tests should not exceed the EC20 value.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

30 min

Dose descriptor:

other: EC20

Effect conc.:

ca. 4.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Effect concentrations 2

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

ca. 30 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Effect concentrations 3

Key result

Duration:

30 min

Dose descriptor:

other: EC80

Effect conc.:

> 812 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

See tables below

Results with reference substance (positive control):

See tables below

Reported statistics and error estimates:

None reported

Any other information on results incl. tables

Results with test substance:

	Reference values			Mean value (reference substance)	Test substance concentrations
Concentration of test substance (mg/L)	-	-	-	-	812	403	202	84	39	7.8	2.8
O2consumption after 30 min. (mg O2/L·h)	22	23	23	23	5	6	7	9	11	14	23
Inhibition of respiration (%) after 30 min.	-	-	-	-	78	74	70	61	52	39	0

Results with positive control substance:

	Reference substance (MV)	Control substance
Substance concentration (mg/L)		1	10	100
O2consumption (mg O2/L x h)	23	20	8	2
Respiration inhibition (%)	0	-13	-65	-91

Effective concentrations EC-values:

	EC20(mg/L)	EC50(mg/L)	EC80(mg/L)	Maximum test concentration
K-HDO, techn. 30%	4.8	30	-	812
3,5-Dichlorophenol	ca. 1	ca. 5	ca. 38	1000

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

No respiration inhibition up to 4.8 mg/L

Executive summary:

The effect of the test substance (30% K-HDO in water) on the respiration of aerobe microorganisms in activated sludge after a short exposure time of 30 has been tested. According to the results of the study the effective concentrations after 30 minutes are as follows:

EC₂₀: 4.8 mg/L corresponds to 1.44 mg K-HDO/L (nominal)

EC₅₀: 30 mg/L corresponds to 9 mg K-HDO/L (nominal)

EC₈₀: > 812 mg/L* corresponds to > 243.6 mg K-HDO/L (nominal)

*At the highest concentration tested (812 mg/L 30% K-HDO in water) an inhibition of 78% was observed.