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

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1980

Report date:

1980

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD-Confirmatory test

Version / remarks:

OECD-Environment directorate proposed method for the determination of the biodegradability of surfactants used in synthetic detergents (Paris 1976)

Deviations:

not specified

GLP compliance:

no

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:

solid: particulate/powder

Details on test material:

Test item: (N-Cyclohexyl-diazeniumdioxy)-potassium
IUPAC name: Cyclohexylhydroxydiazene 1-oxide, potassium salt
Chemical name: Cyclohexylhydroxydiazene 1-oxide, potassium salt; synonyma: (N-Cyclohexyl-diazeniumdioxy)-potassium, K-HDO, K-NCH, Xyligen K powder, Xyligen K
Molecular formula: C6 H11 K N2 O2
Molecular mass: 182.27

Radiolabelling:

no

Study design

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

activated sludge

Duration of test (contact time):

41 d

Initial test substance concentration

Initial conc.:

100.7 mg/L

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

Test conditions according to OECD confirmatory test (Simulation Test – Aerobic Sewage Treatment: OECD 303 A: Activated Sludge Units)

Results and discussion

Half-life of parent compound / 50% disappearance time (DT50)

Key result

Compartment:

activated sludge

DT50:

ca. 26 d

Transformation products:

not measured

Evaporation of parent compound:

no

Details on results:

In a weakly loaded biologically active system a degradation of > 90% within 41 days was reached.

Any other information on results incl. tables

Test results:

Duration of the degradation test in days	Concentration of K-HDO in mg/L	Biodegradation in %
0	100.7	0
7	87.3	13
12	75.3	25
15	70.6	30
26	48.7	51
30	30.0	70
33	20.6	79
37	20.6	79
39	14.7	85
41	6.7	94

Applicant's summary and conclusion

Validity criteria

Validity criteria fulfilled:

not specified

Conclusions:

HDO is degraded biologically. In a weakly loaded biologically active system a degradation > 90 % within 41 days was reached.

Executive summary:

Preliminary examinations and tests have been shown that only a small decrease of the tested substance occurs in a laboratory plant under standardized conditions and with 10 mg/l HDO. Even after prolongation of the dwell time to 24 hours the rate of decrease is only approx. 20 %. The decrease of HDO is possibly due to the loss during the preparation of the procedure in connection with the analytical determination of the test substance. However this result does not necessarily means that K-HDO is persistent. The prolongation of the dwell time to 6 days before stopping the test showed an unexpected decrease of the test substance of 68 %. The enforcement of a long-term test should clarify if HDO is degraded by micro-organisms – even with low speed. For this purpose a procedure was developed that allows to keep a steady-state biological active system in function over a longer period. The dwell time of the test substance in the purification plant can be prolonged to weeks and months.

The test conditions used to test K-HDO follow the OECD-Environment directorate proposed method for the determination of the biodegradability of surfactants used in synthetic detergents, Paris 1976 (Simulation Test – Aerobic Sewage Treatment: OECD 303 A: Activated Sludge Units)

The results prove that HDO is degraded biologically. In a weakly loaded biologically active system a degradation > 90 % within 41 days was reached.