Ethylcyclohexane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1996-12-25 - 1997-03-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Deviations:

not specified

GLP compliance:

yes

Specific details on test material used for the study:

Purity 99.5%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Sampling method
(1) Urban wastewater: Returned sludge from sewage plants
(2) River, lakes, marshes and sea: The surface soil in the area of where the surface water and atmosphere converge
Mixing the old and new sludge:
The filtrate of the sludge sampled from the locations specified above (500mLeach) and the filtrate of old, previously tested activated sludge (5L) were mixed to prepare 10L, pH was adjusted to 7.0±1.0, and the mixture was aerated in the incubation tank.
Aeration:
External air was processed through a prefilter and used for aeration.
Incubation:
After pausing aeration of the incubation tank for approximately 30 minutes, approximately 1/3 volume of the total amount of supernatant was discarded. An equal amount of dechlorinated water was added and the aeration was resumed, and then synthetic sewage water*3was added to give a concentration of 0.1%inthe replaced supernatant. This operation was repeated once daily for incubation,and the resulting matter was used as activated sludge. The incubation was performed at temperature of 25°C±2°C.
Synthetic sewage water:
Glucose, peptone, and potassium dihydrogen phosphate were dissolved in dechlorinated water to give 5(W/V)%,and the pH was adjusted with sodium hydroxide to 7.0±1.0.
Control and use:
During incubation, appearance of the supernatant and formation of activated sludge were observed, and activated sludge was measured and recorded in terms of sedimentation, pH and temperature, and dissolved oxygen concentration. The biota of the activated sludge was observed using light microscopy as needed to ensure that no abnormalities were identified before use for the test.
Inspection of the activity and date of starting the use of activated sludge :
Examination of activity in activated sludge
The activity was examined before starting to use the activated sludge by using the reference standard material. In addition, the association with the old activated sludge was monitored.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Test solution incubation apparatus Closed system oxygen consumption measurement apparatus (coulometer, Okura Electric)
(Data processor, Asahi Techneion)
Study container 300 mL incubation bottle (modified type for volatile substance)
Carbon dioxide absorbent Soda lime, No. 1
(Wako Pure Chemical Industries, for carbon dioxide absorption)
Stirring method rotational stirring using a magnetic stirrer
Environmental condition Test solution incubation temperature 25°C ± 1°C
Test solution incubation period For 28 days

Reference substance:

aniline

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Key result

Parameter:

% degradation (test mat. analysis)

Value:

0

Sampling time:

28 d

Results with reference substance:

The degradation of aniline on days7and 14calculated from the BOD were 72%and 99%, respectively, demonstrating that the operating conditions used in this study were effective.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test result showed 0 % degradation by BOD and it was confirmed by the direct analysis with gas chromatography that more than 94 % of ethylcyclohexane remained after the cultivation period. Therefore, ethylcyclohexane is not readily biodegradable.

Executive summary:

The test result showed 0 % degradation by BOD and it was confirmed by the direct analysis with gas chromatography that more than 94 % of ethylcyclohexane remained after the cultivation period. Therefore, ethylcyclohexane is not readily biodegradable.

Description of key information

Ethylcyclohexane was tested for ready biodegradation in a Modified MITI Test according to OECD Guideline 301 C.

The test result showed 0 % degradation by BOD and it was confirmed by the direct analysis with gas chromatography that more than 94 % of ethylcyclohexane remained after the cultivation period. Therefore, ethylcyclohexane is not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed