2,2'-[1,2-ethanediylbis(oxy)]bis(ethanethiol)

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:

06/12/1992 to 08/06/1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Purity: 99,3 %

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The inoculum was obtained the day of the ensemencement from the activated sludge of the biological wastewater treatment plant from Versailles (France, 78) which handles predominantly domestic sewage. On arrival at the laboratory, the activated sludge was centrifuged at 20°C (4000g for 20 minutes) and the solid sewage inoculum pellet was re-suspended in test medium in order to manage a ratio of 1:150 between the solid and the test medium. Total micro-organisms were counted with Total Count Millipore: for the present study, the concentration of the inoculum was 1,18.106 bact/mL thus a concentration of 1,18.104 bact/mL in the inoculated media (1% of inoculum in the test medium).

Duration of test (contact time):

28 d

Initial conc.:

38.2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (DOC removal)

Value:

< 10

Sampling time:

28 d

Series	Flasks	Day 0	Day 3	Day 7	Day 10	Day 13	Day 17	Day 20	Day 24	Day 28
Test item	Ft1	0	-15	0	-18	-13	-17	-4	4	7
	Ft2	0	-8	3	-1	-3	-10	9	-9	1
	Ft3	ND	ND	ND	ND	ND	ND	ND	ND	ND
Procedure control	Fc	0	88	98	96	98	100	100	100	100
Sterile control	Fs	0	-6	5	2	-7	-1	8	8	3
Inhibition control	Fi	0	46	54	46	39	47	58	50	57
Adsorption control	Fa	0	-3	10-	7	-1	-7	16	6	9

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

According to the OECD 301 guideline, the pass level for ready biodegradability is 70% removal of DOC for respirometric methods. This pass value has to be reached in a 10-d window within the 28-d period of the test. The 10-d window begins when the degree of biodegradation has reached 10% removal of DOC and must end before day 28 of the test.
In this study a mean total < 10% degradation was achieved by day 28. As a consequence the test item was not readily biodegradable under the conditions of the test.

Executive summary:

The study was conducted in accordance with procedures outlined in OECD Guideline 301A (1992). The ready biodegradability of the test item was assessed over a 28-day period.

 

The test was conducted at a nominal loading rate of 38.2 mg/L.

A total of 7 bioreactors were used:one for the procedure control, one for the sterile control, one for the inhibition control, one for the adsorption control and three for th test item.

 

The results of the test were as follows:

 

% biodegradation (28 days)	Test item	Reference item	Toxicity Control
	<10%	100%	57%

 

The test item was not readily biodegradable under the conditions of the test as it failed to achieve a transition from 10% to 70% degradation in a 10-day window during the 28-day test.

The test item was not considered to be inhibitory to the microbial inoculum since the biodegradation observed in the toxicity control bioreactor was not less than 35% occurred within 14 days.

The definitive test met the validity criteria of the test guideline detailed as follows:

-  the difference of extremes of replicate values of the removal of the test item at the end of the test was less than 20%

- the percentage degradation of the reference compound has reached the pass level by day 14: > 70%

- the biodegradation observed in the toxicity control bioreactor was not less than 35%: 39% within 14 days,

Description of key information

The study was conducted in accordance with procedures outlined in OECD Guideline 301A (1992). The ready biodegradability of the test item was assessed over a 28-day period.

 

The test was conducted at a nominal loading rate of 38.2 mg/L.

A total of 7 bioreactors were used:one for the procedure control, one for the sterile control, one for the inhibition control, one for the adsorption control and three for th test item.

 

The results of the test were as follows:

 

% biodegradation (28 days)	Test item	Reference item	Toxicity Control
	<10%	100%	57%

 

The test item was not readily biodegradable under the conditions of the test as it failed to achieve a transition from 10% to 70% degradation in a 10-day window during the 28-day test.

The test item was not considered to be inhibitory to the microbial inoculum since the biodegradation observed in the toxicity control bioreactor was not less than 35% occurred within 14 days.

The definitive test met the validity criteria of the test guideline detailed as follows:

-  the difference of extremes of replicate values of the removal of the test item at the end of the test was less than 20%

- the percentage degradation of the reference compound has reached the pass level by day 14: > 70%

- the biodegradation observed in the toxicity control bioreactor was not less than 35%: 39% within 14 days,