Reaction mass of didodecyl 3,3'-thiodipropionate and dioctadecyl 3,3'-thiodipropionate and octadecyl 3-[[3-(dodecyloxy)-3-oxopropyl]thio]propionate

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2006-02-23 to 2006-03-30 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

yes

Remarks:

1. instead of an effluent/extract/mixture, activated sludge was used as an inoculum, 2. stirring of the content of the bottles was introduced to improve the bioavailability of the test substance

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Dioctadecyl 3,3'-thiodipropionate

EC Number:

211-750-5

EC Name:

Dioctadecyl 3,3'-thiodipropionate

Cas Number:

693-36-7

Molecular formula:

C42H82O4S

IUPAC Name:

dioctadecyl 3,3'-sulfanediyldipropanoate

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Secondary activated sludge was obtained from the WWTP Nieuwgraaf in Duiven, The Netherlands (23-02-2006). The WWTP Nieuwgraaf is an activated sludge plant treating predominantly domestic waste water.
- Preparation of inoculum for exposure/pre-treatments/concentrations: A minor deviation of the test procedures described in the guidelines was introduced: instead of an effluent/extract/mixture, activated sludge was used as an inoculum. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 400 mg Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted to a concentration of 2 mg DW/L in the BOD bottles (van Ginkel and Stroo 1992).

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: The nutrient medium of the Closed Bottle test contained per liter of deionized water: 8.5 mg KH2P04, 21.75 mg K2HP04, 33.3 mg Na2HP04-2H20, 22.5 mg MgS04-7H20, 27.5 mg CaCI2, 0.25 mg FeCI3-6H20. Ammonium chloride was omitted from the medium to
prevent nitrification.
- Solubilising agent (type and concentration if used): Dioctadecyl-3,3'-thiodipropionate is a poorly soluble substance in water and therefore the test substance was first dissolved in dichloromethane (0.08 g/L). The test substance in dichloromethane (7.1 mL) was added to the respective bottles.
- Test temperature: 19-21 °C
- pH: 7 at test start, pH 6 at test end
- Aeration of dilution water: no
- Suspended solids concentration: 2 mg/L d.w.
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: Closed BOD bottles, completely filled. The bottles with the test substance and accompanying control were placed on magnetic stirrers to improve the bioavailability of the test substance. The content of the bottles with acetate and their accompanying controls were not mixed with magnetic stirrers.
- Number of culture flasks/concentration: 10



SAMPLING
- Sampling frequency: Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.
- Sampling method: The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, The Netherlands).


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes 10 bottles
- Abiotic sterile control: no
- Toxicity control: yes, 6 bottles
- Other: solvent control: 6 bottles


STATISTICAL METHODS:

Calculation of the theoretical oxygen demand (ThOD)
The ThODs of dioctadecyl-3,3'-thiodipropionate and of the sodium acetate were calculated from their molecular formulae and molecular weights.

Calculation of the biochemical oxygen demand (BOD)
Provided that the oxygen concentrations in all bottles at the start of the test were equal, the amounts of oxygen consumed in test and reference compound bottles were calculated as follows:
Oxygen consumption (mg/L) = Mc - MtOra

Mc = the mean oxygen level in the control bottles inoculated with activated sludge n days after the start of the test.
MtOra = the mean oxygen concentration in the bottles containing the test compound (t) or the reference compound, sodium acetate (a), and inoculated with activated sludge n-days after the start of the test.

The biological oxygen demand (BOD) mg/mg of the test compound and sodium acetate was calculated by dividing the oxygen consumption by the concentration of the test substance and sodium acetate in the closed bottle, respectively.

Calculation of the biodegradation percentages
The biodegradation was calculated as the ratio of the biochemical oxygen demand (BOD) to the theoretical oxygen demand (ThOD).

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Parameter:

% degradation (O2 consumption)

Value:

71

Sampling time:

28 d

% Degradation 2

Parameter:

% degradation (O2 consumption)

Value:

60

Sampling time:

21 d

% Degradation 3

Parameter:

% degradation (O2 consumption)

Value:

47

Sampling time:

14 d

% Degradation 4

Parameter:

% degradation (O2 consumption)

Value:

24

Sampling time:

7 d

% Degradation 5

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

0 d

BOD5 / COD results

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 81.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

1) endogenous respiration of 0.8 mg/L at day 28, 2) differences of the replicate values at day 28 were less than 20%, 3) biodegradation reference compound, sodium acetate, at day 14 was 81. 4) oxygen concentrations >0.5 mg/L in all bottles during test

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

-Dioctadecyl-3,3'-thiodipropionate did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum.
-Dioctadecyl-3,3'-thiodipropionate was biodegraded 71% at day 28 in the Closed Bottle test and therefore the criteria for ready biodegradability' as given in the guideline is fulfilled.