Sodium 2-stearoyllactate

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:

20 Nov 2019 - 20 Jan 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

adopted July 17, 1992

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Hessisches Ministerium für Umwelt, Klimaschutz, Landwirtschaft und Verbraucherschutz; Wiesbaden; Germany

Test material

Test material information

Constituent 1

Reference substance name:

Sodium 2-stearoyllactate

EC Number:

246-929-7

EC Name:

Sodium 2-stearoyllactate

Cas Number:

25383-99-7

Molecular formula:

This reference substance is a UVCB of the NCS type. It is a complex mixture of compounds and therefore molecular formula, molecular weight, SMILES, InChI and structural formula cannot be given.

IUPAC Name:

sodium 2-hydroxy-2-methyl-3-oxoicosanoate

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany.
- Storage conditions: aerobic
- Storage length: over night
- Preparation of inoculum for exposure: The activated sludge used for this study was deposited for 15 min before it was washed by centrifugation and the supernatant liquid phase decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was performed three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per L (± 10%) were mixed with test water and then aerated until use. This suspension was used for the experiment.
- Concentration of sludge: 3.5 g/L on dry matter base (final sludge concentration in test flasks: 27.5 mg sludge/L)

Duration of test (contact time):

60 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

101.6 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

228.3 mg/L

Based on:

other: ThODNH4

Initial test substance concentration 3

Initial conc.:

228.6 mg/L

Based on:

ThOD

Remarks:

ThODNO3

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Reconstituted Test Water, prepared from analytical grade salts.
- Test temperature: 22 ± 1 °C
- pH: 7.4 (at the start of the test), 7.4 - 7.6 (at the end of the test)
- Suspended solids concentration: 27.5 mg sludge/L
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: BSB/BOD-Sensor-System, Aqualytic, Dortmund, Germany
- Number of culture flasks/concentration: 2
- Measuring equipment: BSB/BOD-Sensor-System, Aqualytic, Dortmund, Germany
- Test performed in open system: The test flasks were closed gas-tight by a measuring head.
- Details of trap for CO2 and volatile organics if used: A potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide.

SAMPLING
- Sampling frequency: The change of pressure in the test flasks was measured by means of a manometric method each day. The temperature was recorded by means of the automated software AMR Wincontrol. pH-values were measured in procedure control, a separately prepared test flask with test item (to prevent loss of test item in the test flasks) and a separately prepared test flask without test item (control) at test start and in all flasks at the end of the test, except in the abiotic and toxicity control, using a pH-electrode WTW pH 340i.

CONTROL AND BLANK SYSTEM
- Inoculum blank (activated sludge in test water): 2 replicates
- Abiotic sterile control: 1 replicate: test item and CuSO4 in test water.
- Toxicity control: 1 replicate: test item, reference item and activated sludge in test water.
- Procedure control: 1 replicate: reference item and activated sludge in test water.

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Parameter:

% degradation (O2 consumption)

Value:

69

Sampling time:

28 d

Remarks on result:

other: based on ThODNH4

% Degradation 2

Parameter:

% degradation (O2 consumption)

Value:

91

Sampling time:

60 d

Remarks on result:

other: based on ThODNH4

Details on results:

Biodegradation of test item:
The mean biodegradation after 28 days was 69% (ThODNH4). At the test end after 60 days the mean biodegradation was 91% (ThODNH4). Due to the fact that the substance is identified as an UVCB with structurally similar constituents, the 10-day window condition is not applicable and the pass level applied at 28 days is used according to section 4.1.2.9.5 of CLP Commission Regulation (EU) No 286/2011 of 10 March 2011.

Biodegradation in the Toxicity Control:
In the toxicity control containing both, the test item and the reference item sodium benzoate, 67% (ThODNH4) biodegradation was noted after 14 days and 28 days of incubation and 68% (ThODNH4) biodegradation was noted after 60 days.

BOD5 / COD results

Results with reference substance:

Reference item: The reference item sodium benzoate was sufficiently degraded to 60% after 5 days, to 86% after 28 days and to 97% after 60 days of incubation.

Any other information on results incl. tables

Table 1. Validity criteria of OECD

Criterion from the guideline	Study results	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	The difference of duplicate values at day 28 differed by 2% and at day 60 by 0% (based on ThODNH4).	Yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	The reference item sodium benzoate was degraded to more than 60% after 5 days of incubation.	Yes
The oxygen uptake of the inoculum blank is normally 20-30 mg O2/L and should not be greater than 60 mg/L in 28 days.	The oxygen demand of the inoculum control was 20 mg O2/L after 28 d and 27.5 mgO2/L after 60 d.	Yes

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Interpretation of results:

readily biodegradable