2-hydroxyethanesulphonic acid, compound with 4,4'-[hexane-1,6-diylbis(oxy)]bis[benzenecarboxamidine] (2:1)

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:

October 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Specific details on test material used for the study:

Batch/Lot Number: 42964
Expiry Date: 31 January 2019
Purity: 99%
Storage Conditions: Controlled room temperature (15-25°C, below 70 RH%), protected from humidity

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic (adaptation not specified)

Details on inoculum:

Secondary effluent, microorganisms from a domestic waste water treatment plant.
The sludge was allowed to settle and then aerated until use.

Duration of test (contact time):

28 d

Initial conc.:

3.1 mg/L

Based on:

ThOD

Remarks:

about 5.983 mg O2/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The test was carried out in an incubator and controlled environment room (during the formulation and oxygen measuring) at a temperature of 22 ± 2°C according to guideline. The test flasks were placed into an incubator and kept at 21.4 - 23.2°C, in the
dark. The temperature was measured on weekdays during the experiment. The oxygen concentration of test water was 9.0 mg/L at the start of the test. The pH value of the test water was checked prior start of the experiment. The pH of the
test water was 7.22.

Preparation of Test Flasks:
Sufficient number of BOD flasks was cleaned with 5 - 10 mL of a wash liquid (2.5 g iodine and 12.5 g potassium iodide per litre of 1 % w/v sulphuric acid) by shaking well to coat the bottle walls. After allowing to stand for 15 minutes, the wash liquid was
poured off, and the bottles were thoroughly rinsed with tap water and deionised water. Then, the previously described test solutions were filled into the bottles bubble-free until the bottles were completely filled. Then they were tightly closed with glass
stoppers.

The number of test bottles was the follow:
 10 bottles containing the test item and inoculum
 10 bottles containing the reference item and inoculum (procedure control)
 10 bottles containing only inoculum (inoculum control)
 10 bottles containing the test item, reference item and inoculum (toxicity control)

Measurement of Total Oxidised N, Nitrite and Nitrate:
During the performed 14-days preliminary test the concentration of dissolved oxygen resulted a mean of 7.50 mg O2/L after 14 days of incubation in the test item flasks (1a and 1b), which resulted only a mean of 5.0 % biodegradation within 14 days of the test item, therefore measurement of the total oxidised nitrogen (nitrate and nitrite) concentrations was not performed during the definitive study.

Measurement of Temperature:
Temperature was measured continuously and registered on weekdays.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

a 14-days preliminary test was performed

Test performance:

The study met the validity criteria.

Key result

Parameter:

% degradation (O2 consumption)

Value:

1.7

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

1.7

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

3.4

Sampling time:

21 d

Details on results:

Dissolved Oxygen Concentrations at 28 Days:
7.85mg/L

Oxygen Depletion at 28 Days:
Flask 1a: 0.15mg/L
Flask 1b: 0.05mg/L

BOD at 28 Days:
Flask 1a: 0.05mg/L
Flask 1b: 0.02mg/L

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test item was not considered to have significant inhibitory effects on the secondary effluent microorganisms.
Based on the results of this study, the test item is considered not readily biodegradable.

Executive summary:

The test item Hexamidine diisethionate was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item Sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

The test system was a microbial inoculum of good quality, collected from a sewage plant for domestic sewage. The sludge was allowed to settle and then aerated until use.

Under the test conditions the percentage biodegradation of Hexamidine diisethionate reached a mean of 1.7 % after 28 days based on the ThOD of the test item.

According to the test guidelines the pass level for ready biodegradability is removal of 60 % ThOD. Therefore the test item is considered not readily biodegradable.

The reference item Sodium benzoate was sufficiently degraded to a mean of 78.3% after 14 days, and to a mean of 83.3 % after 28 days of incubation, based on ThOD, thus

confirming the suitability of the used inoculum.

In the toxicity control containing both, the test item and the reference item Sodium benzoate, a mean of 39.9 % biodegradation was noted within 14 days and 44.0% biodegradation after 28 days of incubation.

According to the test guidelines the test item can be assumed to be not inhibitory at the applied concentration level of 3.1 mg/L on the secondary effluent microorganisms because degradation was >25 % within 14 days.

Description of key information

The test item was not considered to have significant inhibitory effects on the secondary effluent microorganisms.

Based on the results of this study, the test item is considered not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

other: RECONSTITUTED WATER