Tetralithium 5,5'-[vinylenebis[(3-sulphonato-4,1-phenylene)azo]]bis[3-methylsalicylate]

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:

2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Pre-treatment of the test item: 25 mg of the active ingredient (= 29 mg of the test item) were weighed out on aluminium foil and both were added to the test flasks, filled with 200 mL of mineral medium. Afterwards the volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item/L.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, WWTP Odenthal)
- Date of collection : 2017-04-18
- Storage conditions: two days at room temperature under continuous stirring with aeration.
- Pretreatment: the sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant.
An aliquot of the wet sludge was dried in order to determine the wet weight / dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L.
The calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume.
- Concentration of sludge: 30 mg/L suspended solids

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 22 ± 1 °C
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes
- pH: 7.5 - 8.1 after 28 days

TEST SYSTEM
- Culturing apparatus: OxiTopControl System (WTW)
- Test volume : 250 mL
- Mixing : 1 magnetic stirrer per test vessel
- The consumption of oxygen (BOD) was determined by measuring the drop in pressure in the automated respirometer flasks. Evolved carbon dioxide was absorbed in sodium hydroxide. The amount of oxygen taken up by the test item (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of theoretical oxygen demand (ThOD).
- Degradation was followed by the determination of oxygen uptake and measurements were taken at frequent intervals to allow the identification of the beginning and end of biodegradation and the slope of the biodegradation curve.
- Because of the nature of biodegradation and of the mixed bacterial populations used as inoculum, determinations of test item and inoculum blank were carried out in triplicate and of reference compound in duplicate.
- The oxygen uptake was calculated from the readings taken at regular and frequent intervals, using the method given by the manufacturer of the equipment. At the end of incubation, the pH was measured in the flasks.
- The test item is a N-containing substance. Therefore, the concentration of nitrite and nitrate was determined at the start of the test. The oxygen consumed by nitrification was not determined after 28 days, because no degradation of the test item was observed.

CONTROL AND BLANK SYSTEM
- The endogenous activity of the inoculum was checked running parallel blanks with inoculum but without test item.
- A reference compound (sodium benzoate) was run in parallel to check the operation of the procedures.
Pre-treatment: 25 mg of the reference compound were weighed out on aluminium foil and both were added to the test flasks, filled with 200 mL of mineral medium. Afterwards the volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg reference compound /L.
- A toxicity control (test item and reference compound mixed, one replicate) was run in parallel, to ensure that the chosen concentration of the test item was not inhibitory to microorganisms.
Pre-treatment: 25 mg of the active ingredient (= 29 mg of the test item) and 25 mg of the reference compound were were added to the test flasks, filled with 200 mL of mineral medium. Afterwards the flask volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item and reference compound/L.
- Determination of nitrite nitrogen and nitrate nitrogen and the sum of both: by flow analysis (CFA and FIA) and spectrometric detection (Test Apparatus: Continuous Flow Analyser)

Parameter:

% degradation (O2 consumption)

Value:

2

Sampling time:

28 d

Details on results:

- no oxygen consumption by nitrification has been observed . The oxygen consumed by nitrification was not determined at the end of the study, because poor degradation of the test item was observed and the correction for oxygen uptake by nitrification would not have an influence on the results.
- used concentration of the test item is not toxic to bacteria

Results with reference substance:

Kinetic of reference substance ( % Degr.):
85 after 7 days
94 after 14 days
96 after 21 days
97 after 28 days

Validity criteria fulfilled:

yes

Remarks:

(-Ready biodegradability of reference compound 60 percent within 14 d -Toxicity control exhibited degradation rates > 25 % within 14 d -Replicates difference< 20% -Oxygen uptake of blank inoculum =< 60mg/L -No pH influence (6.0 and 8.5 at test end))

Interpretation of results:

not readily biodegradable

Conclusions:

Within 28 days, a degradation rate of 2 % was determined for Bayscript Gelbkomponente.

Executive summary:

To assess the ready biodegradability Bayscript Gelbkomponente was stirred in a 250 ml closed flask and inoculated at a constant temperature (22 ± 1 °C) for up to 28 days under aerobic conditions in the dark. The inoculum (activated sludge) was collected from an aeration tank of a wastewater plant treating predominantly domestic sewage. The consumption of oxygen (BOD) was determined by measuring the drop in pressure in the automated respirometer flasks. Evolved carbon dioxide was absorbed in sodium hydroxide. The amount of oxygen taken up by Bayscript Gelbkomponente (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of theoretical oxygen demand (ThOD). The endogenous activity of the inoculum was checked running parallel blanks with inoculum but without test item. A reference compound (sodium benzoate) was run in parallel to check the operation of the procedures. A toxicity control (test item and reference compound mixed, one replicate) was run in parallel, to ensure

that the chosen concentration of Bayscript Gelbkomponente was not inhibitory to microorganisms. Degradation was followed by the determination of oxygen uptake and measurements were taken at frequent intervals to allow the identification of the beginning and end of biodegradation and the slope of the biodegradation curve. Because of the nature of biodegradation and of the mixed bacterial populations used as inoculum, determinations of test item and inoculum blank were carried out in triplicate and of reference compound in duplicate. The oxygen uptake was calculated from the readings taken at regular and frequent intervals, using the method given by the manufacturer of the equipment. After 28 days a pH of 7.5 - 8.1 was measured in the flasks. The suspended solids concentration was 30 mg/L The concentration of Bayscript Gelbkomponente was 100 mg/L active ingredient. Bayscript Gelbkomponente is a N-containing substance. Therefore, the concentration of nitrite and nitrate was determined at the start and at the end of the test. The oxygen consumed by nitrification was not determined at the end of the study, because no degradation of the test item was observed and the correction for oxygen uptake by nitrification would not have an influence on the results

Within 28 days, a degradation rate of 2 % was determined for Bayscript Gelbkomponente. The reference compound sodium benzoate showed 94 % degradation after 14 days. Bayscript Gelbkomponente is not readily biodegradable.

Description of key information

Within 28 days, a degradation rate of 2 % was determined for Bayscript Gelbkomponente.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed