2-[[4-(dimethylamino)phenyl]azo]-1,3-dimethyl-1H-imidazolium chloride

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:

24Jul2018-30Nov2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2-[[4-(dimethylamino)phenyl]azo]-1,3-dimethyl-1H-imidazolium chloride

EC Number:

278-601-4

EC Name:

2-[[4-(dimethylamino)phenyl]azo]-1,3-dimethyl-1H-imidazolium chloride

Cas Number:

77061-58-6

Molecular formula:

C13H18N5.Cl

IUPAC Name:

2-[[4-(dimethylamino)phenyl]azo]-1,3-dimethyl-1H-imidazolium chloride

Test material form:

solid: particulate/powder

Details on test material:

Batch 1054934

Specific details on test material used for the study:

Identification: Basic red 51
Batch (Lot) Number: 1054934
Expiry date: 29 November 2020 (expiry date)
Physical Description: Violet powder

Study design

Oxygen conditions:

aerobic

Remarks:

utilising synthetic air <1ppm CO2

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Freshly obtained sludge was kept under continuous aeration until further treatment. Before use, sludge was coarsely sieved (1 mm) and washed with mineral medium. After treatment concentration of suspended solids (SS) was determined to be 2.4 g/L in concentrated sludge as used for the test. Magnetically stirred sludge was used as inoculum at an amount of 3 mL per litre of mineral medium, leading to a SS concentration of 7 mg/L.

Duration of test (contact time):

ca. 28 d

Initial test substance concentration

Initial conc.:

21.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Test duration
28 days for inoculum blank and test item (last CO2 measurement on day 29).
14 days for procedure and toxicity control (last CO2 measurement on day 15).
During the test period, test media were aerated and stirred continuously.

Test vessels
2 litre brown coloured glass bottles.
Milli- RO water
Tap-water purified by reverse osmosis (Milli- RO) and subsequently passed over activated carbon.

Stock solutions of mineral components
A) 8.50 g KH2PO4
21.75 g K2HPO4
67.20 g Na2HPO4.12H2O
0.50 g NH4Cl
dissolved in Milli- RO water and made up to 1 litre, pH 7.4 ± 0.2

B) 22.50 g MgSO4.7H2O dissolved in Milli- RO water and made up to 1 litre.
C) 36.40 g CaCl2.2H2O dissolved in Milli- RO water and made up to 1 litre.
D) 0.25 g FeCl3.6H2O dissolved in Milli- RO water and made up to 1 litre.
Mineral medium
1 litre mineral medium contains: 10 mL of solution (A), 1 mL of solutions (B) to (D) and Milli- RO water.
Barium hydroxide
0.0125 M Ba(OH)2 (Boom, Meppel, The Netherlands), stored in a sealed vessel to prevent absorption of CO2 from air.
Synthetic air (CO2 < 1 ppm)
A mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. Synthetic air was passed through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
Illumination
Test media were excluded from light.
Pre-incubation medium The day before start of the test (day -1) mineral components, Milli- RO water (ca. 80% of final volume) and inoculum were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.
Type and number of bottles
Test suspension: containing test item and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Procedure control: containing reference item and inoculum (1 bottle).
Toxicity control: containing test item, reference item and inoculum (1 bottle).
Preparation
At the start of the test (day 0), test and reference item were added to bottles containing microbial organisms and mineral components.
Volumes of suspensions were made up to 2 litres with Milli- RO water, resulting in the mineral medium described before.
Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle.

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 4 - <= 5

Sampling time:

28 d

Remarks on result:

other: Basic red 51 was not readily biodegradable under the conditions of the modified Sturm test performed

Details on results:

1. Reference item was biodegraded by at least 60% (actual result: 73%) within 14 days.
2. Difference between duplicate values for %-degradation of test item was always less than 20% (actual result: ≤ 1%).
3. Total CO2 release in the blank at the end of the test did not exceed 40 mg/L (48.7 mg CO2 per 2 litres of medium, corresponding to 24.4 mg CO2/L).
4. Inorganic Carbon content (IC) of test item (suspension) in mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since test medium was prepared in tap-water purified by reverse osmosis (Milli- RO water (Millipore Corp., Bedford, Mass., USA, carbon levels < 500 ppb)), IC was less than 5% of TC (mainly coming from the test item, 12 mg TOC/L).

BOD5 / COD results

Results with reference substance:

Reference item was biodegraded by at least 60% (actual result: 73%) within 14 days.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

In conclusion, Basic red 51 was not readily biodegradable under the conditions of the modified Sturm test presently performed. However, it should be noted that in the toxicity control Basic red 51 was found to possibly have an inhibiting effect on microbial activity.

Executive summary:

Relative biodegradation values calculated from measurements performed during the test period revealed no biologically relevant biodegradation of Basic red 51 (5% and 4%, based on ThCO2).

In the toxicity control, less than 25% biodegradation occurred within 14 days (14%, based on ThCO2). Therefore, the test item was assumed to possibly have an inhibiting effect on microbial activity.

Functioning of the test system was checked by testing the reference item sodium acetate, which showed a normal biodegradation curve.

In conclusion,Basic red 51 was not readily biodegradable under the conditions of the modified Sturm test presently performed.