Bis(p-methoxyphenyl)iodonium bromide

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:

21 January 2019 - 30 April 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in isotonic saline solution with shaking and again centrifuged. This procedure was repeated twice.
Preparation of Activated Sludge Inoculum:
An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to dry weight determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 5 g dry material per litre was mixed with mineral medium (see Section 5.4) and then aerated under test conditions until use. The pH of the activated sludge inoculum after preparation was: 7.29, just before use: 7.38. A pH adjustment of activated sludge inoculum was not performed.
NaCl (for isotonic saline solution): Manufacturer: lach:ner; Batch Number: PP/2017/00996, Retest date: 24 November 2019

Duration of test (contact time):

ca. 28 d

Initial conc.:

ca. 5 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The test was carried out in a controlled environment room (during the formulation and oxygen measuring) at a temperature of 22 ± 2°C according to the guideline. The test bottles were incubated in a controlled environment room at 22 ± 2°C, in the dark. Temperature was measured continuously using min/max thermometer and recorded every day.
During pre-conditioning of activated sludge inoculum the temperature was 20.0-20.9oC; during the preparation, aeration and incubation of the mineral medium, preparation of test bottles (units), the temperature was 20.0-21.1oC.
During the incubation (28 days) of the test units the temperature range was the following: 19.9-20.1oC.
The oxygen concentration of test water (mineral medium) was in the range of 8-9 mg/L. It was measured at the start of the test and found to be 8.92 mg/L.
The pH was checked prior study start and found to be 7.38. A pH adjustment was considered as not necessary.
The test conditions were measured with suitable instruments and documented in the raw data.
Equipments
Large glass tank (volume:~30 L) and
Large glass bottles (volume: at least 5L),
Narrow necked, Winkler bottles with glass stoppers,
Funnels and coarse filter papers,
Oxygen and pH meter with appropriate O2 and pH electrode,
Aeration system, Moisture analyzer
Temperature controlled (in the range of 22 ±2oC with a temperature deviation of ±1oC) incubator with thermometer with exclusion of light,
Balance, Centrifuge, Ultrasonic bath.
Type and Size: Winkler bottles (300 mL, coded) with special neck and glass stoppers.
Identification: Each test flasks were uniquely identified with study number, test group, days of measurement and replicate number.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (DOC removal)

Value:

ca. 9.1

Sampling time:

28 d

Key result

Parameter:

% degradation (DOC removal)

Value:

ca. 9.4

Sampling time:

21 d

Key result

Parameter:

% degradation (DOC removal)

Value:

ca. 7.9

Sampling time:

14 d

Key result

Parameter:

% degradation (DOC removal)

Value:

ca. 6.5

Sampling time:

7 d

Key result

Parameter:

ThOD

Value:

ca. 1.22 other: mg O2/mg T.i

Results with reference substance:

The reference item Sodium benzoate was sufficiently degraded to a mean of 73.6 % after 14 days, and to a mean of 80.9 % after 28 days of incubation, based on ThODNH3, thus confirming the suitability of the used activated sludge inoculum.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test item was considered to be not ready biodegradable. According to the test guidelines the pass level for ready biodegradability is 60 % of ThODNH3.
According to the test guidelines the test item can be assumed as not inhibitory on the activated sludge microorganisms because the degradation in the toxicity control group was higher than 25 % within 14 days.
The percentage biodegradation of the reference item confirms the suitability of the used activated sludge inoculum.

Executive summary:

The purpose of this study was to determine the ready biodegradability of the test item DIMETHOXYDIPHENYL-IODONIUMBROMID. The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant in completely full and closed bottles in the dark at controlled temperature (22 ± 2 oC) for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item Sodium benzoate (at a concentration of 3.0 mg/L) was tested simultaneously under the same conditions as the test item, and functioned as a procedure control (reference control). Additionally, inoculum (containing the filtered inoculum, only) and toxicity (containing both the test item and reference item) controls were examined.
The chosen test item concentration of 5.0 mg/L investigated in the main test was based on the calculated theoretical oxygen demand (ThODNH3 assuming that no nitrification occurs) of 1.22 mg O2/mg test item and based on the information about the toxicity of the test item (based on preliminary toxicity test results).
Under the test conditions ready biodegradation of this test item was not noticed, the percentage biodegradation of DIMETHOXYDIPHENYL-IODONIUMBROMID reached a mean of 9.1 % after 28 days based on its ThODNH3. The highest biodegradability value of 9.4 % was noticed on the 21st day of the test.
The reference item Sodium benzoate was sufficiently degraded to a mean of 73.6 % after 14 days, and to a mean of 80.9 % after 28 days of incubation, based on ThODNH3, thus confirming the suitability of the used activated sludge inoculum. The biodegradability reached its plateau on about the 7th day and from this day the slight changes were considered as being within the biological variability range of the applied test system.
In the toxicity control containing both, the test item and the reference item, a mean of 28.8 % biodegradation was noted within 14 days and 33.3 % biodegradation after 28 days of incubation. Thus, the test item can be assumed to not inhibit the activated sludge microorganisms (higher than 25 % degradation occurred within 14 days). The biodegradability in the toxicity control reached its plateau on about the 7th day and from this day the slight changes were considered as being within the biological variability range of the applied test system.

Description of key information

The test item was considered to be not ready biodegradable. According to the test guidelines the pass level for ready biodegradability is 60 % of ThODNH3.
According to the test guidelines the test item can be assumed as not inhibitory on the activated sludge microorganisms because the degradation in the toxicity control group was higher than 25 % within 14 days. The percentage biodegradation of the reference item confirms the suitability of the used activated sludge inoculum.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater