Dimethylamine-borane (1:1)

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:

2017-03-20 to 2017-05-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 17, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

EEC Publication No. L 142/496, May 2008

Deviations:

no

GLP compliance:

yes

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.
- Pre-treatment: The aerobic activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined.
- Concentration of sludge: 3.5 g dry material per litre were mixed with test water

Duration of test (contact time):

28 d

Initial conc.:

103.7 mg/L

Based on:

test mat.

Remarks:

Test Item Loading Rate

Initial conc.:

281.6 mg/L

Based on:

ThOD

Remarks:

THOD NH4

Initial conc.:

394.3 mg/L

Based on:

ThOD

Remarks:

THODNO3

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Reconstituted water: Analytical grade salts were added to pure water to prepare the following stock solutions:
a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4 x 2 H2O, 0.5 g NH4Cl filled up with pure water to 1000 mL volume; The pH-value was 7.4.
b) 11.25 g MgSO4 x 7 H2O filled up with pure water to 500 mL volume
c) 18.2 g CaCl2 x 2 H2O filled up with pure water to 500 mL volume
d) 0.125 g FeCl3 x 6 H2O filled up with pure water to 500 mL volume
In order to avoid precipitation of iron hydroxide in the stock solution d), one drop of concentrated HCl per litre was added before storage. 50 mL of stock solution a) and 5 mL of the stock solutions b) to d) were combined and filled up to a final volume of 5000 mL with pure water.

- Test temperature: 22°C ± 1°C
- pH: 7.6 (measured at the start of the test); 7.6 to 7.9 (measured at the end of the test)
- pH adjusted: no
- Aeration of dilution water: No
- Suspended solids concentration: 3.5 g dry material per litre were mixed with test water; final sludge concentration in test flasks: 28.7 mg sludge/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL. BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany
- Number of culture flasks/concentration: Two replicates for DMAB (103.7 mg/L), two replicates for inoculum control, one replicate for the procedure control, abiotic control, and the toxicity control.
- Preparation of Test flask: The amounts of test item and reference item were directly weighed into the test flasks. No emulsifiers or solvents were used, but the solutions were dispersed by stirring to achieve a homogeneous solution of the test item.
- Incubation: The closed test flasks were incubated in a climatized chamber under continuous stirring.
- Measuring equipment: The consumption of oxygen was determined by measuring the change of pressure in the flasks. Evolved carbon dioxide was absorbed in an aqueous solution (45%) of potassium hydroxide.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Abiotic sterile control: 1 replicate
- Toxicity control: 1 replicate
- Other: Procedure control: 1 replicate

Test Parameters
- Measurement of Oxygen: The change of pressure in the test flasks was measured by means of a manometric method (BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany) each day.
- Temperature: The temperature was recorded by means of the automated software AMR Wincontrol©.
- pH-Value: 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

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Remarks:

(ThODNH4)

Value:

> 2 - < 3

Sampling time:

28 d

Details on results:

The test item Dimethylamine-borane contains nitrogen; therefore, the evaluation of biodegradation has to be based on ThODNH4 and ThODNO3. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10 % degradation. Dimethylamine-borane never reached 10 % biodegradation. After correction for the mean biochemical oxygen demand of the inoculum controls, the mean biodegradation of the test item at test end after 28 days was 3 % (ThODNH4) and 2 % (ThODNO3). See also Figure 1 and 2 further below.

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to 79 % after 14 days and to 90 % after 28 days of incubation. The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Biodegradation in the Toxicity Control

Percentage Biodegradation: In the toxicity control containing both, the test item and the reference item sodium benzoate, 32 % (ThOD_NH4) biodegradation was noted within 14 days and 36 % (ThOD_NH4) biodegradation after 28 days of incubation (25 % and 28 % based on ThOD_NO3). According to the test guidelines the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25 % within 14 days.

 

Abiotic Control

Oxygen Demand: The oxygen demand in the abiotic control was 0 mg/L during the test duration. There was no need to correct the degradation of the test item and toxicity control.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The mean degradation rate of dimethylamine-borane was 3 % after 28 days. Therefore, dimethylamine-borane is considered to be not readily biodegradable based on ThODNH4 / ThODNO3.

Executive summary:

The biodegradation of dimethylamine-borane was studied in reconstituted water (pH 7.4 – 7.6) inoculated with activated sludge from a domestic sewage treatment plant (stock suspension of 3.5 g/L on dry matter base and a final sludge concentration in test flasks of 28.7 mg sludge/L). Dimethylamine-borane was applied with 103 mg a.i./L.  The experiment was conducted in accordance with the OECD test guideline 301 F ”Ready Biodegradability: Manometric Respirometry Test”, and in compliance with the OECD-GLP standards. The test system consisted of test flasks containing a volume of approximately 500 mL. The pressure decrease in the reaction vessels was measured over complete experimental phase of 28 days using the BSB/BODSensor- System, Aqualytic Dortmund, Germany. The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide. The amount of O₂ consumed by the activated sludge was calculated from the decrease of pressure in the reaction vessel.

 

The test item dimethylamine-borane contains nitrogen; therefore the evaluation of biodegradation has to be based on ThOD_NH4and ThOD_NO3. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60 %, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10 % degradation. Dimethylamine-borane never reached 10 % biodegradation. After correction for the mean biochemical oxygen demand of the inoculum controls, the mean biodegradation of the test item at test end after 28 days was 3% (ThOD_NH4) and 2 % (ThOD_NO3).

The mean degradation rate of dimethylamine-borane was 3 % after 28 days. Therefore, dimethylamine-borane is considered to be not readily biodegradable based on ThOD_NH4/ ThOD_NO3.

Description of key information

The mean degradation rate of dimethylamine-borane in a test according OECD method 301 F was 3 % after 28 days. Therefore, dimethylamine-borane is considered to be not readily biodegradable based on ThOD_NH4 / ThOD_NO3.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Hammesfahr (2017) conducted a study on biodegradation in accordance with the OECD test guideline 301 F ”Ready Biodegradability: Manometric Respirometry Test”, and in compliance with the OECD-GLP standards. The test item dimethylamine-borane contains nitrogen; therefore the evaluation of biodegradation has to be based on ThOD_NH4and ThOD_NO3. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60 %, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10 % degradation. Dimethylamine-borane never reached 10 % biodegradation. After correction for the mean biochemical oxygen demand of the inoculum controls, the mean biodegradation of the test item at test end after 28 days was 3 % (ThOD_NH4) and 2 % (ThOD_NO3).

The mean degradation rate of dimethylamine-borane was 3 % after 28 days. Therefore, dimethylamine-borane is considered to be not readily biodegradable based on ThOD_NH4/ ThOD_NO3.