Diethyl bis(2-hydroxyethyl)aminomethylphosphonate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Duration of test (contact time):

28 d

Parameter:

other: CSB

Value:

20

Sampling time:

28 d

Validity criteria fulfilled:

not specified

Interpretation of results:

not readily biodegradable

Conclusions:

The biodegradation of the substance was determined with a manometic respiration test and showed a degradation of 20 % after 28 days. The substance is not readily biodegradable.

Executive summary:

The biodegradation of the substance was determined according to OECD guideline method 301 F. The manometric respiration test showed a degradation of 20 % after 28 days.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Origin: A sewage treatment works that treats predominantly domestic waste

Pre-treatment of the inoculum:
- A sample of activated sludge was collected on the day of the test and aerated in the laboratory for four hours
- A sample of the mixed liquor was then homogenised in a mechanical blender and allowed to settle for 50 minutes
- An aliquot of the supernatant was passed through a Whatman's GFC filter paper to remove coarse solids and the filtrate used as the inoculum for the test

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST PROCEDURE:
- Four test vessels (five-litre brown glass carboys) each containing mineral salts medium (MSMS), bacterial inoculum at a concentration of 1%, and test
material or sodium benzoate were prepared (Vessel No. 1: Inoculated MSMS; vessel no. 2: Inoculated MSMS +sodium benzoate (20 mg/L); vessel no. 3: Inoculated MSMS +test material (10 mg/L) and vessel no. 4: Inoculated MSMS +test material (20 mg/L); iIn each case the volume prepared was 3.5 litres
- The test material and the reference substance, sodium benzoate, were added to the vessels as aqueous solutions (1 g/L)
- Following the addition of the test and reference materials to the test vessels, samples (500 mL) were removed for the determination of pH and DOC
- Each vessel was then fitted with a stopper holding an air inlet tube reaching approximately 15 cm below the liquid surface and an air outlet just below the stopper
- The vessel contents were continuously flushed for 27 days with air that had been passed through twelve one-litre bottles containing 10 N sodium hydroxide and one containing 0.25 N barium hydroxide to remove C02
- The air outlet from each vessel was connected to three Drechsel bottles in series, each containing 0.025 N barium hydroxide (100 mL)
- The residual concentrations of barium hydroxide in the bottles nearest to the test vessels were determined at intervals by duplicate titration of 20 mL samples with hydrochloric acid (O.OSN), using phenolphthalein indicator
- Following the removal of the first Drechsel bottle in a series, the second was connected to the test vessel, and a bottle containing fresh barium hydroxide was connected to the outlet of the bottle at the end of the series
- On Day 27 of the test, titrations were undertaken and samples (approximately 100 mL) were removed from each test vessel for pH determination
- Concentrated hydrochloric acid (1 mL) was then added to each vessel to drive off inorganic carbon dioxide
- The contents of the vessels were aerated overnight and the final titrations carried out on Day 28
- At the end of the test, test and control samples for DOC analysis were passed through a 0.2 urn membrane filter, acidified with 0.5N phosphoric acid and sparged with nitrogen
- The rate of air flow through the apparatus was determined at intervals during the test
- The temperature of the test area was recorded using a maximum-minimium thermometer

Reference substance:

benzoic acid, sodium salt

Remarks:

(AR grade, product number S/2441)

Preliminary study:

The ten-day bacterial inhibition assay was conducted before the main test to determine whether the test item at concentrations of 2 and 10 mg/L inhibited the normal degradative activity of the bacterial inoculum on the reference material, sodium benzoate. The presence of test material at either test concentration had no significant effect, indicating that it was not inhibitory. Neither was it, itself, readily degradable in this preliminary test.

Key result

Parameter:

% degradation (DOC removal)

Value:

19

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Test concentration 20 mg/L

Key result

Parameter:

% degradation (DOC removal)

Value:

15

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Test concentration 10 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

11

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Test concentration 20 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

9

Sampling time:

28 d

Remarks on result:

other:

Remarks:

Test concentration 10 mg/L

Parameter:

COD

Value:

1.59 other: mgO2/mg

Remarks on result:

other: 101% of its theoretical oxygen demand {ThOD; 1.57 mg02/mg)

Remarks:

The mean of three determinations

Results with reference substance:

Sodium benzoate was degraded by 60% of its theoretical carbon dioxide production (TC02; 2.14 mgC02/mg), after six days and 89% after 28 days; DOC analysis indicated that the benzoate was 98% degraded.

Validity criteria fulfilled:

yes

Remarks:

(Ready biodegradability of ref. compound ≥ 60 % within 14 days; In the toxicity control degradation rates >25 % within 14 days; Total C02 evolution in inoculum blank < 70 mg/L medium (28th day); Replicates difference <20 %.)

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Diethyl bis(2-hydroxyethyl)aminomethylphosphonate showed between 15 and 19 % degradation depending on the different test concentration (10 mg/20 mg) after 28 days. Therefore, diethyl bis(2-hydroxyethyl)aminomethylphosphonate is considered to be “Not Readily Biodegradable“. The reference compound sodium benzoate showed approx. 77 % degradation after 14 days.

Executive summary:

The ready biodegradability has been assessed in the Modified Sturm Test (EEC Procedure C5, OECD Procedure 301B). The study was preceded by the determination of the chemical oxygen demand (COD), the total and dissolved organic carbon (TOC and DOC) content, and a ten-day bacterial inhibition assay conducted under the conditions of the Closed Bottle Test (EEC Procedure C6, OECD Procedure 301D). In the modified Sturm Test, appropriate volumes of a test solution of 1000 mg/L were added to amber glass culture vessels containing inoculated mineral salts medium to give nominal test concentrations of 10 and 20 mg/L. Control vessels contained inoculated mineral salts medium alone or inoculated mineral salts medium plus sodium benzoate (20 mg/L). Test and control vessels were aerated for 28 days with air that had been treated to remove carbon dioxide (C0₂). The C0₂ produced by each culture was trapped in a series of Drechsel bottles containing barium hydroxide which were connected to the outlet from each test vessel. The residual barium hydroxide was determined at intervals by titration with hydrochloric acid using phenolphthalein indicator. The concentrations of dissolved organic carbon (DOC) of control, reference and test mixtures were determined at the start and end of the test, and their pH at the start of the test and after 27 days.

The ten-day bacterial inhibition assay was conducted before the main test to determine whether the test item at concentrations of 2 and 10 mg/L inhibited the normal degradative activity of the bacterial inoculum on the reference material, sodium benzoate. The presence of test material at either test concentration had no significant effect, indicating that it was not inhibitory. Diethyl bis(2-hydroxyethyl)aminomethylphosphonate was not itself considered to be readily degradable under the conditions of this preliminary test. Oxygen was not consumed in vessels containing test item at 2 mg/L, at 10 mg/L, oxygen consumption was equivalent to 2% of its ThOD after ten days. Cumulative C0₂ production at test item levels of 10 and 20 mg/L (4.3 and 10.1 mg C0₂ respectively) was equivalent to 9% and 11% of the theoretical value, by Day 28. A degradation plateau may not have been attained in the test. DOC analysis of test mixtures indicated that at 10 and 20 mg/L, diethyl bis(2-hydroxyethyl)aminomethylphosphonate was degraded by 15% and 19% respectively. Therefore diethyl bis(2-ydroxyethyl)aminomethylphosphonate cannot be considered to be readily degradable.

Description of key information

Diethyl bis(2-hydroxyethyl)aminomethylphosphonate showed between 15 and 19 % degradation depending on the different test concentration (10 mg/L or 20 mg/L) after 28 days (OECD TG 301B/D; Jenkins, 1990). Therefore, diethyl bis(2-hydroxyethyl)aminomethylphosphonate is considered to be “Not Readily Biodegradable“. This result is supported by another biodegradation study (OECD TG 301 F; Mueller, 1991) with a degradation rate of 20 % observed within 28 days.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

A fully reliable, guideline, GLP study is available, and therefore considered as key. The ready biodegradability has been assessed in the Modified Sturm Test (OECD TG 301B). The study was preceded by the determination of the chemical oxygen demand (COD), the total and dissolved organic carbon (TOC and DOC) content, and a ten-day bacterial inhibition assay conducted under the conditions of the Closed Bottle Test (OECD TG 301D). The result of the key study is supported by a guideline (OECD TG 301F), non-GLP study.