Phosphinylidynetrimethanol

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:

2020-01-10 - 2020-02-07 (experimental phase)

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:

OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", 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:

Commission Regulation 440/2008/EC, Method C.4-D of May 30, 2008: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sewage treatment plant Rossdorf, Germany
- Pretreatment: The aerobic activated sludge used for this study was deposited for 30 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended 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. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated. This suspension was used for the experiment.
- Concentration of sludge: Stock suspension of 3.5 g/L on dry matter base (final sludge concentration in test flasks: 28.7 mg sludge/L)
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

103.1 mg/L

Based on:

test mat.

Initial conc.:

71.7 mg/L

Based on:

act. ingr.

Initial conc.:

73.7 mg/L

Based on:

other: ThOD (NH4) of the a.i.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
Reconstituted test 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 ultrapure water.

- Test temperature: 19°C
- pH: 7.6 (measured at the start of the test), 7.6 to 7.7 (measured at the end of the test)
- pH adjusted: yes
- Suspended solids concentration: 28.7 mg sludge/L (final sludge concentration)
- Continuous darkness: yes
- Other: surrounding type: climatised chamber

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL. The test flasks were closed gas-tight by a measuring head;
- Number of culture flasks/concentration: 2 (17.3 mg and 17.7 mg active ingredient of THPO/ flask);
- Measuring equipment: The pressure decrease in the reaction vessels was measured daily over complete experimental phase of 28 days using the BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany.
- Volume of test vessels: 500 mL
- Final volume of test solution: 244 mL

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 (inoculumn + test water)
- Abiotic sterile control: 1 (test item + CuSO4 (5 mL of a 1 g/L stock solution) + test water)
- Toxicity control: 1 (test item + reference item sodium benzoate + inoculumn + test water)
- Other: Procedure control: 1 (reference item sodium benzoate + inoculumn + test water)

Reference substance:

benzoic acid, sodium salt

Test performance:

No observations were made which might cause doubts concerning the validity of the study outcome.

Key result

Parameter:

% degradation (O2 consumption)

Value:

7

Sampling time:

28 d

Results with reference substance:

The percentage degradation of the reference item should reach the level for ready biodegradability (>60%) within 14 days as required by the test guideline.
The reference item sodium benzoate was sufficiently degraded to 68% after 14 days and to 74% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

- not readily biodegradable based on ThOD(NH4).
- mean biodegradation at test end after 28 days was 7% (mean, ThOD(NH4))

Executive summary:

The biodegradability of the test substance Phosphoryltrimethanol (THPO) was investigated under GLP according to EU method C.4 -D and OECD guideline 301F in a manometric respirometry test. The degradation rate of the test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

Aerobic activated sludge from a domestic wastewater treatment plant was used as inoculum. Analytical grade salts were added to deionised water to prepare the stock solutions.

A measured volume of inoculated mineral medium, containing the test item in a concentration of 71.7 mg a.i./L (corresponding to a ThOD_NH4of 73.7 mg a.i./L), was stirred in a closed flask at a constant temperature for up to 28 days. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.Also a toxicity control (test item and reference item mixed) was run in parallel, to ensure, that the chosen test concentration was not inhibitory to the aerobic activated sludge microorganisms.

The reference item sodium benzoate was sufficiently degraded to 68% after 14 days and to 74% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

In the toxicity control containing both, the test item and the reference item sodium benzoate, 55% (ThOD_NH4) biodegradation was noted within 14 days and 61% (ThOD_NH4) biodegradation after 28 days of incubation. 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.

 

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.

The test item never reached 10% biodegradation. The mean biodegradation at test end after 28 days was 7% (mean,ThOD_NH4). Therefore, THPO is considered to be not readily biodegradable based on ThOD_NH4. 

Description of key information

- 7 % biodegradation after 28 days [using the manometric respirometry test of OECD 301F, EU Method C.4 -D; GLP];

- Tris(hydroxymethyl)phosphine oxide (THPO) is considered to be not readily biodegradable based on ThOD_NH4

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The biodegradability of the test substance Phosphoryltrimethanol (THPO) was investigated under GLP according to EU method C.4 -D and OECD guideline 301F in a manometric respirometry test. The degradation rate of the test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

A reliability score of 1 was assigned, in accordance with the criteria for assigning data quality in line with the principles described by Klimisch (1997).

Aerobic activated sludge from a domestic wastewater treatment plant was used as inoculum. Analytical grade salts were added to deionised water to prepare the stock solutions.

A measured volume of inoculated mineral medium, containing the test item in a concentration of 71.7 mg a.i./L (corresponding to a ThOD_NH4of 73.7 mg a.i./L), was stirred in a closed flask at a constant temperature for up to 28 days. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Also a toxicity control (test item and reference item mixed) was run in parallel, to ensure, that the chosen test concentration was not inhibitory to the aerobic activated sludge microorganisms.

The reference item sodium benzoate was sufficiently degraded to 68% after 14 days and to 74% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

In the toxicity control containing both, the test item and the reference item sodium benzoate, 55% (ThOD_NH4) biodegradation was noted within 14 days and 61% (ThOD_NH4) biodegradation after 28 days of incubation. 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. 

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.

The test item never reached 10% biodegradation. The mean biodegradation at test end after 28 days was 7% (mean,ThOD_NH4).Therefore, THPO is considered to be not readily biodegradable based on ThOD_NH4.