Methyl dihydrogen phosphate

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:

27 February to 25 July 2018

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch 34448
Purity 67.9 - 71.2 % Methyl dihyrdogen phosphate
Expiry 30 March 2022

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge from a biologic sewage treatment plant was used. The chosen plant is treating mostly household sewage.

The sludge was taken from the activation basin of the sewage treatment plant in D-67480 Edenkoben.
Date of collection: 28. Feb. 2018
Batch no: 20180228.
The sludge was filtrated, washed with medium 2x, and re-suspended in test medium. It was then aerated. The dry matter was determined as 4520 mg suspended solids/L.

Duration of test (contact time):

28 d

Initial conc.:

264 mg/L

Based on:

test mat.

Initial conc.:

100.06 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Preparation
The medium was prepared using the stock solutions. The dry matter of the inoculum was determined. A sufficient number of test vessels was provided. The stock solution the positive control was freshly prepared. The test item was pipetted directly into the test vessels. Before the start of the test, the cartridge of the measuring heads was filled with soda lime and the program parameters (duration of the test, volume of the test flasks and volume of the test solution) were selected.

Experimental Parameters
Test item concentration: 264 mg test item/L
ThOD concentration test item: 100.06 mg ThOD /L
Positive control concentration: 60 mg sodium benzoate/L (corresponding to 100.08 mg/L ThOD)
Number of control flasks: 3 (medium and inoculum)
Number of positive control flasks: 3 (sodium benzoate, medium and inoculum)
Number of test vessels: 3 (test item, medium and inoculum)
Abiotic control: 1 (test item and 10 mL 1% HgCl2 solution/L)
Toxicity control: 1 (200.14 mg/L ThOD)
Volume of test vessels: 500 mL (590 mL total volume including measuring head)
Volume test solution: 250 mL (toxicity flask 125 mL)
Concentration of suspended solids 25.0 mg/L
Temperature: 20.7 – 21.1 °C 21.4 – 22.2 °C (toxicity control)
Duration: 28 days

Start of the Test
The test vessels were filled with medium, then test item and positive control were added to the appropriate vessels and the pH was adjusted to 7.2 – 7.6. After pH-adjustment, the inoculum was added, the vessels were connected to the OxiTop® measuring heads and they were started via the OxiTop® Controllers.
Performance of the Test
The oxygen which was consumed by the content of the vessels was measured automatically by the test apparatus. After 28 days, the test was ended. Because the test item and positive control do not contain nitrogen, presence of nitrate and nitrite was not checked.

Calculation of Degradation
Oxygen Demand The oxygen demand of test item and positive control vessels and for each measuring point were calculated.

Reference substance:

benzoic acid, sodium salt

Test performance:

All validity criteria were met. Oxygen consumption in the blank controls and in the positive controls was normal, indicating that the test system has worked properly. As a plateau of degradation was reached it is considerable, that the maximal degradation of the test item under the stated test conditions was reached. The ThOD of the test item was calculated based on a theoretical formula of the test item, calculated asC1H5.58O4.45P1. The formula was based on elemental analysis. The sum of analysed elements (9.50% C, 4.45% H, 26.7% P, 56.3%O) was 97 %.

No observations were made which might cause doubts concerning the validity of the study outcome. The result of the test can be considered valid.

Key result

Parameter:

% degradation (O2 consumption)

Value:

71

Sampling time:

28 d

Details on results:

The degree of biodegradation reached 71 % after 28 days. Because the test item is a mixture the 10-day-window does not have to be taken into account. As degradation surpassed 60% in the course of the test, regardless of the 10-daya window Methyl dihydrogen phosphate is considered as readily biodegradable.

Results with reference substance:

85% degradation over 28 days based on O2 consumption.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Readily Biodegradable.

Executive summary:

The degree of biodegradation reached 71 % after 28 days. Because the test item is a mixture the 10-day-window does not have to be taken into account. As degradation surpassed 60% in the course of the test, regardless of the 10-daya window Methyl dihydrogen phosphate is considered as readily biodegradable.  

Description of key information

Readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater