Methyl hydrogen octadecylphosphonate

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

7 September 2005 to 6 October 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methyl hydrogen octadecylphosphonate

EC Number:

246-905-6

EC Name:

Methyl hydrogen octadecylphosphonate

Cas Number:

25371-55-5

Molecular formula:

C19H41O3P

IUPAC Name:

methoxy(octadecyl)phosphinic acid

impurity 1

Reference substance name:

Octadecylphosphonic acid

EC Number:

225-216-4

EC Name:

Octadecylphosphonic acid

Cas Number:

4724-47-4

Molecular formula:

C18H39O3P

IUPAC Name:

octadecylphosphonic acid

impurity 2

Reference substance name:

Dimethyl octadecylphosphonate

EC Number:

246-904-0

EC Name:

Dimethyl octadecylphosphonate

Cas Number:

25371-54-4

Molecular formula:

C20H43O3P

IUPAC Name:

dimethyl octadecylphosphonate

Test material form:

solid

Details on test material:

Test Item Identification: X#15249Batch: 04055A001Purity: >91%Description: White waxy solid blockStorage conditions: room temperature in the dark

Specific details on test material used for the study:

Test Item Identification: X#15249Batch: 04055A001Description: White waxy solid blockStorage conditions: room temperature in the dark

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: A mixed population of activated sewage sludge micro-organisms was obtained on 6 September 2005 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.- Preparation of Inoculum: The sample was washed two times by settlement and resuspension in mineral medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. The washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 °C and used on the day of collection. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the washed activated sewage sludge by suction through pre-weighed GF/A filter paper using a Buchner funnel (rinsed three times with 10 mL deionised reverse osmosis water prior to drying in an oven). Filtration was then continued for a further 3 minutes after rinsing the filter three successive times with 10 mL of deionised reverse osmosis water. The filter paper was then dried in an oven at approximately 105 °C for at least 1 hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 2.0 g/L prior to use.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

15.1 mg/L

Based on:

test mat.

Remarks:

equivalent to 10mgC/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

PRELIMINARY INVESTIGATIONAL WORKPreliminary investigational work determined that the substance was not soluble in water. Methods to improve solubility/dispersibility included ultrasonication, with & without heating to 65 C and high shear mixing, following ultrasonication and on its own. All methods formed a cloudy water column with large wax pieces of test material visible on the surface. As there was no difference in the observations made on the preparations between high shear mixing and ultrasonication, it was considered appropriate to use ultrasonication as a means to aid the dispersion of the test material.EXPERIMENTAL PREPARATION45.3 mg of test material was dispersed in 200 ml of culture medium and subjected to ultrasonification for 30 minutes. The volume was adjusted to 3 litres to give a final test item concentration of 15.1 mg/L, equivalent to 10 mg carbon/L. Inoculum control vessels were prepared with inoculated mineral medium and the vessels were adjusted to 3 litres with mineral media. The final concentration of suspended solids was 30 mg/L.STANDARD MATERIALSodium benzoate was used as the standard material. An initial stock solution of 1000 mg/L was prepared by dissolved the standard material directly in the culture medium. A 51.4 mL aliquot was added to the test vessel and diluted to give a final concentration of 17.1 mg/L or 10 mg carbon/L. The solution was inverted several times to ensure homogenity of the solution.TOXICITY CONTROLA toxicity control, containing the test and standard material, was prepared in order to assess any toxic effect of the test material on the sewage sludge micro-organisms.An aliquot (453.3 mg) of the test material stock solution was dispersed in 200 ml of cultured medium and subjected to ultrasonification for 30 minutes. An aliquot (51.4 mL) of sodium benzoate stock solution was also added to the test vessel. The volume was adjusted to 3 litres to give a final concentration of 15.1 mg test material/L plus 17.1 mg sodium benzoate/L, equivalent to a total of 20 mg carbon/L.PREPARATION OF TEST SYSTEMThe following preparations were made up and inoculated in 5 litre test culture vessels each containing 3 litres of solution:a) An inoculated control, in duplicate, consisting of inoculated mineral medium.b) The procedure control containing the reference material, in duplicate, in inoculated mineral medium to give a final concentration of 10 mg carbon/L.c) The test material, in duplicate, in inoculated mineral medium to give a final concentration of 10 mg carbon/L.d) The test and reference materials in inoculated mineral medium to give a final concentration of 20 mg carbon/L to act as toxicity control (one vessel only).Each test vessel was inoculated with the prepared inoculum at a final concentration of 2.5 mg suspended solids (ss)/L. The concentration of the suspended solids was determined by filtering a sample of washed activated sludge through pre-weighed GF/A filter paper and weighing the filter paper after drying in an oven at 105 oC for at least 1 hour. The test was carried out in a temperature controlled room at 22 ± 2 °C in darkness.Approximately 24 hours prior to addition of the test and reference materials, the vessels were filled with 2400 mL of mineral medium and 36 mL of inoculum and aerated overnight. On Day 0 the test and reference materials were added and the volume in all the vessels was adjusted to 3 litres by the addition of culture medium .The test vessels were sealed and CO2-free air bubbled through the solution at a rate of 40 mL/min per vessel and stirred continuously by magnetic stirrer.The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified de-gassed water.pH MEASUREMENTSThe pH of the test preparations was determined on day 28 prior to acidification with hydrochloric acid, using a WTW pH/Oxi 340I pH and dissolved oxygen meter.VALIDATION CRITERIA-The results are considered valid if, in the same test, the reference material yields 60 % degradation by day 14.-The test material may be considered to be readily biodegradable if ≥60 % degradation is attained within 28 days. This level of degradation must be reached within 10 days of biodegradation exceeding 10 %.-The toxicity control should attain ≥25 % degradation by day 14 for the test material to be considered as non-inhibitory.-The test is considered valid if the difference of the extremes of replicate values of production of CO2 is less than 20 %.-The total CO2 evolution in the control vessels at the end of the test should not normally exceed 40 mg/L medium-The IC content of the test material suspension in the mineral medium at the beginning of the test should be <5 % of the TC.

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Preliminary study:

The results obtained from the preliminary work proved the substance was not soluble in water.

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

43

Sampling time:

28 d

Remarks on result:

other: The pH values for the two replicates R1 and R2 were 7.6 and 7.7, respectively, on day 28.

Details on results:

The total CO2 evolution in the inoculum control vessels on day 28 was 23.06 mg/L, satisfying the validation criteria of the OECD guidelines. The IC/TC ratioof the test material in suspension in the mineral mdicium at the start of the test was below 5%, satisfying the validation criteria of the OECD guidelines.The toxicity control attained 56 % degradation after 14 days and 65 % degradation after 28 days thereby confirming that the test material was not toxic/ inhibitory to the sewage treatment micro-organisms used in the test.Sodium benzoate attained 62 % degradation after 14 days and 78 % degradation after 28 days thereby confirming the suitability of the inoculum and test conditions.The test material attainted 43% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms of OECD Guideline 301B.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

Under the conditions of this study, the test material attained 43 % degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD guideline 301B,.

Executive summary:

The ready biodegradability of the test material was assessed in accordance with the standardised guideline OECD 301B.

The test material, at a concentration of 10 mg Carbon/L, was exposed (in an aerobic aqueous medium) to activated sewage sludge microorganisms with mineral medium in sealed culture vessels in the dark at 21 °C for 28 days.

The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference material, sodium benzoate, together with a toxicity control were used for validation purposes.

Under the conditions of this study, the test material attained 43 % degradation after 28 days and therefore cannot be considered to be readily biodegradable u nder the strict terms and conditions of OECD guideline 301B.