Diethyl (hydroxymethyl)phosphonate

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:

key study

Study period:

2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Inoculum: A sample of final effluent that was collected on the day of the test from Thorndon Sewage
Treatment Works, a trickling-filter plant which treats predominantly domestic waste. It was
maintained under aerobic conditions in the laboratory, then, immediately before use, filtered
through glass wool (discarding the first 200 mL) and the filtrate used as the inoculum for the
test (1 mL filtrate/litre test medium).

Duration of test (contact time):

28 d

Initial conc.:

3 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Fourteen BOD bottles were filled with mineral salts medium inoculated with sewage effluent
(1 ml/L) and test substance at a concentration of 3.00 mg/L. Two further groups of fourteen
bottles were filled with mineral salts medium inoculated with sewage effluent (1 mL/L) with
and without sodium benzoate to act as control and reference bottles.
Additionally, a further four bottles were established for a concurrent five-day microbial inhibition assay,
in which the degradation of the readily degradable reference substance sodium benzoate was examined
in the presence of the test substance.
All bottles were incubated at 22 ± 2°C in darkness. Concentrations of dissolved oxygen (DO)
were measured in the duplicate bottles for the control, reference and test groups at the start of
the test and after 5, 7, 14, 21 and 28 days. DO concentrations in the duplicate bottles in the
inhibition assay were measured at the start of the test and at 5 days.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

Sodium benzoate degraded to 69% of its ThOD (1.67 mg O2/mg) after five days of incubation with a maximum of 84% at Day 28. In the presence of E06-16, sodium benzoate had been degraded to completion (100%) after five days. These results confirmed that the inoculum was viable and that the test substance was not inhibitory to the activity of the microbial inoculum.

Test performance:

See below

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

During the 28 days of the test, there was no noted oxygen consumption in bottles containing E06-16 alone. Substances are considered to be readily degradable in this test if oxygen consumption is equal to or greater than 60% of the theoretical value within ten days of the level exceeding 10%. E06-16 cannot, therefore, be considered to be readily degradable under the conditions of this test.

Results with reference substance:

Sodium benzoate degraded to 69% of its ThOD (1.67 mg O2/mg) after five days of incubation with a maximum of 84% at Day 28. In the presence of E06-16, sodium benzoate had been degraded to completion (100%) after five days. These results confirmed that the inoculum was viable and that the test substance was not inhibitory to the activity of the microbial inoculum.

not relevant

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

During the 28 days of the test, there was no noted oxygen consumption in bottles containing
E06-16 alone. Substances are considered to be readily degradable in this test if oxygen
consumption is equal to or greater than 60% of the theoretical value within ten days of the
level exceeding 10%. E06-16 cannot, therefore, be considered to be readily degradable under
the conditions of this test.

Executive summary:

The ready biodegradability of the test substance, E06-16, in an aerobic, aqueous medium was

assessed by monitoring the consumption of oxygen in closed bottles, containing the test

substance and an inoculum of sewage microorganisms, over a 28-day period. The amount of

oxygen taken up by the microbial population during biodegradation of the test substance,

is expressed as a percentage of theoretical oxygen demand (ThOD). The test is continued until the biodegradation curve has

reached a plateau for at least three determinations (observed over a maximum of 28 days).

During the 28 days of the test, there was no noted oxygen consumption in bottles containing

E06-16 alone.

As substances are considered to be readily degradable in this test if oxygen

consumption is equal to or greater than 60% of the theoretical value within ten days of the

level exceeding 10%, E06-16 cannot be considered readily degradable under the conditions of this test.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015

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)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
n/a

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, adapted

Details on inoculum:

A sample of activated sludge was obtained from Worlingworth sewage treatment works
(Suffolk, UK), which treats predominantly domestic waste. At the time of collection, the
sludge was sieved (1 mm2) then transported to the laboratory and aerated until required.
The concentration of suspended solids in a blended and homogenous sample was determined
before the start of the test. Aliquots (10 mL) of the sludge were filtered through dried and
pre-weighed Whatman GF/C filters in triplicate, which were then dried again at
approximately 108C for one hour, allowed to cool in a desiccator and reweighed. The
mixed liquor suspended solids (MLSS) content of the sludge was then determined and the
volume required to give a solids level of 30 mg/L in test cultures was calculated.

Duration of test (contact time):

28 d

Initial conc.:

50 other: mg O2/L

Based on:

ThOD/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

E06-16 was added to two bottles containing mineral salts medium inoculated with activated sludge (30 mg solids/L) to give a nominal test concentration of 50 mg O2/L. Two control
cultures contained inoculated mineral salts medium alone. Two cultures contained inoculated mineral salts medium plus the reference substance sodium benzoate (50 mg O2/L) of which one also contained E06-16 (50 mg O2/L) in order to assess the potential inhibitory effects of the test substance on the microbial inoculum. The test system comprised of an automated system for oxygen (O2) generation and the cultures were stirred and held in a thermostatically-controlled water bath.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

In the presence of E06-16 the degradation of the reference sodium benzoate achieved 64% after 3 days, indicating that the test substance was not inhibitory to the microbial inoculum.

Key result

Parameter:

% degradation (O2 consumption)

Value:

13

Sampling time:

28 d

Remarks on result:

other: 13% after 28 days

Details on results:

No significant degradation of E06-16 occured during the 28-d period.

Results with reference substance:

The rate of degradation of sodium benzoate was: 61% of its ThOD after 3 days. The cumulative amount of oxygen consumed by the control mixtures were: 52.84 and 40.98 mg O2/L.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Substances are considered to be readily biodegradable in this type of test if oxygen consumption is equal to or greater than 60% of the ThOD of the test mixtures within ten days of the consumption achieving 10%. Therefore, E06-16 was not considered to be readily biodegradable under the conditions of this test.

Executive summary:

E06-16 was not considered to be readily biodegradable under the conditions of this test.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater