Phosphoric acid, mono- and di-C16-18-alkyl esters

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:

5 February 2013 to 12 August 2013

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

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Laboratory culture: The activated sewage sludge 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 ºC and used on the day of collection.
- Water filtered: yes
- Type and size of filter used, if any: GF/A filter paper using a Buchner funnel

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Solution a KH2PO4 8.50 g/L, K2HPO4 21.75 g/L, Na2HPO4.2H2O 33.40 g/L, NH4Cl 0.50 g/L
Solution b CaCl2 27.50 g/L
Solution c MgSO4.7H2O 22.50 g/L
Solution d FeCl3.6H2O 0.25 g/L
To 1 liter (final volume) of purified water was added the following volumes of solutions a – d.
10 mL of Solution a
1 mL of Solution b
1 mL of Solution c
1 mL of Solution d
- Test temperature: approximately 21 ºC
- pH: 7.4 ± 0.2
- pH adjusted: yes, using diluted hydrochloric acid or sodium hydroxide solution
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 liter test culture vessels
- Method used to create aerobic conditions: The test vessels were sealed and CO2-free air bubbled through the solution at a rate of 30 to 100 mL/min per vessel and stirred continuously by magnetic stirrer.

SAMPLING
- Sampling frequency: Samples (2 mL) were taken from the first CO2 absorber vessels on Days 0, 2, 6, 8, 14, 17, 21, 28 and 29. The second absorber vessels were all sampled on Days 0 and 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: An inoculated control, in duplicate, consisting of inoculated mineral medium.
- Toxicity control: The test material plus sodium benzoate in inoculated mineral medium to give a final concentration of 20 mg carbon/L to act as a toxicity control (one vessel only).

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

20

Sampling time:

28 d

Details on results:

The test material attained 20% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.
The toxicity control attained 32% degradation after 14 days and 45% degradation after 28 days thereby confirming that the test material was not toxic to the sewage treatment micro-organisms used in the test.
Sodium benzoate attained 71% degradation after 14 days and 84% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The test material attained 20% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.

Description of key information

The test material attained 20% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater