Octadecan-1-ol, ethoxylated, phosphates

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:

1 October 2018 to 7 March 2019

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

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Purity: 100% (UVCB)
Appearance/Physical state: Solid, white pastille
Storage: Room temperature in the dark

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

A mixed population of activated sewage sludge micro-organisms was obtained on 5 November 2018 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.

Sewage sludge/treatment micro-organisms were selected following the recommendations of guidelines. Pre-adaption of the inoculum was not performed.

The activated sewage sludge sample was washed twice by settlement and re-suspension 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 deg. 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. Filtration was then continued for a further 3 minutes after rinsing the filter three successive times with 10 mL of deionized reverse osmosis water. The filter paper was then dried in an oven at approximately 105 deg. C for at least 1 hour and allowed to cool before weighing. This process was repeated until two successive dry weights were within 4%, thereby indicating that complete dryness had been attained. The suspended solids concentration was equal to 2.4 g/L prior to use.

Duration of test (contact time):

ca. 29 d

Initial conc.:

ca. 10 other: mg Carbon/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Preliminary solubility/dispersibility work was performed in order to determine the most suitable method of preparation.

From the preliminary solubility work and following the recommendations of the International Standards Organisation (ISO 10634, (1995)) it was concluded that the best testable dispersion was obtained when using the high shear mixing method of preparation.

The test item was dispersed directly in mineral medium.

An amount of test item (45.3 mg) was dispersed in approximately 400 mL of mineral medium with the aid of high shear mixing (approximately 7500 rpm, 15 minutes) prior to dispersal in inoculated mineral medium. The volume was adjusted to 3 liters to give a final concentration of 15.1 mg/L, equivalent to 10 mg carbon/L.

A test concentration of 10 mg carbon/L was employed in the test following the recommendations of the Test Guidelines.

Reference substance:

other: Sodium benzoate

Preliminary study:

From the preliminary solubility work and following the recommendations of the International Standards Organisation (ISO 10634, (1995)) it was concluded that the best testable dispersion was found to be when using the high shear mixing method of preparation.

Test performance:

The averaged total CO2 evolution in the two inoculum control vessels on Day 28 was 27.97 mg/L and therefore satisfied the validation criterion given in the OECD Test Guidelines.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

30

Sampling time:

28 d

Details on results:

Acidification of the test vessels on Day 28 followed by the final analyses on Day 29 was conducted according to the methods specified in the test guidelines. This acidification effectively kills the micro-organisms present and drives off any dissolved CO2 present in the test vessels. Therefore any additional CO2 detected in the Day 29 samples originated from dissolved CO2 that was present in the test vessels on Day 28 and hence the biodegradation value calculated from the Day 29 analyses is taken as being the final biodegradation value for the test item.

The results of the inorganic carbon analysis of samples from the first absorber vessels on Day 29 showed an increase in all replicate vessels with the exception of inoculum control Replicate 1 and test item Replicate 2.

The IC analysis of the samples from the second absorber vessels on Day 29 confirmed that no significant carry-over of CO2 into the second absorber vessels occurred.

Results with reference substance:

Sodium benzoate attained 67% biodegradation after 14 days and 80% biodegradation after 28 days. Greater than 60% degradation was attained within the 10-day window. These results confirmed the suitability of the inoculum and test conditions and satisfied the validation criterion given in the OECD Test Guidelines.

Statistical analysis of the Day 29 IC values for the inoculum control and test item vessels were not performed as this was considered not necessary as the test item obtained significantly greater IC values than the inoculum control vessels.

The toxicity control attained 64% biodegradation after 14 days and 66% biodegradation after 28 days thereby confirming that the test item did not exhibit an inhibitory effect on the sewage treatment micro-organisms used in the test.

Percentage Biodegradation Values

Day	% Biodegradation
	Procedure Control	Test Item	Toxicity Control
0	0	0	0
2	50	10	32
6	60	22	49
8	64	22	60
10	66	31	60
14	67	28	64
21	70	29	69
28	73	28	62
29*	80	30	66

* Day 29 values corrected toinclude carry-over of CO2 detected in Absorber 2, if any.

 

 

All validation criteria were met for this study.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

In a study conducted according to OECD 301 B the test item attained 30% biodegradation after 28 days and therefore cannot be considered
to be readily biodegradable.

Executive summary:

The test item attained 30% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B. Sodium benzoate attained 67% biodegradation after 14 days with greater than 60% degradation being attained in a 10-day window. These results confirmed the suitability of the inoculum and test conditions and satisfied the validation criterion given in the OECD Test Guidelines.

Description of key information

In a study conducted according to OECD 301 B the test item attained 30% biodegradation after 28 days and therefore cannot be considered

to be readily biodegradable.