Glycerol, propoxylated, esters with acrylic acid

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:

25 Mar - 23 Apr 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, Guideline study (OECD, etc.)

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 (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):
Not adapted activated sludge from the aeration tank of the ARA Werdhölzli (8048 Zürich, Switzerland), a municipal biological waste water treatment plant.
- Sampling: 23 March 2010, 11:00 a.m.
- Pretreatment: The activated sludge was used after sampling from the treatment plant without adaptation. However, the sludge was pre-conditioned for 2 days (aerated but not fed) to reduce the amount of CO2 produced by the blank controls.
Prior to the test the sludge was washed twice with tap water. After centrifugation the sludge, at a tenfold concentration of the final concentration to be achieved for the test, was suspended in test medium as described in Table 1 (see below).
- Concentration of sludge: 30 mg/l dry matter in the final mixture

Duration of test (contact time):

28 d

Initial conc.:

34 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

other: TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to OECD guideline
- Additional substrate: none
- Solubilising agent (type and concentration if used): none
- Test temperature: 22± 2 °C
- pH: 7.4± 0.2
- pH adjusted: yes (at beginning of test, with NaOH or HCl, if necessary)
- CEC (meq/100 g): no data
- Aeration of dilution water: aerated with CO2-free air
- Suspended solids concentration: 30 mg/l dry matter in the final mixture
- Continuous darkness: yes
- Other: Concentration of test substance and reference material: The test substance and reference material were applied by direct addition to give a final test concentration of about 20 mg/l with respect to the total organic carbon (TOC).

TEST SYSTEM
- Culturing apparatus: 2500 ml closed gas bottle
- Number of culture flasks/concentration: For each test series the following number of test flasks was set up: Test suspension containing inoculum, test medium and test substance (three replicates)
- Method used to create aerobic conditions: The test vessels were stirred thoroughly and aerated with synthetic CO2-free air
- Test performed in closed vessels due to significant volatility of test substance: -
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used: The air leaving the individual vessels was passed through gas-absorption bottles filled with KOH (125 ml of 0.13 M KOH).
- Other: -

SAMPLING
- Sampling frequency: The biodegradation of the test material was followed by CO2 measurements at frequent intervals to allow the assessment of the 10-d window (after 0, 1, 4, 7, 12, 14, 18, 21, 26, 28 days).
- Sampling method: not specified
- Sterility check if applicable: -
- Sample storage before analysis: -
- Other: -

CONTROL AND BLANK SYSTEM
- Inoculum blank: Inoculum blank containing inoculum and test medium (three replicates)
- Abiotic sterile control: Abiotic sterile control: containing test substance, test medium and 0.2 mM HgCl2 as sterilizing agent to prevent microbial decomposition (one replicate)
- Toxicity control: Toxicity control: containing inoculum + test medium + test substance + sodium benzoate as ready biodegradable reference compound (one replicate). In the toxicity control about 20 mg/l test substance and about 20 mg/l reference substance with respect to the total organic carbon (TOC) were tested as a mixture.
- Other: Procedure control: Procedure control containing inoculum, test medium and sodium benzoate as ready biodegradable reference compound (three replicates)

STATISTICAL METHODS: -

Reference substance:

benzoic acid, sodium salt

Remarks:

100% pure

Preliminary study:

not conducted.

Parameter:

% degradation (CO2 evolution)

Value:

72 - 85

Sampling time:

28 d

Remarks on result:

other: range of 2 replicates

Details on results:

Based on the data of the individual inorganic carbon determinations, the mean biodegradability in the CO2 Evolution Test of the test substance was calculated to be 79% (Table 2, Figure 1) after 28 days. The biodegradation of the test substance reached 60% at the end of the 10-d window. Significant biodegradation of the test substance was observed after a lag phase of about 7 days.

Results with reference substance:

The positive control, sodium benzoate, reached 100% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions (Table 3, Figure 2).

Table 2: CO₂produced by the test units, the inoculum blank and the corresponding degradation data.

	Inoculum	Test unit no. 1		Test unit no. 2
	blank *	containing test material		containing test material
	Total CO2	Total CO2		Total CO2		Mean
Time	release	release	Degradation	release	Degradation	Degradation
(days)	in test	in test	(%) **	in test	(%) **	of no. 1+2
	sample	sample		sample		(%)
	(mg IC/l)	(mg IC/l)		(mg IC/l)
0	0.0	0.0	0	0.0	0	0
1	-0.1	0.5	3	0.1	1	2
4	2.5	3.5	5	2.0	-2	1
7	4.8	6.5	8	4.5	-1	3
12	7.3	13.1	29	10.6	17	23
14	7.6	17.0	47	13.7	31	39
18	8.7	22.2	67	18.2	48	57
21	9.3	24.7	77	21.1	58	67
26	9.5	27.0	87	23.3	68	78
28	9.8	26.9	85	24.2	72	79
*	Mean of two replicates
**	The calculation is based on an organic carbon concentration
	in mg/l of	20.1	(Test unit no. 1)
		20.1	(Test unit no. 2)

Table 3: CO₂produced by the procedure control, the inoculum blank and the corresponding degradation data.

	Inoculum	Procedure control		Toxicity control (test		Abiotic
	blank *	(sodium benzoate)		material + sodium benzoate)		control
	Total CO2	Total CO2		Total CO2		Total CO2
Time	release	release	Degradation	release	Degradation	release
(days)	in test	in test	(%) **	in test	(%) ***	in test
	sample	sample		sample		sample
	(mg IC/l)	(mg IC/l)		(mg IC/l)		(mg IC/l)
0	0.0	0.0	0	0.0	0	0.0
1	-0.1	2.7	14	3.6	9	0.1
4	2.5	12.5	50	16.3	35	0.5
7	4.8	18.3	68	22.5	44	1.1
12	7.3	25.6	91	32.0	62	1.4
14	7.6	27.9	101	36.1	71	1.6
18	8.7	29.3	103	42.3	84	1.7
21	9.3	29.9	103	44.9	89	2.1
26	9.5	30.7	106	48.5	97	1.5
28	9.8	30.9	105	48.2	96	1.4
*	Mean of two replicates
**	The calculation is based on an organic carbon concentration in mg/l of					20.0
***	The calculation is based on an organic carbon concentration in mg/l of					40.1
	(sum of test substance and procedure control)

Results of additional controls:

Toxicity control

At the applied initial test concentration the test substance showed no significant toxic effect on the microbial population, since the biodegradation of the mixture (test substance + reference compound sodium benzoate) was within the expected theoretical value during thewhole test period (Table 3, Figure 2). The test was considered valid, since more than 25 % degradation occurred within 14 days.

Abiotic sterile control

The test substance

was not abiotically degraded (by processes producing CO₂) during the whole test period of 28 days in the absence of microorganisms as confirmed by the determinations of the inorganic carbon concentrations (Table 3).

Further remarks:

At the end of the test the pH value of both inoculum blanks and the procedure control was 7.4, respectively. The pH values of the test units and the toxicity control were 7.3 and 7.4, respectively.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test substance reached the pass level of 60% for ready biodegradability in the CO2 Evolution Test within the 10-d window and, therefore, can be termed as readily biodegradable.

Executive summary:

The biodegradability of the test substance exposed to microorganisms derived from the activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions.

The biodegradability - based on CO₂evolution - of the test substance was calculated to be79%of the theoretical value (ThCO₂) after an incubation time of 28 days.

The biodegradation of the test substance reached 60% at the end of the 10-d window.

Significant biodegradation of the test substance was observed after a lag phase of about 7 days.

The positive control, sodium benzoate, reached 100% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

The test substance reached the pass level of 60% for ready biodegradability in the CO₂Evolution Test within the 10-d window and, therefore, can be termed as readily biodegradable.

Description of key information

Biodegradation study- OECD  301B - 79% CO2 after 28 d (fulfilling the 10d-window) - readily biodegradable (PARAD consortium, BMG, 2010, BMG Engineering Ltd.)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Biodegradation study- OECD 301B - 79% CO2 after 28 d (fulfilling the 10d-window) - readily biodegradable (PARAD consortium, BMG, 2010, BMG Engineering Ltd.)

The biodegradability of the substance to be registered (test item) exposed to microorganisms derived from the activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions (PARAD consortium, BMG, 2010, BMG Engineering Ltd.). The biodegradability - based on CO₂evolution - of test item was calculated to be79%of the theoretical value (ThCO₂) after an incubation time of 28 days.The biodegradation of the test item reached 60% at the end of the 10-d window. Significant biodegradation of the test substance was observed after a lag phase of about 7 days. The positive control, sodium benzoate, reached 100% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.The test item reached the pass level of 60% for ready biodegradability in the CO₂Evolution Test within the 10-d window and, therefore, can be termed as readily biodegradable.

 

Since this study is the only study fulfilling the validity criteria, it is assigned to be key study.