Amides, C8-18(even-numbered) and C18(unsatd.), N-(2-hydroxypropyl)

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:

From November 02, 2005 to December 01, 2005

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

The study with the test substance was conducted according to ISO Guideline 14593 and can be considered comparable to a reduced version of OECD Guideline B. The following validity criteria of the OECD guideline were not met: 1. Inorganic carbon analysis done only on Day 28 for both reference and test substances, therefore the course of biodegradation was not followed throughout the study. 2. Toxicity control not used and no information was provided on inhibition of inoculum by the test substance.

Qualifier:

equivalent or similar to guideline

Guideline:

ISO 14593:1999 (Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium - Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test))

Deviations:

yes

Remarks:

A reduced version of the test was performed, as a screening test, with inorganic carbon analysis on Day 28 only.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Secondary effluent, from a laboratory treatment unit treating sewage from Newton Abbot sewage treatment works
- Pretreatment: On the day of the test the effluent was filtered and sparged with CO2 free air for at least 2 h at pH 6.5 ± 0.2, to remove any dissolved
carbon dioxide. After this time the effluent was neutralised, to pH 7.0 ± 0.2, and allowed to stand for 1 h.
- Concentration: 10 % of the final volume of test bottles
- Water filtered: Yes
- Type and size of filter used, if any: Whatman G/FC filter paper

Duration of test (contact time):

ca. 28 d

Initial conc.:

ca. 19 mg/L

Based on:

ThIC

Parameter followed for biodegradation estimation:

inorg. C analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: 85 mg of KH2PO4, 217.5 mg of K2HPO4, 334 mg of Na2HPO4.2H2O, 5 mg of NH4CI, 22.5 mg of MgSO4.7H2O, 36.4 mg of CaCl2.2H2O and 0.25 mg of FeCl3.6H2O per litre of deionised water
- Test temperature: 22 ± 2 °C
- pH: Initial - 7.0 ± 0.2; Final - 6.9 in the inoculum blank bottle, 6.6 in the reference substance bottle and 6.7 in the test material bottle.
- pH adjusted: Yes (initially)
- Other: Continuous shaking of bottles in orbital incubator

TEST SYSTEM
- Culturing apparatus: Septum sealed bottles with a nominal volume of 125 mL (each filled with 95 mL inoculated mineral medium, and made up to
100 mL with test or reference substance solution and/or water as applicable)
- Number of culture flasks/concentration: Triplicate bottles of each set (blank, reference and test bottles). Additional triplicate blank and reference substance test bottles for TOC analysis
- Measuring equipment and method: 1 mL of 10 M sodium hydroxide solution was added to the appropriate test bottles, and shaken for at least 1 h. Inorganic carbon (IC) was then measured using a Dohrman DC-190 carbon analyser. For IC analysis, this instrument acidifies the sample with 20 % phosphoric acid, purges with carrier gas oxygen (carbon dioxide free) and quantifies the resulting gas for entrained carbon dioxide using a non-dispersive infra-red detector.
- Test performed in closed vessels: Yes
- Other: TOC was analysed only for reference. The low solubility of test material made TOC analysis impractical.

SAMPLING
- Sampling frequency: Triplicate bottles of each set sacrificed at the end of the study (Day 28). Additional triplicate blank and reference substance test bottles were also sacrificed on Day 0 and were analysed for TOC.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

Reference substance:

benzoic acid, sodium salt

Remarks:

Theoretical carbon concentration: 58 %; concentration used: 20 mg carbon/L (nominal)

Test performance:

None

Key result

Parameter:

% degradation (inorg. C analysis)

Value:

ca. 74

St. dev.:

6.51

Sampling time:

28 d

Results with reference substance:

Reference substance attained a maximum level of biodegradation (based on evolved carbon dioxide) of 104 %. This is over 60 % degradation, as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms (See table 1 for details).

Table 1. Results of CO2 headspace biodegradability test

	Blank	Reference substance	Test substance^#
Day 0 stock solution TOC (mg/L)	-	378	-
Day 0 test bottles TOC (mg/L)	3.04	21.8	-
	3.65	22.7	-
	2.45	9.31*	-
Mean (mg/L)	3.05	22.3**	-
Standard deviation	0.60	-**	-
Day 28 test bottles IC (mg/L)	2.30	24.8	15.5
	2.44	26.6	17.0
	3.85	26.7	18.1
Mean (mg/L)	2.86	26.0	16.9
Standard deviation	0.86	1.07	1.31
Biodegradation*** (%)	-	98	67
	-	106	74
	-	107	80
Mean (%)	-	104	74
Standard deviation	-	4.93	6.51

*Anomalous value, not included in mean

**Mean calculated on two values only; standard deviation not calculated

***Biodegradation = (IC concentration in test bottle – Mean IC concentration in control) x 100 / Initial TOC in test bottle

^#No Day 0 TOC measurements were made, due to the low aqueous solubility test material, so the nominal concentration of 19 mg C/L was used.

Validity criteria fulfilled:

not specified

Interpretation of results:

readily biodegradable

Conclusions:

Under the study conditions, the test substance was degraded by 74% after 28 d and was therefore considered to be readily biodegradable.

Executive summary:

A study was conducted to determine the ready biodegradability of the test substance, C8-18 and C18-unsatd. MIPA, in the CO2 headspace test based on ISO Guideline 14593, in compliance with GLP. A reduced version of the test was performed, with inorganic carbon analysis on Day 28 only. A solution of the test substance in a mineral medium, corresponding to 19 mg carbon/L (nominal), was inoculated with secondary sewage effluent in septum sealed bottles, then shaken for 28 days. The reference material used was sodium benzoate at a concentration of 20 mg carbon /L (nominal). Sufficient bottles were prepared to allow triplicate samples of each set (blank, reference and test bottles) to be sacrificed at the end of the study. CO2 generated as a result of mineralisation of organic carbon arising from biodegradation was then measured using a Dohrman DC-190 carbon analyser. Triplicate blank and reference substance test bottles were also collected on Day 0 and analysed for total organic carbon (TOC). TOC was not determined for the test substance because of low solubility. The reference substance attained a maximum level of biodegradation (based on evolved CO2) of 104%. This is over 60% degradation, as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms. Under the study conditions, the test substance was degraded by 74% after 28 d and was therefore considered to be readily biodegradable (Daniel, 2006).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

A study was conducted to determine the ready biodegradability of the test substance, C8-18 and C18-unsatd. MIPA, in the CO2 headspace test based on ISO Guideline 14593, in compliance with GLP. A reduced version of the test was performed with inorganic carbon analysis on Day 28 only. A solution of the test substance in a mineral medium, corresponding to 19 mg carbon/L (nominal), was inoculated with secondary sewage effluent in septum sealed bottles, then shaken for 28 days. The reference material used was sodium benzoate at a concentration of 20 mg carbon /L (nominal). Sufficient bottles were prepared to allow triplicate samples of each set (blank, reference and test bottles) to be sacrificed at the end of the study. CO2 generated as a result of mineralisation of organic carbon arising from biodegradation was then measured using a Dohrman DC-190 carbon analyser. Triplicate blank and reference substance test bottles were also collected on Day 0 and analysed for total organic carbon (TOC). TOC was not determined for the test substance because of low solubility. The reference substance attained a maximum level of biodegradation (based on evolved CO2) of 104%. This is over 60% degradation, as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms. Under the study conditions, the test substance was degraded by 74% after 28 d and was therefore considered to be readily biodegradable (Daniel, 2006).