Fatty acids, montan-wax, stearyl 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:

30 Mar - 27 Apr 2018

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)

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Remarks:

Manufacturing Industries Bureau, Ministry of Economy, Trade and Industry, Japan (22 Dec 2016)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Aerobic reactor of a Kurume central sewage treatment center (Kurume, Fukuoka, Japan) receiving predominantly domestic sewage (30 Mar 2018)
- Storage conditions: Aeration at about 22 °C
- Storage length: 3.5 h
- Concentration of sludge: 2810 mg/L as concentration of suspended solids
- Initial cell/biomass concentration: 30 mg/L as concentration of suspended solids

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium
- Solubilising agent: 0.5 g silica gel 60 (Nacalai Tesque, column chromatography grade) per test vessel
- Test temperature: 22 ± 1 °C
- pH: Measurement of the pH of the test solutions was not performed at the moment of preparation because the test item does not dissolve at 30 mg/L in water.
- pH adjusted: No (except mineral medium, adjusted to pH 7.4)
- Suspended solids concentration: 30 mg/L
- Continuous darkness: Yes
- Volume of test solution: 300 mL

TEST SYSTEM
- Culturing apparatus: Closed system oxygen consumption measuring apparatus for the measurement of the biochemical oxygen demand (BOD)
- Number of culture flasks/concentration: 2
- Measuring equipment: Closed system oxygen consumption measuring apparatus for the measurement of the biochemical oxygen demand (BOD)
- Details of trap for CO2: Soda lime No. 1 (Wako Pure Chemical Industries)
- Other: Every test solution was stirred with a stirrer.
- Preparation of test solutions: In each test vessel, an appropriate amount of accurately weighed test item (9 mg powder) was heated at 100 °C for 20 min in an oven. Then, 0.5 g silica gel 60 was added to each test vessel and stirred for 30 min with a stirrer at room temperature. Then, the mineral medium (the final volume of 300 mL minus the volume of activated sludge of 3.2 mL) was added to each test vessel so that the final test item concentration was 30 mg/L. The activated sludge was added to each test vessel after the addition of the mineral medium to a final concentrationof 30 mg/L suspended solids. Except for the heating step of the test vessels, the exact same procedure was followed for the preparation of the procedure control and inoculum blank (without test item).

SAMPLING
- Sampling frequency: The biochemical oxygen demand was measured continuously.
- Other: The appearances of the test solutions were observed daily and at the beginning and end of the test.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates consisting of test solution only.
- Procedure control: 1 replicate, consisting of activated sludge and sodium benzoate (reference compound)
- Toxicity control: 1 replicate consisting of 30 mg/L activated sludge (suspended solids), 30 mg/L test item and 100 mg/L sodium benzoate (reference compound)

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

28

Sampling time:

28 d

Remarks on result:

other:

Remarks:

average of two replicates

Details on results:

The average percentage biodegradation of the test item was 23% based on BOD at the end of the 10-d window.
The percentage biodegradation of the toxicity control was 58% based on BOD after 14 d, indicating that the substance is not toxic to activated sludge microorganisms at the tested concentration of 30 mg/L.

Results with reference substance:

The percentage biodegradation of the reference substance was 84% after 14 d based on BOD.

VALIDITY CRITERIA

The study fulfilled the validity criteria laid down by the guideline (Table 1).

 

Table 1: Validity criteria for OECD 301.

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	The difference of extremes of replicate values was 15%.	Yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	The percentage biodegradation of the reference compound was 84% after 14 d.	Yes
The toxicity control should degrade to at least 25% (based on ThOD or ThCO2) within 14 d.	The percentage biodegradation of the toxicity control was 58% after 14 d.	Yes
The oxygen uptake of the inoculum blank is normally 20-30 mg O2/L and should not be greater than 60 mg/L in 28 days.	The BOD of the control blank was 18 mg/L in 28 d.	Yes

 

 

BIODEGRADATION

The biodegradation results are summarized in Table 2.

 

Table 2. Percentage biodegradation by BOD.

Vessel		Day 7		Day 14		Day 21		Day 28		Average
		BOD [mg]	Deg [%]	BOD [mg]	Deg [%]	BOD [mg]	Deg [%]	BOD [mg]	Deg [%]
[1]	sludge + test item	5.5	6	8.6	14	10.1	19	10.8	20	28
[2]		7.4	13	11.5	25	13.5	31	15.0	35
[3]	sludge + sodium benzoate (procedure control)	41.8	76	46.5	84	48.4	87	49.3	88	-
[4]	sludge + test item + sodium benzoate (toxicity control)	42.7	50	49.9	58	55.0	64	57.6	67	-
[5]	control blank (inoculum blank)	4.0	-	4.8	-	5.1	-	5.3	-	-
[6]		3.6	-	4.4	-	4.9	-	5.3	-	-

 

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Interpretation of results:

not readily biodegradable

Conclusions:

The average biodegradation of the substance reached 28% after 28 d and was 23% at the end of the 10-d window. Therefore, the substance is not readily biodegradable according to OECD guideline criteria.

Description of key information

Not readily biodegradable (28% in 28 d, OECD 301 F)

Additional information

There is one GLP study available, in which the ready biodegradation of Fatty acids, montan-wax, stearyl esters (CAS 68308-30-5) was assessed according to OECD guideline 301 F.

The test item at a concentration of 30 mg/L was inoculated with 30 mg/L activated sludge (suspended solids) in a final volume of 300 mL mineral medium for 28 d in the dark. In addition, 0.5 g silica gel 60 was added to each test vessel. Biodegradation was followed by continuously measuring the biochemical oxygen demand with a closed system oxygen consumption measuring apparatus. A blank control, procedure control (reference substance) and toxicity control (test item + reference item) were run in parallel.

After 28 d, the average percentage biodegradation of the test item was 28% and 23% at the end of the 10-d window. The procedure control reached 84% biodegradation after 14 d, thus confirming the suitability of the inoculum and test conditions. The toxicity control attained 58% biodegradation after 14 d, indicating that the test item was not inhibitory to activated sludge microorganisms at the applied concentration level.

In conclusion, the test item is not readily biodegradable according to OECD guideline criteria.