Butyltris[(2-ethyl-1-oxohexyl)oxy]stannane

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:

4 October 2001 to 1 November 2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant, D-31137 Hildesheim.
- Activated sludge from the sewage plant at Hildesheim is well suited as it comprises mostly municipal sewage and hardly any industrial chemical waste.
- Laboratory culture: The activated sludge was filtered with folded filter. The first 200 mL of the filtrate were not used. The second filtrate effluent from the domestic waste water was used to initiate inoculation.
- Colony forming units in the test vessels: 10^4 - 10^6 CFU/L

Duration of test (contact time):

28 d

Initial conc.:

6 mg/L

Based on:

test mat.

Initial conc.:

8.91 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral nutrient solution according to OECD 301 D
- Test temperature: 20 - 21 °C
- pH: 6.93 - 7.11 at the beginning of the test, 5.05 - 6.65 at the end.
- pH adjusted: no
- Aeration of dilution water: One day before the test started the demineralised water for the test medium was aerated until oxygen saturation and then left at room temperature for at least 20 h.
- Suspended solids concentration: 10^4 - 10^6 CFU/L

TEST SYSTEM
- Culturing apparatus: BOD bottles with glass stoppers (volume 300 mL)
- Number of culture flasks/concentration: 10
- The following test solutions were prepared in the BOD bottles as incubation vessels: 5 x 2 incubation vessels for the test compound (P1, P2), 5 x 2 incubation vessels for the functional control (R1, R2) and 5 x 2 incubation vessels for the toxicity control (T1, T2). The test series was accompanied by a complete parallel series for the determination of the oxygen demand of the inoculated control medium (C1, C2).
- All test solutions were made as stock solutions. 0.2 mL of the inoculum was given in each BOD bottle. The stock solutions were filled to the BOD bottles with a siphon. The incubation vessels were closed without air bladders.
- Dispersion treatment: Agitation
- Measuring equipment: pH-Meter, "CORNING" pH 240 and Oximeter, "WTW" Oxi 530.

SAMPLING
- The oxygen concentration was measured in the incubation vessels on day 0, 7, 14, 21 and 28.
- The temperature in the incubator was documented once every working day. At the beginning and at the end of the test the pH value of the solutions was determined.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Nutrient solution and inoculum
- Functional control: Reference material and inoculum
- Toxicity control: 3.0 mg/L test material + 5.0 mg/L reference material (sodium acetate) + nutrient solution and inoculum

EVALUATION OF THE DATA
For the calculation of the BODn and the biodegradation of the test material, functional control and toxicity control the oxygen depletion of the control was taken into account.
- Calculation of the theoretical oxygen demand (ThOD) of the reference material according to Formula (1): ThOD = [(16.(2c + ½ . (h – cl – 3n) +3s + 5/2p + ½ na – o)) / MW]
MW = Molecular weight reference material, respectively
Concerning the OECD-guideline 301D the index of the atoms of the material example CcHhClclNnNanaOoPpSs was used for the calculation of the ThOD.

- Calculation of the biological oxygen demand (BOD) according to Formula (2): BOD [mg O2/L] = (mt0 – mtx) – (mb0 – mbx)

- Calculation of the biodegradation according to Formula (3): Biodegradation [%] = ( BOD [mg O2/L] / (ThOD / COD [mg O2/L]) ) x 100

COD = chemical oxygen demand of the test material
ThOD = theoretical oxygen demand
mt0 = O2-concentration of the material on day 0
mtx = O2-concentration of the test material on day x
mb0 = O2-concentration of the inoculum control on day 0
mbx = O2-concentration of the inoculum control on day x

VALIDITY OF THE TEST
- The percentage degradation of the functional control must reach the pass level of 60% by day 14.
- The oxygen depletion in the inoculum control should not exceed 1.5 mg O2/L after 28 d.
- The residual concentration of oxygen in the test bottles should not fall below 0.5 mg/L at any time.
- The difference of extremes of replicate values of removal of the test material at the end of the test, at the plateau or at the end of the 10-d-window as appropriate must be less than 20%, if the test material is readily biodegradable.
- If in the toxicity test containing both test material and reference material, less than 25% degradation occurred within 14 days, the test can be considered to be inhibitory.

Reference substance:

acetic acid, sodium salt

Test performance:

Validity Criteria
The validity criteria were fulfilled according to the OECD 301D guideline:
- The percentage degradation of the functional control reached the pass level of ≥ 60 % after 14 days.
- The oxygen depletion in the inoculum control came to 1.73 mg dissolved oxygen/L after 28 days.
- The residual concentration of oxygen in the test bottles did not fall below 0.5 mg/L at any time.
- The difference of extremes of replicate values of removal of the test material at the end of the test was less than 20 %.
- The percentage degradation of the toxicity control reached the pass level of 25 % after 14 days.

Key result

Parameter:

% degradation (O2 consumption)

Value:

56

Sampling time:

28 d

Details on results:

Chemical oxygen demand
- The determined COD of 1.485 mg O2/mg test material was used for calculation of BOD and biodegradation in %.

Results of the inoculum control
- The oxygen demand in the inoculum control came to 1.73 mg O2/L after 28 days.
- The slightly higher oxygen demand in the inoculum control after 28 days had no impact on quality and integrity of the study.

Results of the functional control
- The pass level of a biodegradation > 60% was reached after 5 days. The validity criterion that the degradation should be > 60% after 14 days was fulfilled.

Results of the test material
- The test material reached the pass level of 10% (beginning of biodegradation) after an adaptation phase of 1 day. The residual concentration of oxygen in the test bottles was a mean of 2.57 mg O2/L.

Results of the toxicity control
- In the toxicity control the degradation achieved 69% after 14 days. The biodegradation of the reference material was not inhibited by the test material.

Course and stages of biodegradation of reference and test material
- In the case of the functional control, the adaptation phase transformed to a degradation phase after 1 day (degradation > 10%). The pass level > 60% was reached after 5 days. After 21 days a maximum rate of 88% and the plateau was reached.
- The biodegradation rate of the toxicity control came to 69% after 14 days. The biodegradation of the reference material was not inhibited by the test material.
- The test material reached the 10% level (beginning of degradation) after 1 day. The biodegradation came to 54% after 14 days and to a maximum of 60% after 21 days. The pass level of a biodegradation of > 60% was not reached in the 10-d-window but after 21 days.
- The test material must be regarded to be not readily biodegradable in the 10-d-window.

Water parameter
- The water parameters of the nutrient medium (stock solution No. 1) and the demineralised water were measured before the test began. The pH values of the samples were measured at test beginning and test end.

Results with reference substance:

The pass level of a biodegradation > 60% was reached after 5 days. The validity criterion that the degradation should be > 60% after 14 days was fulfilled.

Table 1: Oxygen Determination of the Inoculum Control and Functional Control

Study Day	Inoculum Control				Functional Control 10 mg/L ThOD 0.78 mg O2/mg
	O2 (mg/L)				O2 [mg/L]			BOD		Degradation
	C1	C2	mean	O2-depletion	R1	R2	mean	[mg O2/L]	[mg O2/mg]	[%]
0	9.39	9.43	9.41	-	9.26	9.37	9.32	-	-	-
7	8.42	8.57	8.50	0.91	2.00	2.01	2.01	6.40	0.64	82
14	8.06	7.96	8.01	1.40	1.22	1.36	1.29	6.63	0.66	85
21	8.18	8.16	8.17	1.24	1.21	1.23	1.22	6.86	0.69	88
28	7.83	7.53	7.68	1.73	1.00	0.66	0.83	6.76	0.68	87

 

Table 2: Oxygen Determination of the Test Material and Toxicity Control

Study Day	Test Material						Toxicity Control 3.0 mg/L Test Material + 5 mg/L Reference Material ThOD 1.044 mg O2/mg
	O2 [mg/L]			BOD		Degradation [%]	O2 [mg/L]			BOD		Degradation
	P1	P2	mean	[mg O2/L]	[mg O2/mg]		T1	T2	mean	[mg O2/L]	[mg O2/mg]	[%]
0	9.34	9.18	9.26	-	-	-	9.32	9.31	9.32	-	-	-
7	3.63	3.37	3.50	4.85	0.81	55	3.65	3.02	3.34	5.07	0.63	60
14	(0.19)	3.08	3.08	4.78	0.80	54	2.16	2.10	2.13	5.79	0.72	69
21	2.79	2.57	2.68	5.34	0.89	60	2.17	1.82	2.00	6.08	0.76	73
28	2.55	2.59	2.57	4.96	0.83	56	0.83	1.45	1.14	6.45	0.81	78

( ) = outlier, not included in calculations

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Under the conditions of this study the test material was not considered to be readily biodegradable.

Executive summary:

The ready biodegradability of the test material was investigated in accordance with the standardised guideline OECD 301 D, under GLP conditions.

The ready biodegradability in the Closed Bottle Test was determined with a non adapted activated sludge for the test material over 28 days.

The test material concentration selected as appropriate was 6.0 mg/L, corresponding to a COD of 1.485 mg O2/mg test material and 8.91 mg O2/L in the test vessel. The degradation was followed by measuring the oxygen concentrations.

The oxygen concentration was depleted by the respiration of bacteria. The biodegradation is therefore expressed as the percentage BOD and was calculated for each oxygen analysis. The oxygen depletion in the inoculum control came to 1. 73 mg O2/L after 28 days. The residual concentration of oxygen in the test bottles did not fall below 0.5 mg/L at any time. In order to check the activity of the study system sodium acetate was used as functional control. The functional control reached the pass level > 60% after 5 days. After 14 days a biodegradation rate of 85% was reached. In the toxicity control containing both test and reference material 69% degradation occurred within 14 days. The biodegradation came to a maximum of 78% after 28 days. The degradation of the reference material was not inhibited by the test material.

The test material reached the 10% level (beginning of degradation) after 1 day. The biodegradation came to 54% after 14 days and to a maximum of 60% after 21 days. The pass level of a biodegradation of ≥ 60% was not reached in the 10-day window but after 21 days.

Under the conditions of this study the test material was not considered to be readily biodegradable.

Description of key information

Under the conditions of this study the test material was not considered to be readily biodegradable.

Additional information

The ready biodegradability of the test material was investigated in accordance with the standardised guideline OECD 301 D, under GLP conditions.

The ready biodegradability in the Closed Bottle Test was determined with a non adapted activated sludge for the test material over 28 days.

The test material concentration selected as appropriate was 6.0 mg/L, corresponding to a COD of 1.485 mg O2/mg test material and 8.91 mg O2/L in the test vessel. The degradation was followed by measuring the oxygen concentrations.

The oxygen concentration was depleted by the respiration of bacteria. The biodegradation is therefore expressed as the percentage BOD and was calculated for each oxygen analysis. The oxygen depletion in the inoculum control came to 1. 73 mg O2/L after 28 days. The residual concentration of oxygen in the test bottles did not fall below 0.5 mg/L at any time. In order to check the activity of the study system sodium acetate was used as functional control. The functional control reached the pass level > 60% after 5 days. After 14 days a biodegradation rate of 85% was reached. In the toxicity control containing both test and reference material 69% degradation occurred within 14 days. The biodegradation came to a maximum of 78% after 28 days. The degradation of the reference material was not inhibited by the test material.

The test material reached the 10% level (beginning of degradation) after 1 day. The biodegradation came to 54% after 14 days and to a maximum of 60% after 21 days. The pass level of a biodegradation of ≥ 60% was not reached in the 10-day window but after 21 days.

Under the conditions of this study the test material was not considered to be readily biodegradable.