Chlorodimethyloctylsilane

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 Jan - 31 Mar 2017

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:

Staatliches Gewerbeaufsichtsamt Hildesheim, Germany

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant, Hildesheim, Germany.
- Storage conditions and preparation of inoculum for exposure: The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was re-suspended in mineral salts medium and was maintained in an aerobic condition by aeration for 2 h. Thereafter the sludge was homogenized with a blender. After sedimentation the supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air for 7 d.
- Storage length: 7 d
- Concentration of sludge: Colony forming units (CFU) of the inoculum were determined prior to test start by standard dilution plate count: 1.47 x 10^9 CFU/L. The CFU concentration of the inoculum corresponds to approx. 1.47 x 10^7 CFU/L in the final test solution.

Duration of test (contact time):

60 d

Initial conc.:

21 mg/L

Based on:

test mat.

Initial conc.:

50.4 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F.
- Solubilising agent (type and concentration if used): The test item stock solution of 52.5 mg test item/ 5 mL silicone oil was prepared by weighing out of the test item in a GC-Vial and adding the necessary amount of silicone oil. The stock solution was vortexed until the test item was completely dissolved. 250 mL inoculated test medium were filled in the brown glass bottles of the test item replicates. 500 µL test item – silicone oil stock solution were pipetted directly into the inoculated test medium.
- Test temperature: 21.8 – 22.1 °C
- pH: 7.57 - 7.92 (at test start the pH-values of the prepared solutions in the measuring flasks (inoculum control and functional control) and the prepared solutions in the separate replicates (inoculum control with silicone oil, test item and toxicity control), were determined. At test end the pH-values of the test solutions in the brown glass bottles were determined.)
- Suspended solids concentration: 10 mL sludge/L were used to initiate inoculation.
- Continuous darkness: yes
- Other: continuous stirring

TEST SYSTEM
- Culturing apparatus: 500 mL brown glass bottles, with 250 mL test volume. The bottles were closed with OxiTop measuring heads.
- Number of culture flasks/concentration: 2
- Measuring equipment: OxiTop® measuring system (WTW)
- Details of trap for CO2 and volatile organics if used: A rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2.

SAMPLING
- Sampling method and frequency: The oxygen consumption was determined in the incubation vessels by the OxiTop® measuring system at 360 measuring points during the 60 d incubation period.

CONTROL AND BLANK SYSTEM
- Inoculum control: 2 (test medium without test and / or reference item)
- Inoculum control with silicone oil: 2 (test medium without test and / or reference item. 500 µL silicone oil was pipetted directly into the inoculated test medium)
- Functional control: 1 (test medium with reference item)
- Toxicity control: 1 (test and reference item as well as silicone oil)

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

25

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

34

Sampling time:

60 d

Results with reference substance:

The percentage degradation of the functional control reached the pass level of 60 % within 4 days.

BIOLOGICAL RESULTS:

Table 1: % biodegradation of test item, reference substance and reference substance in toxicity control within 60 d.

[d]	Biodegradation [%]
	Functional control	Test Item		Toxicity Control
	R1	P1	P2	T1
2	27	0	0	18
4	72	0	0	43
7	81	0	1	51
9	85	7	10	56
11	88	11	14	59
13	89	12	16	61
15	90	13	19	63
17	92	15	21	64
19	92	18	24	66
22	94	19	25	66
24	95	21	26	67
26	94	22	28	67
28	94	22	27	67
30	95	23	28	68
32	95	22	28	68
34	95	24	29	68
37	95	25	31	69
39	95	25	31	69
41	95	26	32	69
43	95	26	33	70
45	95	27	34	70
47	95	26	32	70
49	96	28	34	71
52	96	27	35	70
54	96	28	34	70
56	97	28	34	70
58	97	29	36	71
60	98	31	37	71

VALIDITY CRITERIA:

- The percentage degradation of the functional control reached the pass level of 60 % within 4 days (validity criterion: 60 % after 14 days).

- The mean oxygen depletion in the inoculum control was 13.7 mg O2/L on day 28 and 19.1 mg O2/L on day 60 (validity criterion: < 60 mg oxygen/L).

- The mean oxygen depletion in the inoculum control with silicone oil was 13.0 mg O2/L on day 28 and on day 60 16.9 mg O2/L.

- The pH-value of all test replicates was in the range of 6.0 - 8.5 at the end of the test.

- The difference of extremes of replicate values of removal of the test item at the end of the test was less than 20 % (5% difference on day 28 and 6% on day 60).

- The percentage degradation of the toxicity control reached the pass level of 25 % within 4 days (validity criterion: 25 % after 14 days).

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:

A biodegradation study according to OECD 301F resulted in a biodegradation of 25% after 28 d and 34% after 60 d.

Description of key information

Not readily biodegradable (25% after 28 d and 34% after 60 d, OECD 301F)

Additional information

One study is available (2017) investigating the biodegradation of the substance and was performed according to OECD guidance 301F and GLP. The inoculum (non-adapted activated sludge from a sewage treatment plant) was exposed for 60 days to 21 mg/L test substance (50.4 mg/L ThOD) and biodegradation was calculated based on O2 consumption. Silicone oil was used as a solubilizing agent. An inoculum control, an inoculum control with silicone oil, a functional control and a toxicity control were run in parallel. The substance reached a biodegradation value of 25% after 28 d and 34% after 60 d. The percentage degradation of the functional control reached the pass level of 60% within 4 days while the toxicity control reached the pass level of 25% biodegradation within 4 days. Therefore, the substance is not considered readily biodegradable and not inhibitory to activated sludge microorganisms.