Trimethoxypropylsilane

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:

1994-08-31 to 1994-11-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of activated sludge: Marl-Ost municipal sewage treatment plant, The sewage sludge was sampled on 1994-09-07.
- Storage conditions: The determination of suspended solids was carried out before the inoculum. During this time the sludge had to be aerated by aerating tube.
- Preparation of inoculum for exposure: The sludge was centrifuged for 15 min at 3000 rpm. The supernatant was then discarded and the sludge resuspended in mineral medium (washing step). After repeated centrifugation, the sludge was resuspended.
- Concentration of sludge: 3.45 g/L dry matter
- Initial cell/biomass concentration: Inoculum was added to the test batches at a dry matter of content 27.6 mg/L

Duration of test (contact time):

28 d

Initial conc.:

13.33 mg/L

Based on:

DOC

Remarks:

after 3 h in test batch

Initial conc.:

11.28 mg/L

Based on:

DOC

Remarks:

after 3 h in control batch

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

Vessels: 2000 ml conial flasks with loose aluminium foil closure

Test batches:
2 flasks containing test substance (11.2 mg DOC/l after 3h) and inoculum
2 flasks without test substance, but with inoculum (= blank batch)
2 flasks containing control subsatnce (sodium benzoate: 10.8 mg DOC/l after 3 hours) and inoculum

Method:
Addition of inoculum corresponding a dry matter content of 27.6 mg/test medium.
Filling up with about 2 l mineral medium
30 ml/l test substance stock solution, respectively 20 ml/l control substance stock solution, were given into the test vessels from which the test and control substance batches were filled up.
The content of substances was in mean value 13.33 mg DOC/l (after 3h) in the test batches, respectively 11.28 mg DOC/l (after 3 h) in the control batches.
The batches were filled up to 2.5 l with mineral medium.
From this batches two times 1000 ml were given into 2000 ml Erlenmeyer flasks.
The loosely covered flasks were incubated at 21.9 to 22.2 °C in the dark on a mechanical shaker for 28 days.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

50

Sampling time:

7 d

Parameter:

% degradation (DOC removal)

Value:

55

Sampling time:

14 d

Parameter:

% degradation (DOC removal)

Value:

54

Sampling time:

21 d

Parameter:

% degradation (DOC removal)

Value:

55

Sampling time:

27 d

Parameter:

% degradation (DOC removal)

Value:

54

Sampling time:

28 d

Details on results:

Results with reference substance:
98% DOC decrease after 7 days
99% DOC decrease after 14 days
100% DOC decrease after 21 days
99% DOC decrease after 27 days
99% DOC decrease after 28 days

DOC measurements of the test item

 

	DOC concentration after n days (mg/l)
	Flask no.		O h (C0)	3h (C3)	7	14	21	27	28
Test batches (Mineral medium + test item + inoculum)	1	a1	13.58	13.59	7.53	6.16	6.43	6.78	6.83
		a2	13.32	14.13	7.41	6.31	6.43	7.02	6.74
		Ca (t) = (a1 + a2) /2	13.45	13.86	7.47	6.24	6.43	6.90	6.79
	2	b1	12.25	13.78	7.04	6.74	6.62	6.28	6.61
		b2	12.30	13.38	7.00	6.77	6.67	6.37	6.80
		Cb (t) = (b1+ b2) /2	12.28	13.58	7.02	6.76	6.65	6.33	6.71
Blank batches (Mineral medium + inoculum)	1	c1	0.52	0.36	0.61	0.50	0.43	0.60	0.62
		c2	0.56	0.39	0.54	0.44	0.42	0.65	0.62
		Cc (t) = (c1 + c2) /2	0.54	0.38	0.58	0.47	0.43	0.63	0.62
	2	d1	0.49	0.36	0.70	0.53	0.49	0.60	0,62
		d2	0.44	0.41	0.68	0.49	0.49	0.61	0.59
		Cd (t) 0 (d1 + d2) /2	0.47	0.39	0.69	0.51	0.49	0.61	0.61
	Cbl(t)=Cc(t)+Cd(t)/2		0.51	0.39	0.64	0.49	0.46	0.62	0.62

 

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

A biodegradation result of 54% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

54% in 28 days (EU Method C.4-A)

Additional information

Trimethoxypropylsilane hydrolyses rapidly to propylsilantriol and methanol. The degradation observed in the biodegradation test is likely to be due to the degradation of methanol, which is expected to biodegrade rapidly and makes up 3 out of the 6 carbons in the molecule. Propylsilanetriol is not expected to biodegrade to any significant extent. A biodegradation result of 54% in 28 days was determined in a reliable study conducted according to EU method C.4 -A and in compliance with GLP.