Polysulfides, bis[3-(triethoxysilyl)propyl]

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 1999-06-15 to 1999-08-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Test method of new chemical substance, in Kanpogyo no. 5, Yakuhatsu No. 615 and 49 Kikyoku No. 392 1974

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

mixture of sewage, soil and natural water

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Sites for collection of sludge: collected from 10 sites nationwide in Japan: Fushikokawa sewage, Kashima sewage, Nakahama sewage, Ochiai sewage, Kitakamigawa river, Shinano river, Yoshino river, Lake Biwa, Hiroshima Bay, Doukai Bay. Date March 1999. The sewage sludge collected was returned sludge from sewage treatment plants. The river, lake, sea sludge was surface soil at boundary of beach contacting surface water and atmosphere.

- Mixing of fresh and old activated sludge: 5 l of an activated sludge cultivated for ca. 3 months and 5 l of the filtrate of mixture of sludge collected from the above sites were mixed to make 10 l.

- Method of cultivation: Approximately 30 min after stopping the aeration into the cultivating vessel, ca. a 1/3 of total supernatant liquid was removed. De-chlorinated water as added to the vessel to make a total volume of 10 l and the liquid in the vessels was aerated again for more than 30 min. 50 g/l of artificial sewage to 0.1 wt% in the added dechlorinated water. The same procedure was repeated once a day and activated sludge was provided after cultivating. Temperature of the cultivation was set at 25 ± 2 °C. Artificial sewage consisted of: glucose, peptone and potassium dihydrogen phosphate dissolved in dechlorinated water to adjust the concentration at 50 g/l and sodium hydroxide was added to adjust the pH to 7.0 ± 1.

- Preparation of inoculum for exposure: Before use, the activation level was checked with a standard substance.

- Concentration of sludge: 30 g/l.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS

- Composition of medium: 300 ml of cultivation medium, containing 1.91 ml of activated sludge was poured into test vessels and 30 mg of the test substance was added to the vessels to achieve nominal concentration of 100 mg/l.

- Test temperature: 25 ± 1 °C, measured daily.

- pH: 7

- pH adjusted: yes, culture medium and artificial sewage were adjusted to pH 7.

- Aeration of dilution water: yes

- Suspended solids concentration: 30 mg/l.

- Continuous darkness: not reported


TEST SYSTEM

- Culturing apparatus: 300 ml cultivation vessel (modified type).

- Number of culture flasks/concentration: three for test substance at 100 mg/l; one for reference; one for abiotic control; one for blank

- Test performed in closed vessels due to significant volatility of test substance: yes


SAMPLING

- Sampling frequency: BOD was continuously measured in the vessels. As a result of evidence of the production of ethanol and water soluble silicon in a preliminary test, after the cultivation period quantitative analysis was conducted on the test liquid for residual dissolved organic carbon, test substance, ethanol and water-soluble silicon


CONTROL AND BLANK SYSTEM

- Inoculum blank: Yes

- Abiotic sterile control: Yes

STATISTICAL METHODS: no statistical analysis was carried out.

Reference substance:

aniline

Remarks:

Reference value set to exceed 40% and 65%, respectively, of the degradation rate of aniline determined by BOD on day 7 and 14 respectively.

Key result

Parameter:

% degradation (O2 consumption)

Value:

5

Sampling time:

28 d

Key result

Parameter:

% degradation (test mat. analysis)

Value:

15

Sampling time:

28 d

Details on results:

Degradation calculated by BOD 4%, 6%, 6% - average 5%
Degradation obtained by HPLC 9%, 22%, 13% - average 15%
Degradation of reference on Day 7 and 14 determined by BOD was 57% and 77%, respectively.

Table 1. Analytical results.

 

		Water + TS	Sludge + TS			Theoretical value
Vessel		#6	#1	#2	#2
BOD	mg	0.0	2.2	3.7	3.7	58.2
DOC residual amount and rate	mgC	4.4	0.3	0.8	0.6	13.2
	%	33	3	6	4	-
Residual amount of test substance and residual rate (HPLC)	mg	22.2	27.4	23.5	26.0	30.0
	%	74	91	78	87	-
Production of ethanol and production rate (GC)	mg	5.0	0	0	0	17.3
	%	29	0	0	0	-
Production of water-soluble silicon and production rate (AA)	mg	0.6	0.4	0.7	0.6	3.6
	%	16	11	21	17	-
Mass balance of silicon portion	%	90	102	99	104	-

TS is test substance

Where vessel # is: 1, 2 and 3 – sludge + test substance; 4 – control blank; 5 – sludge + Aniline; 6 – water + test substance.

 

Table 2. Percentage of degradation on day 28.

 

	Degradation (%)
	#1	#2	#3	Average
Result by BOD	4	6	6	5
Result by HPLC	9	22	13	15

 

 

Table 3. Percentage BOD in the 28 day test.

 

	Sample days								Mean Deg. (%)
	7		14		21		28
Vessel #	BOD (mg)	Deg. (%)	BOD (mg)	Deg. (%)	BOD (mg)	Deg. (%)	BOD (mg)	Deg. (%)
5	52.3	57	71.7	77	72.1	77	72.2	76
4	0.7	-	1.8	-	2.2	-	3.6	-
1	1.5	1	3.1	2	4.3	4	5.8	4
2	2.0	2	3.7	3	5.6	6	7.3	6
3	2.2	3	3.9	4	5.5	6	7.3	6	5
6	0.0	-	0.0	-	0.0	-	0.0	-

Where vessel # is: 1, 2 and 3 – sludge + test substance; 4 – control blank; 5 – sludge + Aniline; 6 – water + test substance.

Deg is equal to percentage biodegradation.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

A biodegradation rate of 5% (O2 consumption) to 15% (test material analysis) in 28 days was determined for the substance in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Biodegradation in water: screening tests: 5% (O2 consumption) to 15% (test material analysis) degradation in 28 days (OECD 301C)

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

A biodegradation of 5% (O₂ consumption) to 15% (test material analysis) in 28 days was determined for the substance in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The result is considered to be reliable.

 

The constituents of the test substance hydrolyse within the timescale of the ready biodegradation study (half-life of 40 -130 h at pH 7) to their corresponding silanol hydrolysis products and ethanol. The biodegradation observed in the study is attributable to the biodegradation of the ethanol hydrolysis product.

 

Ethanol is readily biodegradable (OECD, 2004).

 

No significant biodegradation is expected for the silanol hydrolysis products.

 

The biodegradation rate found in the test is much lower than expected based on consideration of the chemical structure, based on hydrolysis to release ethanol (biodegradable ethanol/ethoxy groups accounting for nearly 60% of the parent structure by weight). The low solubility of the test substance may have resulted in the degradation rate being limited by dissolution into water.

 

Reference:

 

OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.