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EC number: 201-083-8 | CAS number: 78-10-4
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
- Endpoint:
- biodegradation in water: ready biodegradability
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- From 1992-10-27 to 1993-11-24
- 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)
- Deviations:
- no
- GLP compliance:
- yes
- Oxygen conditions:
- aerobic
- Inoculum or test system:
- activated sludge, domestic (adaptation not specified)
- Details on inoculum:
- - Source of inoculum/activated sludge: Living slime from a primarily communal sewage treatment plant (Marl - East). Collected 10/27/92.
- Preparation of inoculum for exposure: Washed, re-suspended in mineral medium
- Initial cell/biomass concentration: 5.17 g dry weight per litre - Duration of test (contact time):
- 28 d
- Initial conc.:
- 9.6 mg/L
- Based on:
- DOC
- Initial conc.:
- 1 000 mg/L
- Based on:
- test mat.
- Parameter followed for biodegradation estimation:
- DOC removal
- Details on study design:
- TEST CONDITIONS
- Test temperature: 21.8 - 22.1°C
- Suspended solids concentration: 25.9 g/ml
- Continuous darkness: yes
TEST SYSTEM
- Culturing apparatus: 2000 ml Erlenmeyer flasks with loose closure of aluminium foil.
- Number of culture flasks/concentration: Two test substance (9.6 mg DOC/l); Two control (9.71 mg DOC/l)
SAMPLING
- Sampling frequency: 0, 7, 14, 21, 27 and 28 d.
CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes - Reference substance:
- benzoic acid, sodium salt
- Key result
- Parameter:
- % degradation (DOC removal)
- Value:
- 98
- Sampling time:
- 28 d
- Details on results:
- The degree of biodegradation exceeded 70% within a 10 day window.
The positive control substance, sodium benzoate, achieved a biodegradation rate of 99% within 28 days. - Validity criteria fulfilled:
- yes
- Interpretation of results:
- readily biodegradable
- Conclusions:
- A biodegradation rate of 98% was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The substance may be considered readily biodegradable.
Reference
Table 1: Dissolved organic carbon levels (mg/l) and calculated % DOC reduction
Type of suspension |
0 |
7 |
14 |
21 |
27 |
28 |
||||||
DOC (mg/l) |
DOC reduction (%) |
DOC (mg/l) |
DOC reduction (%) |
DOC (mg/l) |
DOC reduction (%) |
DOC (mg/l) |
DOC reduction (%) |
DOC (mg/l) |
DOC reduction (%) |
DOC (mg/l) |
DOC reduction (%) |
|
|
|
|
|
|
|
|
|
|
|
|||
Test sample Replicate 1 |
10.32 |
0 |
1.37 |
94 |
0.80 |
98 |
0.76 |
96 |
0.82 |
98 |
0.72 |
98 |
Test sample Replicate 2 |
9.85 |
0 |
1.40 |
93 |
0.66 |
99 |
0.84 |
95 |
0.77 |
98 |
0.68 |
98 |
Median value |
0 |
93 |
|
98 |
|
96 |
|
98 |
|
98 |
||
|
|
|
|
|
|
|
|
|
|
|
||
Blank Replicate 1 |
0.53 |
|
0.76 |
|
0.57 |
|
0.41 |
|
0.62 |
|
0.50 |
|
|
|
|
|
|
|
|
|
|
|
|||
Reference substance Replicate 1 |
10.06 |
0 |
0.91 |
98 |
0.75 |
98 |
0.95 |
94 |
0.73 |
99 |
0.64 |
98 |
Reference substance Replicate 2 |
10.42 |
0 |
0.86 |
99 |
0.52 |
101 |
0.86 |
95 |
0.68 |
99 |
0.61 |
99 |
Description of key information
Biodegradation in water: screening tests: 98% degradation (DOC removal) in 28 days (EU C.4-A); biodegradation is not relevant for silicic acid being inorganic. Ethanol is readily biodegradable.
Key value for chemical safety assessment
- Biodegradation in water:
- readily biodegradable
- Type of water:
- freshwater
Additional information
A biodegradation of 98% in 28 days (DOC removal) was determined for the submission substance in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (EU C.4-A) (Evonik 1993).
Tetraethyl orthosilicate (CAS 78-10-4; EC No. 201-083-8) hydrolyses rapidly (t1/2 = 4.4 h at pH 7 and 25°C) in contact with water to form monosilicic acid (CAS 10193-36-9; EC No. 233-477-0) and ethanol (CAS 64-17-5; EC No. 200-578-6).
The biodegradation observed in the study is attributable to the biodegradation of the ethanol hydrolysis product which is readily biodegradable.
Biodegradation is not relevant for silicic acid as it is inorganic. Monosilicic acid exists only in dilute aqueous solutions and readily condenses at concentrations above approximately 100-150 mg/L as SiO2 to give a dynamic equilibrium between monomer, oligomers and insoluble polysilicic acid. These are naturally-occurring inorganic substances and degradation studies are not relevant. The silanol hydrolysis products will enter the natural biogeochemical cycle for silicon.
Ethanol is readily biodegradable (OECD 2004).
Reference:
OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.
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