Registration Dossier

Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
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)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: • ISO Standard 10707, Water Quality - Evaluation in an aqueous medium of the "ultimate” aerobic biodegradability of organic compounds - Method by analysis of biochemical oxygen demand (closed bottle test) (1994).
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: The source of test organisms was secondary effluent freshly obtained from a municipal sewage treatment plant:
Details on inoculum:
Source:

The source of test organisms was secondary effluent freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Treatment:

Secondary effluent was filtered through a coarse filter paper, the first 200 ml was discarded. The filtrate was kept aerated until inoculation.

Inoculation:

4 ml filtrate of secondary effluent per litre of final volume.

Reason for selection:

The test has been accepted internationally (EC, OECD) for determining the 'ready' biodegradability of test substances under aerobic conditions.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Initial conc.:
5 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Mineral medium:

1 ml of solution (A) to (D) was mixed and made up to 1 litre with Milli-RO water.

Stock solutions of mineral components:

A) 8.50 g KH2PO4; 21.75 g K2HPO4; 67.20 g Na2HPO4.12H2O; 0.50 g NH4Cl:dissolved in 1 litre Milli-Q water, pH 7.4 + 0.2

B) 22.50 g MgSO4.7H2O dissolved in 1 litre Milli-Q water.

C) 36.40 g CaCl2.2H2O dissolved in 1 litre Milli-Q water.

D) 0.25 g FeCl3.6H2O dissolved in 1 litre Milli-Q water.

Test temperature: between 21.6 and 22.5°C.

pH: At start of the test from 7.5 to 7.6

pH adjustment: no

Continuous darkness: yes

TEST SYSTEM

Test bottles: 250-300 ml BOD bottles with glass stoppers.

Number of culture flasks/concentration: 2 flasks per measuring point

TEST SET UP:

Inoculum blank: Containing only inoculum (no test substance)

Procedure control: Containing reference substance and inoculum

Test suspension: Containing test substance and inoculum (applicable for both test concentrations)

Toxicity control: Containing test substance at the lowest concentration, reference substance and inoculum.

DETERMINATION OF OXYGEN CONCENTRATION:

Frequency: In duplicate; immediately at the start of the experiment (day 0), and at day 7, 14, 21 and 28.

Sampling method: Whole flask was used for measurement.

Measuring equipment: WTW inolab Oxi 730 supplied with a WTW CellOx 325 oxygen electrode, electrolyte type ELY/G.


Reference substance:
other: sodium acetate
Key result
Parameter:
% degradation (O2 consumption)
Value:
34 - 46
Sampling time:
28 d
Remarks on result:
other: at 2 mg/l
Key result
Parameter:
% degradation (O2 consumption)
Value:
45 - 48
Sampling time:
28 d
Remarks on result:
other: at 5 mg/l
Details on results:
The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed average biodegradation values of Amino Functional Alkoxysilanes between 34 and 46% at the lowest test concentration (2 mg/l) and between 45 and 48% at the highest test concentration (5 mg/l).

In the toxicity control more than 25% biodegradation occurred within 14 days (an average of 59%, based on ThOD). Thus, the toxicity control showed that Amino Functional Alkoxysilanes did not inhibit microbial activity
Results with reference substance:
The reference substance was degraded by at least 60% (average value: 76%) within 14 days
Validity criteria fulfilled:
yes
Interpretation of results:
other: Although substantial biodegradation was recorded after 28 days of incubation, Amino Functional Alkoxysilanes was not readily biodegradable under the conditions of the closed bottle test.
Conclusions:
34-46% biodegradation (2 mg/l) and 45-48% biodegradation (5 mg/l) in 28 days was attained 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: 34-46% (2 mg/L); 45-48% (5 mg/L) in 28 days (OECD 301D; O2 consumption)

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

34-46% biodegradation (2 mg/L) and 45-48% biodegradation (5 mg/L) in 28 days were attained in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The constituents of amino functional alkoxysilanes hydrolyse rapidly in water, to produce silanol hydrolysis products and methanol and ethanol.

To support the available data on the whole substance, measured constituents data are also taken into consideration where available. (3-Aminopropyl)triethoxysilane (CAS 919-30-2), attained 76% biodegradation in 28 days (M-lab 2005) in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (OECD 306, Biodegradability in seawater). REACH Guidance R7b states that: When a chemical attains >60% ThOD or >70% DOC removal in a Biodegradability in Seawater test (OECD 306), it can also be expected to fulfil the criteria for ready biodegradability. In a second study, a biodegradation of 67% in 28 days (not readily biodegradable) (Schoerberl 1994) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (EU Method C.4-A).

(3-Aminopropyl)triethoxysilane (CAS 919-30-2) hydrolyses within the timescale of the biodegradation study to 3-aminopropylsilanetriol and ethanol. The biodegradation observed in the studies are attributable to the biodegradation of the ethanol hydrolysis product.

Degradation of chemicals in seawater has generally been found to be slower than that in freshwater tests inoculated with activated sludge and sewage effluent [ECHA, 2008, Guidance on information requirements and chemical safety assessment, Chapter R.7b: Endpoint specific guidance]. Therefore, the screening test for biodegradability in seawater (Test Guideline 306) may be seen parallel to the ready biodegradability tests in freshwater [OECD, 2001 Series on testing and assessment Number 33]. In the present case the degradation of the substance did not reach the pass level of > 70% DOC removal within 28 days. Hence, the substance cannot be regarded as readily biodegradable.

Methanol and ethanol are readily biodegradable (OECD 2004a and OECD 2004b). The biodegradation observed in the studies is attributable to the biodegradation of the methanol and ethanol hydrolysis products.

No significant biodegradation is expected for the silanol hydrolysis products.

Reference:

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