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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2003-08-22 to 2003-09-24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP.
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated non-adapted sludge from the Marl-Ost municipal sewage treatment plant.

- Preparation of inoculum for exposure: inoculum batches were aerated with moist air for three days in the dark.

- Concentration of sludge: 20 ml sludge in 9980 ml mineral medium

- Initial cell/biomass concentration: 108 * 10(4) CFU/ml (colony forming units/ml)

- Water filtered: no
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS

- Composition of medium: See below

- Test temperature: 20.9 - 22.4

- pH: 7.1

- Aeration of dilution water: Aerated over night before addition of inoculum

- Suspended solids concentration: 7.4 mg/l

- Continuous darkness: yes

TEST SYSTEM

- Number of culture flasks/concentration: 2

- Measuring equipment: TOC-5000A; Shimadzu

SAMPLING

- Sampling frequency: days 0, 2, 7, 9, 14, 19, 21, 28

- Sampling method: TIC analysis

CONTROL AND BLANK SYSTEM

- Inoculum blank: Yes

- Abiotic sterile control: No

- Toxicity control: Yes

STATISTICAL METHODS: Not needed
Reference substance:
benzoic acid, sodium salt
Test performance:
Under the present test conditions, the test substance was biodegraded by an average of 86 % over the 28-day exposure period. The criterion for ready biodegradability (60 % within 10 days) was met.

The reference compound was biodegraded by an average of 93 % at the end of 28 days, confirming the suitability of the sludge inoculum.

Parameter:
% degradation (CO2 evolution)
Value:
86
Sampling time:
28 d
Remarks on result:
other: Batch of tested substance contains 50% methanol
Details on results:
See table 1
Results with reference substance:
See table 1

Table 1.  Percentage biodegradation of test item, of benzoic acid, sodium salt and of the toxicity control

Day

0

2

7

9

14

19

21

28

% Deg

D1

0.77

42.15

70.88

61.69

60.92

79.31

85.82

75.1

D2

0.38

36.4

88.12

90.8

93.87

62.84

82.67

97.7

mean

1

39

80

76

77

71

84

86

% Deg

R1

0

68.85

84.23

89.23

91.92

93.46

97.31

91.54

R2

0.77

69.23

91.15

86.15

90.77

96.54

95.38

94.23

mean

0

69

88

88

91

95

96

93

D1 – D2 = Dynasylan 2201

R1 – R2 = Benzoic acid, sodium salt

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
After 28 days, a mean degradation rate of 86 % was found in the study. However the tested batch of the substance, contains 50% methanol, which would biodegrade rapidly. Furthermore the substance hydrolyses in contact with water to a silanol hydrolysis product and ethanol. The silanol hydrolysis product, 3-Ureidopropylsilanetriol, is not expected to biodegrade to any significant extent. The high degradation rate is attributed to the rapid biodegradability of methanol and ethanol in the test media.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.
Reason / purpose:
read-across source
Parameter:
% degradation (CO2 evolution)
Value:
86
Sampling time:
28 d
Remarks on result:
other: Batch of tested substance contains 50% methanol

Description of key information

Not readily biodegradable(OECD 310) based on read across from CAS 23779 -32 -0. 

Key value for chemical safety assessment

Additional information

There are no reliable ready biodegradation data available for [3 -(trimethoxysilyl)propyl]urea (CAS 23843-64-3), therefore good quality data from the analogue substance, [3-(triethoxysilyl)propyl]urea (CAS 23779-32-0) have been read across. Both substances share the same silanol hydrolysis product (i.e. [3-(trihydroxysilyl)propyl]urea), the other hydrolysis products are methanol and ethanol, which are readily biodegradable (OECD, 2004a and OECD, 2004b). Details on read across justifications can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.  

The biodegradation of the analogue substance [3-(triethoxysilyl)propyl]urea (CAS 23779-32-0) was tested according to the OECD guidance 310 and GLP standards (2003). The inoculum - non adapted, activated sludge - was exposed for 28 d to 20 mg/L test substance. The tested batch of [3-(triethoxysilyl)propyl]urea, contains 50 % methanol, which would biodegrade rapidly. Furthermore [3-(triethoxysilyl)propyl]urea hydrolyses in contact with water to 3-Ureidopropylsilanetriol and ethanol. Ethanol is known to biodegrade rapidly as well. After 28 days, a mean degradation rate of 86% was found in the test. However the silanol hydrolysis product, 3-Ureidopropylsilanetriol, is not expected to biodegrade to any significant extent. The high degradation rate is attributed to the readily biodegradability of methanol and ethanol in the test media. The biodegradation of the silanol hydrolysis product, once a complete biodegradation of methanol and ethanol has been taken into account can thus be regarded as negligible.

On this basis the substance [3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3) is not considered as readily biodegradable.