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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998-02-19 to 1998-06-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study conducted in compliance with OECD Guideline 301F without any deviation.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Name of test material (as cited in study report): DIMETOL
- Substance type: colourless to pale yellow liquid
- Analytical purity: 99.4%
- Lot/batch No.: 281961

PHYSICO-CHEMICAL PROPERTIES
density: 0.815 g/ml at 20°C
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage in the city of Geneva
- Storage conditions/Preparation of inoculum for exposure: washed tree times in the mineral medium and kept aerobic being used in the same day
- Concentration of sludge: 2.260 g/L (dry weight of suspended solids); to obtain a concentration of 30 mg/L (dry weight) in a 250 mL flask, 3.32 mL of sludge is needed (inoculum).
Duration of test (contact time):
34 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: compliant with recommendations of TG on mineral medium
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: 22°C
- pH: 7.30 (initial) to a mean of 7.68 (final) from 7.22 to 8.23.
- pH adjusted: no
- Suspended solids concentration: 30 mg/l
- Continuous darkness: not stated

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: stirring
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: SAPROMAT D12
- Test performed in closed vessels due to significant volatility of test substance: yes
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: soda lime pellets

SAMPLING
- Sampling frequency: everyday O2 consumption is recorded and correct temperature and stirring are checked
- Sampling method: SAPROMAT automatic measurement

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes

Reference substance:
benzoic acid, sodium salt
Remarks:
Purity 99.0 %
Key result
Parameter:
% degradation (O2 consumption)
Value:
75
Sampling time:
28 d
Details on results:
- Initial test material concentration: 100 mg/L (nominal)
- Theoretical oxygen demand (ThOD) = 2.99 mg O2/mg
- % biodegradation on Day 34 = 76%

Biodegradation starts on day 6 and reaches 66% at the end of the 10-day window (day 6 to 16).
Results with reference substance:
Degradation of the reference substance exceeds 40% after 7 days and 65% after 14 days. The test is the considered as valid.

Table 1 Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations)

 

Days

6

7

16

21

28

34

BOD sludge

1stflask

B1

18.0

18.0

22.0

26.0

28.0

28.0

2ndflask

B2

14.0

14.0

18.0

20.0

23.0

25.0

Mean

B

16.0

16.0

20.0

23.0

25.5

26.5

BOD Test Subst.

1stflask

C1

56.0

95.9

219.8

236.5

249.2

256.0

2ndflask

C2

53.7

87.6

215.4

237.8

247.5

252.4

1stfl. Corr.

C1-B

40.0

79.9

199.8

213.5

223.7

229.5

2ndfl. Corr.

C2-B

37.7

71.6

195.4

214.8

222.0

225.9

% degr.

1stflask

D1

13

27

67

71

75

77

2ndflask

D2

13

24

65

72

74

76

mean

D

13

25

66

72

75

76

B=(B1 +B2)/2

D1=100*(C1 -B) / ThOD * S

D2=100*(C2 -B) / ThOD * S

D=(D1 +D2) / 2

[S] : initial test substance concentration (mg/l)

ThOD = 2.99 mg O2 / mg

MW = 144.26 g/mol

formula = C9H20N0O1

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Under the test conditions, the substance is considered as readily biodegradable. The substance achieved > 60% after 28 days and passed the 10-day window criterion
Executive summary:

The biodegradation of Dimetol was studied using a Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 301F. Inoculum came from fresh activated sludge from a biological waste water treatment plant in Geneva that treated predominantly domestic sewage. Sodium Benzoate was used as a reference substance. Toxicity of the test substance has been investigated and showed no inhibition. Initial concentration of the test substance was 100 mg/l. Biodegradation of the test substance is recorded by the evolution of the O2 consumption during the study. O2 consumption was recorded every day.

Dimetol undergoes 75% biodegradation after 28 days. Biodegradation starts on day 6 and reaches 66% at the end of the 10 -day window. Therefore, and in accordance with The OECD Guidelines 301F, Dimetol is considered as ready biodegradable. Validity criteria are all met, the study is considered as acceptable for the endpoint.

Description of key information

The ready biodegradability of Dimetol was determined by the Manometric Respiratory Test according to OECD Guidelines No 301F. Under the conditions of the study the test substance underwent 75 % biodegradation after 28 days. Biodegradation started on day 6 and reached 66 % at the end of the 10-day window (days 6 to 16). Thus, the test substance should be regarded as readily biodegradable according to this test.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information