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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:
1996-10-15 to 1996-11-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 301F with GLP compliance. All validity criteria were fulfilled and no deviations were observed.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Remarks:
Statement of compliance with GLP in date of 1996-11-29
Specific details on test material used for the study:
No additional information
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day,
Concentration of sludge: 2.982 g/L (dry weight of suspended solids); to obtain a concentration of 30 mg/L (dry weight) in a 250 mL flask, 2.52 mL of sludge is needed (inoculum).
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: compliant with recommendations of TG on mineral medium
The pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Solubilising agent (type and concentration if used): None
- Test temperature: 22 °C
- CEC (meq/100 g): No data
- Aeration of dilution water: No data
- Suspended solids concentration: 30 mg/L
- Continuous darkness: No data
- Water: The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

TEST SYSTEM
- Culturing apparatus: Test flasks of the SAPROMAT
- Number of culture flasks/concentration: 2
- Measuring equipment: The respirometer used during this study is a SAPROMAT D 12, made by J. M. VOITH GmbH, D-7920 Heidenheim.
- Test performed in closed vessels: Yes
- Test performed in open system: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Procedure control: Yes with the reference substance
- Toxicity control: Yes
Reference substance:
aniline
Preliminary study:
None
Test performance:
Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked. At the end of the test period (normally 28 days), the pH of each flask is measured again.
Key result
Parameter:
% degradation (O2 consumption)
Value:
79
Sampling time:
28 d
Details on results:
Test substance undergoes 79 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 2 and reaches 79 % at the end of the 10-day window (days 2 to 12).
Test substance at 100 mg/L is not inhibitory to the micro-organisms.
Results with reference substance:
Degradation of aniline exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum was thus verified (validity criterion).

Table 5.2.1/2: Test substance - Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations)

 

Days:

2

7

12

14

21

28

BOD sludge

1st flask

B1

6.0

15.0

19.0

21.0

26.0

32.0

2nd flask

B2

7.0

17.0

20.0

23.0

29.0

35.0

mean

B

6.5

16.0

19.5

22.0

27.5

33.5

BOD test substance

1st flask

C1

48.7

181.3

204.0

208.0

215.9

219.8

2nd flask

C2

52.5

185.2

206.0

209.8

214.5

217.4

1st flask corr.

C1-B

42.2

165.3

184.5

186.0

188.4

186.3

2nd flask corr.

C2-B

46.0

169.2

186.5

187.8

187.0

183.9

% biodegradation

 

1st flask

D1

18

71

79

79

80

80

2nd flask

D2

20

72

80

80

80

79

mean

D

19

71

79

80

80

79

 

Calculations:

B = (B1 + B2) / 2

DI = 100 * (C1 - B) / ThOD * [S]

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

D = (DI + D2)/2

[S] : Initial test substance concentration (mg/L)

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item undergoes 79 % biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled. Thus, the test item should be regarded as readily biodegradable according to this test. In addition, no toxic effects of the test substance were observed to microorganisms at the test concentration.
Executive summary:

The ready biodegradability of the test item has been determined by the Manometric Respirometry Test according to the OECD Guideline No. 301F with GLP compliance.

A nominal concentration of test substance (100 mg/L)was introduced into the system.

The test substance was not found to be inhibitory to the micro-organisms at a concentration of 100 mg/L. The test item undergoes 79 % biodegradation after 28 days under the test conditions. Biodegradation started on day 2 and reached 79 % at the end of the 10 -day window (days 2 to 12). Degradation of aniline exceeded 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified as acceptable.

 

According to this test, the conclusion is that the test item should be regarded as readily biodegradable.

Description of key information

OECD Guideline 301F, GLP, key study, validity 1:

79% biodegradation after 28 days within the 10-day window.

Readily biodegradable. 

Non-toxic to microorganisms up to 100 mg/L.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One valid key study is available (Givaudan, 1996), to assess the readily biodegradation of the registered substance.

This study was performed on the registered substance according to OECD Guideline 301F and GLP. The test substance at 100 mg/L was inoculated with activated sludge from a biological wastewater treatment plant treating predomantly domestic sewage. The degradation of the test substance was assessed by the determination of the oxygen consumption. The test substance was biodegraded by 79% after 28 -day exposure period. Biodegradation started on day 2 and reached 79% at the end of the 10 day window (days 2 to 12). Therefore, the test substance is considered readily biodegradable. In the toxicity control, containing both the test substance and the reference substance (aniline), the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L. In the procedure controls, the degradation of the reference substance exceeded 40% after 7 days and 65% after 14 days, thus confirming suitability of the activated sludge.