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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:
2000-11-16 to 2000-12-14
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
(1992)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
(1992)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source: STP Gross-Zimmern (Germany)
- Preparation of inoculum: Centrifugation, decantation and resuspension in tap water (repeated twice); preparation of 4 g dry weight/l in test water; aeration until use; filtration through cotton wool before use.
Duration of test (contact time):
<= 28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Initial conc.:
2.1 mg/L
Based on:
test mat.
Remarks:
toxicty control
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
- Culturing apparatus: 250 ml Karlsruher flasks, filled completely and closed with glass stoppers
- Number of culture flasks per concentration: 8 x 2 with test substance (10.0 mg/5 l = 2.00 mg/l) and inoculum 8 x 2 with reference substance (2.06 mg/l) and inoculum (procedure control) 8 x 2 with inoculum only (inoculum control) 5 x 2 with test (2.10 mg/l) and reference (2.06 mg/l) substances and inoculum (toxicity control)
- Test temperature: 22 °C
- pH value: 7.6 (start)
- Intense stirring of 10.0 mg test substance in 5 l water for 15 minutes, addition of 2.5 ml filtered inoculum
- Composition of medium: (A) Dissolved deionized water, total volume 1000 ml: 8.50 g KH2PO4 21.75 g K2HPO4 33.40 g Na2HPO4 * 2 H2O 0.50 g NH4Cl (B) Dissolved deionized water, total volume 1000 ml: 22.50 g MgSO4 * 7 H2O (C) Dissolved deionized water, total volume 1000 ml: 36.40 g CaCl2 * 2 H2O (D) Dissolved deionized water, total volume 1000 ml: 0.25 g FeCl3 * 6 H2O 1 drop of concentrated HCl 1 ml each of (A) + (B) + (C) + (D) in deionized water, total volume 1000 ml. 20 minutes aeration + 20 hours standing at test temperature leads to 8.7-8.8 mg O2/l at the start of the test
- Concentration of suspended solids: 4000 mg/l x 2.5 ml/5000 ml = 2 mg/l
- Measuring equipment: Oxygen electrode (WTW Oxi 340, Wissenschaftliche Technische Werkstätten GmbH, Weilheim, Germany)
- Oxygen measurements on days 0, 1, 5, 7, 12, 14, 21, and 28 (toxicity control only on days 0, 7, 14, 21, 28)
- Other relevant factors: darkness

Reference substance:
aniline
Key result
Parameter:
% degradation (O2 consumption)
Value:
1
Sampling time:
28 d
Details on results:
- Toxicity control (i2.1 mg/L test substance)
42 % degradation (14 days)
57 % degradation (28 days)
Conclusion: The test substance did not inhibit the microorganisms.
- Inoculum control
Oxygen depletion 0.7 mg/l, i.e. not above 1.5 mg/l

Results with reference substance:
Kinetic of control substance (in %):
= 62 after 7 day(s)
= 95 after 28 day(s)
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance is not considered to be readily biodegradable.
Executive summary:

The test substance was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days according to OECD 301 D. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. Under the test conditions, the percentage biodegradation of the test substance was 1 % after 28 days. Hence, the test substance is not considered to be readily biodegradable.

Description of key information

The test substance was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days according to OECD 301 D. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. Under the test conditions, the percentage biodegradation of the test substance was 1 % after 28 days. Hence, the test substance is not considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information