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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:
November 1992
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
mixture of sewage, soil and natural water
Duration of test (contact time):
28 d
Initial conc.:
1 980 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: test substance, water, (different) mineral nutrients stock solution and oxygen saturated water
- Additional substrates (for the mineral nutrients stock solutions): KH2P04, K2HPO4, Na2HP04 ·2 H20, NH4CI, MgS04 · 7 H20, CaCl2, FeCl3 · 6 H20
- Test temperature: 20 °C
- Aeration of dilution water: yes

TEST SYSTEM
- Culturing apparatus: 300 mL BOD bottle
- Number of culture flasks: 8
- Method used to create aerobic conditions: Closed Bottle Test
- Measuring equipment: Oxygen electrode

SAMPLING
- Sampling frequency: Examination of the O2 consumption after day 5, 15 and 28 by oxygen electrode

CONTROL AND BLANK SYSTEM
- Inoculum blank: activated sludge, standard soil, water
Key result
Parameter:
% degradation (O2 consumption)
Value:
105
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
93
Sampling time:
15 d
Parameter:
% degradation (O2 consumption)
Value:
83
Sampling time:
5 d
Interpretation of results:
readily biodegradable
Conclusions:
After 5 days more than 80% and after 28 days the complete test substance was degraded. The test substance can be considered as readily biodegradable.
Executive summary:

The biodegradation of the test substance was determined in accordance to the OECD Guidline 301 D (Closed Bottle Test). The mineral nutrients stock solution was prepared after the requirements of the Guidline; the inoculum was made from equal proportions of outlet and backflow of an activated sludge STP as well as a suspension of standard soil. The consumption of the oxygen was determined after 5, 15 and 28 days by the use of an oxygen electrode. Next to this control- and blank test were implemented as well as the examination of the efficiency of the inoculum: 118% of the reference substance was degraded under the test conditions. The theoretical oxygen demand was calculated as 2.27 mg O2/mg test substance.

The test substance showed the following biodegradability:

 time [days]  BOD [%]
 5 83 
 15 93 
 28 105 

The test substance can be considered as readily biodegradable.

Description of key information

The test for the determination of biodegradation in water (OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)) showed, that after 5 days more than 80% and after 28 days the complete test substance was degraded. Based on this result, the test substance can be considered as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information