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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: screening test, other
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30 March 1995 - 19 June 1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1995
Report date:
1995

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Version / remarks:
May 1981
Qualifier:
according to guideline
Guideline:
EU Method C.4-F (Determination of the "Ready" Biodegradability - MITI Test)
Version / remarks:
1992
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
The inoculum was derived from ten different sites in Switzerland, including activated sludge from domestic and industrial sewage (seven sites) and surface water from three different rivers.

One liter of the various samples was collected and immediately aerated. After transportation, it was centrifuged and washed two times in mineral medium. Thereafter, the sludge was resuspended in mineral medium at a concentration of 3 to 5 g of dry sludge per liter. Finally, the suspension was stirred and aerated for 24 hrs prior to use.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
ca. 30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
An automated closed system oxygen consumption measuring apparatus (VOITH SAPROMAT®) was used. The machine has a control and display unit. Substances to be tested were inoculated in the testing vessels under aerobic conditions with microorganisms (activated sludge). The reaction processes consume the dissolved oxygen and generate CO2. Granular sodium lime, grain size 2-5 mm (Fluka, No. 72073), is used for CO2 adsorption. The sodium lime contains a color indicator to indicate a saturation with CO2. The resulting decrease in pressure is detected and converted into an electrical signal by means of an electrode type manometer. The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulfate solution. Biodegradation is calculated by dividing the consumed oxygen by the theoretical oxygen demand of the substance. A control experiment using aniline as a reference substance was run in parallel. Furthermore, an inhibition test was included, where the test substance was incubated in the presence of the reference substance to determine a possible toxic effect of the test substance on activated sludge microorganisms.
Reference substance
Reference substance:
aniline

Results and discussion

Preliminary study:
none
Test performance:
The test substance was poorly water soluble and was therefore added directly into the test vessels.
Temperature (water bath): 25 °C
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
Theoretical oxygen demand (ThOD) of test substance: 2.23 mg O2/mg substance

BOD5 / COD results

Results with reference substance:
The biodegradation of the reference substance anilin was 70% after 7 days and 108% at the end of the test. The plateau was reached after 18 days.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The used inherent biodegradability test shows no evidence for biodegradation of menadione after 28 days of incubation with activated sludge. Furthermore, it is slightly toxic to microorganisms of activated sludge.
Executive summary:

The theoretical oxygen demand for the reference substance is 2.41 mg O2/mg substance (corresponds to 241 mg O2

for 100 mg substance). The respective oxygen demand for the test substance is 2.23 mg O2/mg substance. This corresponds to 66.9 mg O2 for 30 mg test substance. These ThOD values were used to calculate the % degradation.

The biodegradation of the reference substance aniline was 70 % after 7 days and 108 % at the end of the test. The plateau was reached after 18 days.

The test substance showed no degradation after 28 days of testing. The negative values indicate, that respiration of the microorganisms in the presence of Menadione is considerably reduced compared to conditions without test compound.

When the reference substance was incubated in the presence of the test substance, degradation of the reference substance was slightly inhibited. The degradation of the reference substance under these conditions was 87 % at the end of the test.

As an inference, the used inherent biodegradability test shows no evidence for biodegradation of menadione after 28 days of incubation with activated sludge. Furthermore, it is slightly toxic to microorganisms of activated sludge.