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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
01.02.2007 to 04.05.2007
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report

Materials and methods

Test guideline
according to guideline
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Test material form:

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
The study was performed with aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, FOllinsdorf, Switzerland) treating predominantly domestic wastewater. The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.

Based on this ratio, calculated amounts of wet sludge were suspended in test water (see Section 2.4.1) to obtain a concentration equivalent to 4 g (±10%) dry material per liter. During the holding period of four days prior to use, the sludge was aerated at room temperature. Prior to use, the sludge was first thoroughly mixed and then diluted with test water to a oncentration of 1 g per liter (dry weight basis). Based on the determined dry weight of this diluted activated sludge, defined amounts were added to test water to obtain a final concentration of 100 mg dry material per liter.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
287 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Key result
% degradation (O2 consumption)
Sampling time:
28 d

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
not inherently biodegradable
Biodegradation after 28 days= 0%
Executive summary:

The test item Fluowet I 600 was investigated for its inherent biodegradability in a manometric respirometry test over 28 days, based on the OECD Guideline for Testing of Chemicals No. 302 C (1981). The following modifications were made: activated sludge from one source was used, the activated sludge was not fed during the holding period of maximum seven days, the test was run at 22 °C, the test water composition was slightly changed, and only the biological oxygen demand (BOD) was monitored, no test item specific analysis was performed. The biochemical oxygen demand (BOD) of the test item Fluowet I 600 in the test media was in the normal range found for the inoculum controls. Consequently, Fluowet I 600 was not biodegradable under the test conditions within 28 days.

In the toxicity control, containing both Fluowet I 600 and the reference item sodium benzoate, no inhibitory effect on the biodegradation of the reference item was determined. Thus, Fluowet I 600 had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 288 mg/L.

In the procedure controls, the reference item (sodium benzoate) was degraded by an average of 77% and 84% by Exposure Days 7 and 14, respectively; thus confirming suitability of the activated sludge. By the end of the test (Exposure Day 28), the reference

item was degraded by an average of 87%.