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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
7 June 2006 to 6 December 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study followed OECD Guideline 301 F

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report Date:
2006

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
GLP according to German "Chemikaliengesetz", EC and OECD Guideline principles

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sludge from the sewage plant in Hildesheim, Germany, comprising mostly municipal sewage (industrial chemical waste: 30-33%, referring to BOD)
- Pretreatment: The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was filled up with mineral salts medium and was maintained in an aerobic condition by aeration with CO2-free air for 4 days. 10 mL/L were used to initiate inoculation.
- Concentration of sludge: 10 ml/L
- Initial cell/biomass concentration: Colony forming units in the test vessels: 10E07-10E08 CFU/L
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
40 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F
- Test temperature: 19.5 - 22.0°C
- pH:
Start End
Inoculum Control 7.59 1) 7.56
2) 7.54
Functional Control 7.59 7.73
Test Item 1) 7.56 1) 7.51
2) 7.53 2) 7.53
Toxicity Control 7.50 7.72
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: brown glass bottles (volume 500 mL)
- Number of culture flasks/concentration: two replicates
- Measuring equipment: The oxygen consumption was determined continuously from the pressure in the incubation vessels by OxiTop(R) measuring system at 360 measuring points (every 112 minutes) during the 28 d incubation period.
- Test performed in closed vessels: closed with OxiTop(R) device (see above)

SAMPLING
The temperature in the incubator was documented continuously by a thermohygrograph.
At the beginning of the test the pH-values in the brown glass bottles (test item, toxicity control) and in the measuring flasks (inoculum control before dividing, functional control) were determined. At the end of the test the pH-values of the test solutions in the brown glass bottles were determined.

CONTROL AND BLANK SYSTEM
- Inoculum blank: mineral salts medium
- Toxicity control: test item and reference substance in test concentrations
- Functional control: benzoic acid, sodium salt
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Remarks on result:
other: 0% biodegradation after 7, 14, 21 and 28 d
Details on results:
Test item was tested in two replicates (see Table 1 below for detailed results)
pH at the end of all tests (test item, controls) was in the range of 6.0-8.5 (validity criterion), for detailed values, see above
Toxicity control showed 39% biodegradation after 14 d and 29% biodegradation after 28 d
Inoculum control showed oxygen depletion of 33.8 mg/l after 28 d

BOD5 / COD results

Results with reference substance:
Functional control (reference substance: 45 mg/l sodium benzoate) showed 94% biodegradation after 14 d and 92% biodegradation after 28 d

Any other information on results incl. tables

Table 1: Mean Biodegradation of the Test Item in Comparison to the Functional Control and Toxicity Control

 

Biodegradation [%]

 

[d]

 

Replicate

7

14

21

28

Test Item 40 mg/L

 

1

0

0

0

0

2

0

0

0

0

Functional Control 45 mg/L

1

82

94

90

92

Toxicity Control 40 + 45 mg/L

1

36

39

36

29

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
see above for details
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Not readily biodegradable in the 10-d window and after 28 days
Executive summary:

The ready biodegradability in the Manometric Respirometry Test was determined with a non adapted activated sludge for the test item over a period of 28 days. The study was conducted from 2006-06-20 to 2006-07-18 according to OECD guideline 301 F at DR.U.NOACK-LABORATORIEN, D-31157 Sarstedt. The test item concentration selected as appropriate was 40 mg/L, corresponding to a ThOD of 87.2 mgO2/L in the test vessel. The oxygen was depleted by the respiration of bacteria and the degradation was followed by measuring the oxygen concentration. The biodegradation is therefore expressed as the percentage BOD and was calculated for each study day.

The mean oxygen depletion in the inoculum control came to 33.8 mgO2/L after 28 days. In order to check the activity of the test system sodium benzoate was used as functional control. The pass level > 60 % was reached after 3 days. The biodegradation rate came to 92 % after 28 days.

In the toxicity control containing both test and reference item 39 % degradation occurred within 14 days. The degradation of the reference item was not inhibited by the test item.

The biodegradation of the test item is shown in Table 1 and graphically in Figure 1 in comparison to the readily degradable functional control. The 10 % level (beginning of biodegradation) was not reached until 28 days. The mean biodegradation remained at 0 %.

The validity criteria of the guideline are fulfilled.


The test item must be regarded as not readily biodegradable in the 10-d-window and after 28 days.