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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:
1988
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions: Only measurements from two replicates.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: ISO 10708: Water quality - Evaluation in an aqueous medium of the ultimate aerobic biodegradability of organic compounds - Determination of biochemical oxygen demand in a two-phase closed bottle test
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: Sewage treatment plant Hochdahl, predominantly municipal sewage, serving for a population equivalent of approx. 27000
- Concentration of sludge: 2.5 - 3.5 mg/L test medium
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
100 mg/L
Based on:
other: ThOD
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Deionised water was used for preparation of test medium. Mineral medium (according to OECD 301) was inoculated with activated sludge and after addition of a magnetic stirrer stabilised under laboratory conditions for approximately one week
- Test temperature: 20-25 °C
- Suspended solids concentration: 2.5-3.5 mg activated sludge/L test medium
- Other: The test substance was weighed on a piece of glass to an amount of about 20 mg ThOD and directly put into the test flask. The homogeneous distribution of the test substance was supported by continuous shaking of the test flasks during the whole incubation period.

TEST SYSTEM
- Culturing apparatus: 300 mL bottles, containing 200 mL test medium
- Number of culture flasks/concentration: three replicates prepared but results only from two results
- Method used to create aerobic conditions: the bottles were aerated with compressed air until O2 saturation was reached
- Measuring equipment: O2 determinations were performed using a O2-electrode (WTW; FRG; micorprocessor oximeter OXI 2000 with electrode model TriOxmatic EO 200)

SAMPLING
- Sampling frequency: after 7, 14, 21, 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 3
- Reference control: yes, 3
Reference substance
Reference substance:
acetic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (O2 consumption)
Value:
64
Sampling time:
28 d
Details on results:
The test substance is degraded in excess of 60% after 28 day test duration. However despite being biodegraded in excess of 60% after 28 days (64%), the test did not meet the "14-day window" criteria. Nevertheless, as the substance is an UVCB substance and thus consist of constituents with different degrees of esterification, sequential (instead of concurrent) biodegradation is expected to take place. Thus, referring to Annex I to the OECD Guideline for Testing of Chemicals ‘Revised introduction to the OECD guidelines for testing of chemicals, section 3’ (OECD, March 2006), the 10-day window criterion can be disregarded in this case and the substance considered as readily biodegradable.

BOD5 / COD results

Results with reference substance:
82% of the reference substance sodium acetate was biodegraded after 7 days and 92% after 14 days, thus the validity criterion are fulfilled.

Any other information on results incl. tables

One replicate containing test substance was not measured. The oxygen uptake in the blank bottles after the first week of the test is lower than 3 mg O2 and in the following weeks lower than 1 mg O2 per week (validity criteria fulfilled)

Table 1: Results with test substance

% oxidation

Incubation time [d]

7

14

21

28

Replicate 1

-

-

-

-

Replicate 2

2

29

56

65

Replicate 3

5

28

52

63

Mean (b+c)

3

28

54

64

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable