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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
other: read across from supporting substance
Adequacy of study:
weight of evidence
Study period:
From May 31 to June 28, 1995
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Deviations:
no
Principles of method if other than guideline:
Analysis conducted with internal method SAV: 13 000 03
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge of a communal sewage treatment plant Ara Reinach collected on 30.05.95
- Concentration of sludge: 530 mg/l
Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 150 mg/L
Based on:
DOC
Details on study design:
TEST CONDITIONS
- Test temperature: 20 - 25°C (room temperature)
- Continuous darkness: no, indirect daylight.
- Estimation Technique : TOC/DOC Analyzer 500TEST SYSTEM
- Number of culture flasks/concentration: 2 tests running in parallel
Reference substance:
diethylene glycol
Key result
Parameter:
% degradation (DOC removal)
Value:
ca. 1
Sampling time:
28 d
Details on results:
Adsorption: The adsorption of the test substance after 3 hours was 12 %.

The biodegradation of the reference substance, corrected by the blank control and measured as DOC (mg/l) is: 100 % 7th day (average of 2 tests running in parallel).

Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
The biodegradation of the test substance after 28 days was: 1 %
Executive summary:

The inherent biodegradability of test substance was determined in a Zahn-Wellens / EMPA test, performed according to the OECD Guideline for Testing of Chemicals, No. 302B, 1992. The test substance and the reference substance Diethylenglycol, respectively, were tested in concentrations of 150 mg/l DOC.

Results

Adsorption: The adsorption of the test substance after 3 hours was: 12 %

Biodegradation: The biodegradation of the test substance after 28 days was: 1 %

The total elimination of the test substance after 28 days was: 12 %

The biodegradation of the reference substance after 7 days was: 100 %

Endpoint:
biodegradation in water: screening test, other
Remarks:
BOD5/COD evaluation
Type of information:
other: read across from supporting substance
Adequacy of study:
weight of evidence
Study period:
September 23, 1975
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Qualifier:
according to
Guideline:
other: Internal method 15
Qualifier:
according to
Guideline:
other: Internal method 16
Principles of method if other than guideline:
The biological oxygen demand BOD is the amount of oxygen needed to degrade organic substances present in waste water with the help of bacteria (and other microorganisms present in sludge). The expression BOD5 represents the oxygen consumption within 5 days of incubation at 20 °C. Various dilutions of a substance solution in oxygen saturated water will be measured for its oxygen content before and after such an incubation period. Within this procedure chemical oxygen demand (COD) is defined as the equivalent amount of oxygen in terms of amount of potassium dichromate that is consumed by reacting with the oxidizable components of 1 g of sample material dissolved in 1 liter water under the given reaction conditions.
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
not specified
Duration of test (contact time):
ca. 21 d
Initial conc.:
ca. 500 mg/L
Based on:
test mat.
Initial conc.:
ca. 10 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks on result:
not determinable because of methodological limitations
Key result
Parameter:
BOD5
Value:
ca. 0 mg O2/g test mat.
Key result
Parameter:
COD
Value:
ca. 792 mg O2/g test mat.
Key result
Parameter:
BOD5*100/COD
Value:
ca. 0

Biochemical oxygen demand or BOD is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The term also refers to a chemical procedure for determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water, therefore is not be used as quantitative date about ready biodegradation.

Interpretation of results:
not readily biodegradable
Conclusions:
BOD5 = 0 mg/g O2
COD = 972 mg/g O2
BOD5/COD = 0
Executive summary:

The substance has been tested for biodegradation according to the Ciba Geigy AG internal method 15 and 16.

The substance shows the following results:

BOD5 = 0 mg/g O2

COD = 972 mg/g O2

BOD5/COD = 0

Description of key information

The substance is nor ready nor inherent biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The evaluation of biodegradation of the substance has been based on studies conducted on the Similar Substance 01. The complete hypothesis and justification for the read across approach has been attached in section 13

The substance has been tested by one screening study (BOD5, COD) and one study of inherently biodegradation.

The screening test has been conducted in 1975 according to the CIBA GEIGY AG internal method 15 and 16. The purity of substance is approx. 85 %.

COD/BOD5 ratio

Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) are the most commonly used parameters for the characterization of the biodegradability capacity.

COD results are typically higher than BOD5 values, and their ratio vary depending on the characteristics of the substrate. This ratio has been commonly used as an indicator for biodegradation capacity, the "Biodegradability index" (B.I.).

As indicated in the ECHA Guidance R.7b, the BOD5 test is a traditional biodegradation test that is now replaced by the ready biodegradability tests. Therefore, this test should not be performed today for assessment of the ready biodegradability of substances.

Older test data may, however, be used when no other degradability data are available.

For the assessment it is only available a summary on BOD5 and COD.

COD was measured according to Method A-16. The COD measured was 792 mg/g O2, at concentration of 500 mg/l.

BOD5 was measured according to Method A-15. The BOD5 measured was 0 mg/g O2, at concentration of 10 mg/l.

The ratio BOD5/COD is 0.

When the ratio BOD5/COD > 0.5 the situation can be compared with short time period degradation (readily biodegradable), but it is not our case.

No more data are available, therefore no other discussion can be made.

Inherent biodegradation

This evaluation is supported by the study of inherent biodegradation conducted according the guideline OECD 302B. The purity of substance is 90 %. After 28 days of test period, the biodegradation observed was 1 %.

Based on data in our possess, the substance is not ready biodegradable as shown on 5 days screening study and not inherently biodegradable on basis of the result of inherently biodegradation study after 28 days according to the OECD 302B.