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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: inherent biodegradability
Remarks:
Inherent Biodegradability: Modified MITI Test
Type of information:
experimental study
Adequacy of study:
key study
Study period:
January 25, 2000 to February 23, 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
In general, by the nature of their design and use, disperse dyes are not intended to be readily biodegradable as this would assist in the rapid destruction of the dyestuff, rendering it unfit for purpose. As such, it is accepted that such substances are not readily biodegradable under relevant environmental conditions. A published study (Pagga & Brown, 1986) describes the results of the testing of 87 dyestuffs in short-term aerobic biodegradation tests. The authors of this publication concluded that dyestuffs are very unlikely to show any significant biodegradation in such tests and that there seems little point in carrying out such test procedures on dyestuffs. Therefore, an inherent degradation test was performed only.
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Deviations:
yes
Remarks:
The test substance was run in duplicate instead of in triplicate.
GLP compliance:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 99 Labormischung 1
- Expiration date of the lot/batch: 01/2005

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Solubility of the test substance in the solvent/vehicle: insoluble
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: Mixture of polyvalent bacteria (activated sludge) collected on January 25, 2000 from the aeration tank of a domestic sewage treatment plant, PRO RHENO Basel communal.
- pH value of the activated sludge: 6.6
- Pretreatment: The activated sludge was washed 4 times with tap water and one time with test medium. Subsequently, the sludge was aerated until use. A sample of the activated sludge was taken to determine the dry weight of the suspended solids.
- Concentration of sludge: 100 mg/l suspended solids. The bacteria concentration was obtained by adding 10.4 ml of the pre-treated sludge (9.6 g/l SS) per 1000 ml test medium.
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
This method was based on the following conditions:
• Test chemicals as sole organic carbon sources
• No pre-adaptation of micro-organisms to the test chemicals
For each test series the following number of test flasks was set up:
• Test substance 2 flasks with inoculum + test medium + test substance
• Inoculum control 1 flask with inoculum + test medium
• Procedure control 2 flasks with inoculum + test medium + reference compound
• Abiotic control 1 flask with distilled water + test substance
Reference substance:
other: Sodium benzoate
Test performance:
This method was based on the following conditions:
• test chemicals as sole organic carbon sources
• no pre-adaptation of micro-organisms to the test chemicals
For each test series the following number of test flasks was set up:
• Test substance 2 flasks with inoculum + test medium + test substance
• Inoculum control 1 flask with inoculum + test medium
• Procedure control 2 flasks with inoculum + test medium + reference compound
• Abiotic control 1 flask with distilled water + test substance
The test was performed in a Voith Sapromat apparatus.
The chemicals tested were inoculated in the testing vessels with micro-organisms. During the test period, the Biochemical Oxygen Demand was measured continuously by means of a BOD-meter. The biodegradation was calculated on the basis of the theoretical oxygen demand (ThOD).
The oxygen consumption was automatically measured by the test apparatus (Voith Sapromat). The selected measuring range was x1,(250 ml test medium per flask). The oxygen consumption was given in milligrams O2 per litre.
The pH value of all incubation flasks was measured at the beginning and at the end of the test.
Key result
Parameter:
% degradation (O2 consumption)
Value:
13
Sampling time:
28 d
Details on results:
Biodegradation of FAT 93503/A:
after 7 days 10 %
after 14 days 13 %
after 28 days 13 %

BOD5 after 5 days is 100 mg/O2/g

In the abiotic control the degradation after 28 days was 0 %.
Parameter:
BOD5
Value:
100 mg O2/g test mat.
Results with reference substance:
Biodegradation of the reference substance:
The concentration of the test substance was 100 mg/l.
- Biodegradation after 7 days 74 %
- Biodegradation after 14 days 88 %
- Biodegradation after 28 days 100 %
Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
FAT 93503/A is not inherently biodegradable.
Executive summary:

A study was carried out to determine if FAT 93503/A is inherently biodegradable. This study was perfomed according to the OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II)). The test system used for the experiment is a mixture of polyvalent bacteria (activated sludge obtained from a communal wastewater treatment). The duration of the test was 28 days. The experiment was done in a static condition, at 25 °C, continuously stirred and in the dark. The test volume was 250 ml and the test concentration of FAT 93503/A was 30 mg/l. The reference substance (Sodium benzoate), was used at 100 mg/l. The biodegradation of the reference substance after 7, 14 and 28 days was 74 %, 88 % and 100 %, respectively while the biodegradation of FAT 93503/A after 7, 14 and 28 days was 10 %, 13 % and 13 %, respectively. In conclusion, FAT 93503/A is not inherently biodegradable (Biodegradation is <20 %). The BOD5 after 5 days is 100 mg O2/g.

Description of key information

A study was carried out to determine if FAT 93503/A is inherently biodegradable. This study was perfomed according to the OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II)). The test system used for the experiment is a mixture of polyvalent bacteria (activated sludge obtained from a communal waste water treatment). The duration of the test was 28 days. The experiment was done in a static condition, at 25 °C, continuously stirred and in the dark. The test volume was 250 ml and the test concentration of FAT 93503/A was 30 mg/l. The reference substance (Sodium benzoate), was used at 100 mg/l. The biodegradation of the reference substance after 7, 14 and 28 days was 74 %, 88 % and 100 %, respectively, while the biodegradation of FAT 93503/A after 7, 14 and 28 days was 10 %, 13 % and 13 %, respectively. In conclusion, FAT 93503/A is not inherently biodegradable (Biodegradation is <20 %). The BOD5 after 5 days is 100 mg O2/g.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information