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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
July-September 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: study acc. to GLP
Qualifier:
according to
Guideline:
EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)
Version / remarks:
in all essential parts identical with OECD Guideline 301 E
Principles of method if other than guideline:
The method assess the ready biodegradability of a test iteam under aerobic conditions at 22 +/- 2oC. Degradation is followed by DOC analysis at frequent intervals over a 28 day period. The degree of biodegradation is calculated by expressing the concentration of DOC removed (correccted for that in the blank inoculum control) as a percentage of the concentration initially present.
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
Test organism:
- type: mixed population of aquatic microorganisms
- origin: secendary effluent of a domestic sewage treatment plant
- pretreatment: separation of coarse particles by filtration
- concentration of effluents in reaction mixture: 0.5 ml/L
Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
The following type of flask were used:

- Test suspension (2 parallels)
A measured volume of mineral medium containing a known concentration of the test item (as the nominal sole source of organic carbon) and inoculum

- Procedure control (2 parallels)
In order to check the procedure, the reference chemical sodium benzoate is tested by setting up 2 flask in parallel to the normal tests runs.

- Inoculum blank (2 parallels)
A measured volume of mineral medium containing only inoculum

- Toxicity control (1 parallel)
Toxic effects of the test item are determined in a toxicity control flask (containing test item, reference substance and inoculum).

Each flask was inocuated with 0.5 ml effluent per litre medium. The mixtures were aerated in the dark at 22 +/- 2oC.

Degradation was followed by DOC analysis at frequent intervals over a 28 day period. The degree of biodegradation was calculated by expressing the concentration of DOC removed (correccted for that in the blank inoculum control) as a percentage of the concentration initially present.
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (DOC removal)
Value:
79
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
73
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
74
Sampling time:
21 d
Parameter:
% degradation (DOC removal)
Value:
84
Sampling time:
27 d
Parameter:
% degradation (DOC removal)
Value:
81
Sampling time:
28 d
Details on results:
All validity criteria of the test method were met:
- The reference compound has reached the level for ready biodegradability by 14 days
- no toxicity of the test item was observed in the toxicity control
- the difference of extremes of replicate values of the removal of test chemical at the end of the test is less than 20%.
- the DOC content of the blank control at the begining of the test is <= 5 mg/L.
Results with reference substance:
% degradation for reference substance:
- 7 days: 100%
- 14 days: 96%
- 21 days: 99%
- 27 days: 100%
- 28 days: 100%
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Within 28 days, a degradation of 81% was determined for Fe(III)IDHA. Fe(III)IDHA has to be classified as readily biodegradable.
Executive summary:

A study was performed to assess the ready biodegradablility of IDS Fe Komplex (Fe(III)IDHA).

The study was conducted in accordance with the Commission Directive 92/69/EEC. Method C.4 -B: Modified OECD Screening test. This test method is in all essential parts identical with OECD Guideline 301 E.

A solution of Fe(III)IDHA in a mineral medium was inoculated with secondary effluent from a domestic sewage treatment plant and incubated under aerobic conditions. Degradation was followed by DOC determinations at 0h, 7 d, 14 d, 21 d, 27 d and 28 d.

Fe(III)IDHA showed:

79% degradation after 7 days

73% degradation after 14 days

74% degradation after 21 days

84% degradation after 27 days

81% degradation after 28 days

Therefore Fe(III)IDHA has to be classified as "readily biodegradable".

The reference substance showed 96% degradation after 14 days.

Description of key information

Within 28 days, a degradation of 81% was determined for Fe(III)IDHA. Fe(III)IDHA has to be classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Biodegradability of Fe(III)IDHA was evaluated in two test:

- Method C.4 -B: Modified OECD Screening test. This test method is in all essential parts identical with OECD Guideline 301 E.

- OECD Guideline 302 B - Inherent Biodegradability. Method: Zahn-Wellens/EMPA-Test.

The both study showed good biodegradability of eveluated substance Fe(III)IDHA:

- 81% after 28 days in ready biodegradability study (OECD 301E)

- 92% after 28 days in inherent biodegradability test (OECD 302 B).