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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From June 22, 1999 to July 20, 1999
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to EU Method C.4-B, in compliance with GLP.

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
according to
EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)
GLP compliance:

Test material

Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report): Reaktiv Orange F97 0318

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Type: Mixed population of aquatic microorganisms (activated sludge)
Origin: Secondary effluent of a domestic sewage treatment plant (Kläranlage Odenthal)
Date of collection: June 26, 1999
Pretreatment: None
Treatment given: Separation of coarse particles by filtration
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
19.1 mg/L
Based on:
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
DOC removal
(the biodegradation of the test substance was determined on the basis of the reduction in DOC)
Details on study design:
- Concentration of the stock solution: 1 g/L
- Initial concentration of test substance: 19.1 mg/L DOC
- Initial concentration of reference substance: 19.8 mg/L DOC
- Concentration of effluents in reaction mixture: 0.5 mL/L
- Temperature: 22±2°C

- Control (2 replicates)
- Test substance (2 replicates)
- Reference substance (2 replicates)
- Toxicity control (test and reference substance plus inoculum)

- Samples were taken for analysis on 0, 7, 14, 21, 27 and 28 d
- The DOC content in each reaction vessel was determined twice at each time point
Reference substance
Reference substance:
benzoic acid, sodium salt
(99% pure)

Results and discussion

% Degradation
% degradation (DOC removal)
Sampling time:
28 d
Details on results:
Degradation of test substance:
12% degradation after 7 d
6% degradation after 14 d
1% degradation after 21 d
1% degradation after 27 d
0% degradation after 28 d

BOD5 / COD results

Results with reference substance:
Degradation of reference substance:
96% degradation after 7 d
97% degradation after 14 d
98% degradation after 21 d
98% degradation after 27 d
100% degradation after 28 d

Any other information on results incl. tables

- The used concentrations of the test substance did not show toxic effects to bacteria.

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
other: not readily biodegradable
Under the study conditions, the test substance was considered to be ‘not readily biodegradable’.
Executive summary:

A study was conducted to assess the ready biodegradability of the test substance according to EU Method C.4-B, in compliance with GLP.

Activated sludge was inoculated with 19.1 mg/L (expressed in terms of dissolved organic carbon (DOC)) of the test substance (in duplicate) and incubated under aerobic conditions at a constant temperature (22±2°C) for 28 d. Degradation was assessed by the determination of DOC on Days 0, 7, 14, 21, 27 and 28. A control solution, a reference test (containing the reference substance benzoic acid, sodium salt (19.8 mg/L DOC) together with inoculum) and a toxicity test (containing the test substance, reference substance and the inoculum) were used for validation purposes.

The test substance degraded 0% by Day 28. No toxicity was observed in the toxicity control. The reference substance showed 97% degradation at Day 14.Under the study conditions, the test substance was considered to be ‘not readily biodegradable’.