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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
according to OECD guideline

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report Date:
2004

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
Secondary effluent of municipal biological waste water treatment plant, non-adapted, not pre-conditioned; source: ARA Werdhölzli, CH-8048 Zuerich
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
40 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: aerobic mineral salts medium, prepared with deionised water; conductivity < 1.5 µS/cm; DOC < 0.3 mg/L
- Test temperature: 22 ± 0.5°C
- pH: 7.4 ± 0.2
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: 1200 mL glass bottle containing a total volume of test solution of 800 mL
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: test vessels were stirred and aerated with CO2-free air for a maximum test period of 28 days.
- Measuring equipment: DOC was determined in duplicate with a SHimadzu 5050 TOC-Analyzer using the NPOC-mode. For each determination 3 single injections were performed.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradationopen allclose all
Parameter:
% degradation (DOC removal)
Value:
58
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
95
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
21 d

BOD5 / COD results

Results with reference substance:
97 % biodegradation of the reference substance sodium benzoate was observed after 14 days.

Any other information on results incl. tables

At the end of the test the pH value of both inoculum blanks and the procedure control was 7.3 and 7.4 respectively. The pH value of both test suspensions and the toxicity control was 8.2 respectively.

Complete biodegradation of the test substance was observed without any signiticant lag phase.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradability of the test item was calculated to be 99 % after 28 days of incubation. The test item reached the pass level of 70 % for ready biodegradability within the 10 day window and can therefore be termed as readily biodegradable. The procedure control sodium benzoate reached 97 % biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.