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Diss Factsheets

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
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: according to guideline and GLP, no deviations

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Reference substance name:
2,4-di-tert-butylphenyl diphenyl phosphite; 2-tert-butylphenyl diphenyl phosphite; 4-tert-butylphenyl diphenyl phosphite; triphenyl phosphite
EC Number:
Molecular formula:
2,4-di-tert-butylphenyl diphenyl phosphite; 2-tert-butylphenyl diphenyl phosphite; 4-tert-butylphenyl diphenyl phosphite; triphenyl phosphite
Test material form:
other: yellowish liquid
Details on test material:
purity 100%

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
21 mg/L
Based on:
test mat.
Initial conc.:
21.3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
- Composition of medium:
according to guideline
Stock solutions:
KH2PO4 8.5g/L
K2HPO4 21.75 g/L
Na2HPO4 x 2H2O 33.4g/L
NH4Cl 0.5g/L
MgSO4 x 7H2O 22.5g/L
CaCl2 x 2H2O 36.4 g/L
FeCl3 x 6H2O 0.25g/L + 1 drop concentrated HCl
Final test water (1000mL): 10mL solution a) + 1mL each of solution b)-d) + purified water
pH adjsuted to 7.4 with diluted hydrochloric acid solution

- Test temperature: 23-24°C
- pH: 7.4 day 0 after addtion of test item/refrence item
- Aeration: CO2 free air
- Suspended solids concentration: 30mg dry material per liter
- Continuous darkness: yes

- Culturing apparatus: 54-liter allglass amber bottles
- Number of culture flasks/concentration: 9 flasks: 2 test item, 2 for reference item, 2 for inoculum control, 1 abiotic control, 1 abiotic control blank, 1 toxicity control
- Method used to create aerobic conditions: 30-100mL/min CO2 free air

- Sampling frequency: Day 2, 5 9, 12, 14, 19, 23, 28, 29
- Sampling method: inorganic carbon analysis of aliquot 2mL from absorber flask (Shimadzu TOC-500 Analyser)
- Other: on Day 28 1mL concentrated HCl was added to each test flask for measurement of residual CO2 on day 29


- Abiotic control/abiotic control blank: 10mg/L mercury dichloride
- Toxicity control: 21.3 mg/L test item + 25.7 mg/L reference itemsodium benzoate

Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
% degradation (CO2 evolution)
Sampling time:
28 d
Details on results:
Biodegradation after 14 days: 34.5 - 25.6 %
Biodegradation after 28 days: 36.5 - 46.6%

The test item had no inhibitory effect on activated sludge microorganisms because the biodegradation rate in the toxicity control was >25%
within 14 days.

BOD5 / COD results

Results with reference substance:
In the procedure controls, the reference item was degraded by an average of 79.0% by bexposure Day 14, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 80.6%.
The biodegradation rate in the toxicity control showed a similar course over the 28-day exposure period as the two procedure controls containing the reference item, only. Within 14 days of exposure, a biodegradation rate of 70.4% was observed.

Any other information on results incl. tables

Maximum 1.85 mg C/L was found in the absorber flasks on day 29. Consequently, only negligible amounts of residual CO2 were present in the test solutions at the end of the test.

Applicant's summary and conclusion