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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Nov-Dec 2009
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: study conducted under GLP conditions and in acc. with OECD guideline

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Principles of method if other than guideline:
This·study differed in three points from the test protocol described in the OECD test
guideline 302 C:

• In the OECD 302 C guideline a toxicity control is not included

• The sludge was only from one site, not from ten different sites

• A slightly different test medium was used, since a 1.5 times higher
concentration of Na2HP04 was added. As this is the concentration of Na2HP04 added in
the medium of the OECD 301 tests, negative effects on the sludge can be excluded.
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
2,6-difluoro-3-(propane-1-sulfonamido)benzoic acid
EC Number:
Cas Number:
Molecular formula:
2,6-difluoro-3-(propane-1-sulfonamido)benzoic acid
Details on test material:
-Substance type: organic
-Physical state: solid

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum: Not adapted activated sludge from the aeration tank of the ARA Werdholzli (CH-8048 Zurich), a
municipal biological waste water treatment plant.
1 00 mg/1 dry matter in the final mixture.
Duration of test (contact time):
ca. 28 d
Initial test substance concentration
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The activated sludge was used after sampling from the treatment plant without
adaptation. However, the sludge was pre-conditioned for 1 day (aerated but not fed)
to reduce the amount of 0 2 consumed by the blank controls.
Prior to the test the sludge was washed twice with tap water. The test material was
directly added to the test solutions to give a final test concentration of about 30 mg/1.
The reference compound sodium benzoate was applied at a concentration of about
100 mg/1. In the toxicity control about 30 mg/1 test material and about 30 mg/1
reference material were applied simultaneously.
The test vessels were stirred by an inductive stirring system for a maximum test
period of 28 days. During the test the 0 2 uptake is continuously measured with a
manometric BOO measuring device. The pH-value was checked at the beginning
and at the end of the test and was adjusted to pH 7.2 (± 0.2) with NaOH or H2S04 at
the beginning of the test, respectively.
The biodegradation of the test material was followed by daily measurements.
Additionally, ultimate biodegradation was determined based on the theoretical
carbon content and the analyses of dissolved organic carbon (DOC) concentrations
at the end of the test.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradationopen allclose all
% degradation (O2 consumption)
Sampling time:
2 d
Remarks on result:
other: test unit no3
% degradation (O2 consumption)
Sampling time:
14 d
Remarks on result:
other: test unit no3
% degradation (O2 consumption)
Sampling time:
27 d
Remarks on result:
other: test unit no3

BOD5 / COD results

Results with reference substance:
79% biodegadability within 7 Days
86% biodegadability within 14 Days

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
not inherently biodegradable
Based on the data of the individual 02 determinations, no
biodegradability in the Modified MITI Test (11) of SAC-Sulfonamidsaure was observed during 28 days.
Executive summary:

The biodegradability of SAC-Sulfonamidsaure exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions in the Modified MITI Test (11). No biodegradability of SAC-Sulfonamidsaure based on 02 consumption was observed during 28 days as compared to the theoretical oxygen demand (ThOD). At the applied initial test concentration of 30.0 mg/1 the test substance showed no significant toxic effect on the microbial population, since the biodegradation of the mixture (test substance + reference compound sodium benzoate) was within the expected theoretical value during the whole test period. The procedure control sodium benzoate reached 79 and 86% biodegradation after 7 and 14 days, thus confirming suitability of inoculum and test conditions. The calculated elimination based on DOC measurement reached 5% for SACSulfonamidsaure and 99% for sodium benzoate. The data show that SAC-Sulfonamidsaure will not be retained in sewage treatment plants. Based on these results SAC-Sulfonamidsaure cannot be termed as inherently biodegradable in the Modified MITI Test (11), since less than 20% degradation was attained after 28 days of incubation.