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Environmental fate & pathways

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:
December 12, 2006 - February 26, 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
adopted July 17, 1992
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
July 31, 1992
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
The activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. This procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 1.5 g dry material per litre were mixed with test water and then aerated until use overnight.
Duration of test (contact time):
28 d
Initial conc.:
102 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Temperature: 22°C
Light conditions: darkness
pH: 7.6 (start), 7.7 - 7.9 (end)

The amounts of test item and reference item were directly weighed into the test flasks. No emulsifiers or solvents were used, but the solutions were dispersed by stirring to achieve a homogeneous solution of the test item. The closed test flasks were incubatd in a climatised room under contiuous stirring.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
-6
Sampling time:
28 d
Details on results:
Under the test conditions no biodegradation of the test item could be observed.
Results with reference substance:
The reference item sodium benzoate was sufficiently degraded to 87 % after 14 days and to 90 % after 28 days of incubation, thus confirming the suitability of the used activated sludge inoculum.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item is not considered to be readily biodegradable.
Executive summary:

Purpose

The test item was investigated for its ready biodegradability in a Manometric Respirometry Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item aniline was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. The GLP study was performed according to OECD TG 301F.

Result

Biodegradation of test item

Under the test conditions no biodegradation of the test item could be observed. The degradation rate of the test item did not reach 60 % within the 10 day window and after 28 days of incubation of incubation. Therefore, the test item is not considered to be readily biodegradable.

Biodegradation of Sodium Benzoate

The reference item sodium benzoate was sufficiently degraded to 87 % after 14 days and to 90 % after 28 days of incubation, thus confirming the suitability of the used activated sludge inoculum.

Biodegradation in the Toxicity Control

In the toxicity control containing both, the test item and the reference item sodium benzoate, 31% biodegradation was noted within 14 days and 33% biodegradation was detremined after 28 days of incubation. Thus, the test item can be assumed to be not inhibitory on the activated sludge microorganisms because degradation was >25% within 14 days.

Conclusion

The test item is not considered to be readily biodegradable.

Description of key information

The information for this endpoint study record was obtained from an experimental study. The OECD GLP criteria were met and the methods applied are fully compliant with OECD TG 301F. In this study, the test material was not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information