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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:
February 16 - April 26, 2010
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
The study was performed in compliance with the Good Laboratory Practice (GLP) regulations (revised in 1997, ENV/MC/CHEM(98)17). The method followed that described in the OECD Guidelines for Testing of Chemicals (Adopted: 1992) No 301F "Ready Biodegradability: Manometric Respirometry Test".

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
according to
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. certificate)

Test material

Details on test material:
Name: Phenolphthalein
Purity: 99.9 %

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
activated sludge from a domestic waste water treatment plant
Duration of test (contact time):
>= 28 d
Initial test substance concentration
Initial conc.:
105 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
according to guideline
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
see executive summary
% Degradation
% degradation (O2 consumption)
Sampling time:
28 d
Details on results:
see executive summary

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
readily biodegradable, but failing 10-day window
The test item was found to be readily biodegradable, but failing 10-day window.
Executive summary:


The purpose of this assay was to provide information on the biodegradability of the test item in aqueous environment and thus serve as a rational basis for risk assessment for environmental fate in aqueous compartments.

Study Design

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 micro organisms during exposure. As a reference item Aniline was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.


Biodegradation of the test item

After correction of the mean biochemical oxygen demand of the inoculum controls at the end of the 28-day exposure period degradation rates of 75 % and 76 % were found.

Biodegradation of Reference item

The reference item sodium benzoate was sufficiently degraded to 88 % after 14 days, and to 96 % after 28 days of incubation.

The percentage biodegradation of the reference item confirms 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, 37 % biodegradation was noted within 14 days and 64 % biodegradation was determined after 28 days of incubation. According to the test guidelines the test item can be assumed to be not inhibitory on the activated sludge micro organisms because degradation was > 25 % within 14 days.


The degradation rate of Phenophthalein did reach 76 % after 28 days of incubation. The test item was found to be readily biodegradable, but failing 10-day window.