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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
Study period:
November 12, 2007 - December 11, 2007
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: study conform with Directive 92/69 EEC, C.4-A

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Details on test material:
Identity: AES
Batch no.: LSF7
Expiration date: February 15, 2008
Purity: 80.3%
Stability in water: Max. 30 days at room temperature
Solubility in water: Very soluble
Aggregate state / physical
form at room temperature: Solid
Storage conditions: In the refrigerator at about 4 °C.
Specific instructions: Slightly hygroscopic

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: ARA Ergolz II, Füllinsdorf / Switzerland
and ARA Ergolz I, Sissach / Switzerland
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
29.4 mg/L
Based on:
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
Test vessels: 2000-mL Erlenmeyer flasks, cleaned with alcoholic hydrochloric acid, rinsed with
deionized water and dried. The final volume was 1000 mL per flask. Each flask was loosely
covered with aluminum foil to allow the exchange of air between the flask and the surrounding atmosphere.
The test media were continuously stirred by magnetic stirrers.

Identification: The test vessels were labeled with all necessary information to ensure unmistakable identification.

Test duration: 28 days

Test temperature: 21 - 24 °C. The inoculated flasks were incubated in a temperature-controlled room.
The temperature was checked on each sampling date (see Section 3.5) in one of the inoculum
controls. Additionally, the room temperature was continuously recorded.

pH: Prior to test start, the pH was measured in each test flask before the addition of the activated sludge
inoculum and, if necessary, adjusted to pH 7.4 with a diluted hydrochloric acid solution. At the end of
incubation, the pH was measured again in each test flask (Table 3).

Light conditions: The test flasks were incubated in a dark room.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
% degradation (DOC removal)
Sampling time:
28 d
Details on results:
In the toxicity control, containing the test item (corresponding to 57% of total DOC), the reference item (corresponding to 43% of total DOC) and activated sludge (inoculum), the initial DOC concentration of 68 mg/L measured on Day 0 decreased to 35 mg/L by Day 14. Biodegradation amounted to49% within 14 days of exposure. Thus, according to the test guidelines, the test item was not inhibitory to activated sludge at the tested concentration of 121 mg/L because degradation was >35% within 14 days.

BOD5 / COD results

Results with reference substance:
In the procedure controls, containing the reference item sodium benzoate and activated sludge (inoculum), sodium benzoate was completely biodegraded (>90%) within the first three days of exposure, thus confirming suitability of the activated sludge.

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
under test conditions no biodegradation observed
AES was not biodegradable under the test conditions.
Executive summary:

In the test flasks, containing the test item and activated sludge (inoculum), the mean concentration of DOC (dissolved organic carbon) only slightly decreased from initially 35 mg/L on Day 0 to 29 mg/L on Day 28 . The mean biodegradation of AES based on DOC decrease amounted to 16%.