Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report Date:
1992

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: bulk

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source: aeration stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.
- Preparation: the activated sludge was washed by repeatedly settling and resuspending with the test water.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
211 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Sludge usage Rate: equivaìent to 750 mg dry weight/l.
- Agitation: by magnetic stirrers and compressed air via narrow bore glass tubes.
- Temperature: 22 °C
- Continuous darkness: yes; the test was conducted in darkness.

SAMPLING
Losses by evaporatoin were made good by the addition of de-ionised water immediately prior to sampling.
20 ml samples were withdrawn from each vessel and filtered through 0.45 um disposable filters, the first 10 ml was discarded.
Assays were performed in triplicate.
Reference substance
Reference substance:
diethylene glycol

Results and discussion

% Degradation
Parameter:
% degradation (DOC removal)
Value:
33
Sampling time:
28 d

Applicant's summary and conclusion

Interpretation of results:
inherently biodegradable
Executive summary:

The test item was investigated for its biodegradability in the inherently Zahn-Wellens test over a period of 28 days. The substance was inoculed with a mixed population of activated sewage sludge microorganisms.

The substace attained 33 % degradation within 28 days, therefore can be considered as inherently biodegradable. The Standard Substance diethyleneglycol attained 100 % degradation within 27 days, confirmed on day 10, thereby confirming the suitability of the inoculum and culture conditions.

pH values did not drop below 5.2 in any culture vessel during the course of the study and were adjusted to pH 7.3 daily. Dissolved oxygen levels remained at approximately 7.0 mg O2/l or above in all cultures at all times.