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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
adopted 17. Jul. 1992
Deviations:
yes
Remarks:
see "Principles of method if other than guideline" for information on deviation
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
adopted 30. May 2008
Deviations:
yes
Remarks:
see "Principles of method if other than guideline" for information on deviation
Qualifier:
according to
Guideline:
other: SOP 118 00 615 "Abbaubarkeit nach OECD 301F"
Version / remarks:
edition 5 valid from 02. May 2014
Deviations:
yes
Remarks:
see "Principles of method if other than guideline" for information on deviation
Principles of method if other than guideline:
Temperature range was 19.6 - 23.1 °C instead of 20.0 - 24.0 °C. As degradation of the positive control was in the normal range, this is considered as uncritical concerning the outcome of the study.
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge from a biologic sewage treatment plant was used. The chosen plant is treating mostly household sewage. The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
- Pretreatment: The sludge was filtrated, washed with tap water twice, then washed with and resuspended in test medium. It was then aerated.
The dry matter was determined as 3120 mg suspended solids/L.
Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
57 mg/L
Based on:
test mat.
Initial conc.:
88.25 mg/L
Based on:
ThOD
Remarks:
without nitrification
Initial conc.:
99.98 mg/L
Based on:
ThOD
Remarks:
with nitrification to nitrate
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium:
Stock solutions
a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4 x 2 H2O, 0.5 g NH4Cl and 1000 mL H2O demin. ad
b) 27.5 g CaCl2 x 2H2O and 1000 mL H2O demin. ad
c) 22.5 g MgSO4 x 7H2O and 1000 mL H2O demin. ad
d) 0.25 g FeCl3 x 6H2O, 0.4 g Na2EDTA x 2H2O and 1000 mL H2O demin. ad
Test Medium
10 mL solution a
1 mL solution b
1 mL solution c
1 mL solution d
1000 mL H2O demin. ad
- Test temperature: 19.6 - 23.1 °C
- pH: 7.4-7.5
- pH adjusted: yes
- Suspended solids concentration: 25 mg/L

TEST SYSTEM
- Number of culture flasks/concentration: 3 (test item, medium and inoculum)
- Other:
Volume of test vessels: 500 mL
Volume test solution: 250 mL (toxicity control flask 125 mL)

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 (medium and inoculum)
- Abiotic sterile control: 1 (test item and 10 mL 1% HgCl2 solution)
- Toxicity control: 1 (200 mg/L ThOD, 100 mg/L ThOD each of test item and positive control)
- Other: Number of positive control vessels: 3 (sodium benzoate, medium and inoculum)
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Test performance:
No observations were made which might cause doubts concerning the validity of the study outcome.
% Degradation
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
Degradation after 3 days > 60% (validity criterion fulfilled)
Positive control 1: 86.7 % degradation after 28 days
Positive control 2 & 3: 87.7 % degradation after 28 days

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The study was performed according to OECD TG301F and EU Method C.4-D (GLP) with only minor deviation uncritical concerning the outcome of the study and therefore considered to be of the highest quality (reliability Klimisch 1). The validity criteria of the test system are fulfilled. Within 28 days, no degradation (0%) was determined for the test substance. Therefore, the test substance is considered to be not readily biodegradable.
Executive summary:

The biodegradability of the test substance was investigated according to EU method C.4 -D and OECD guideline 301 F (GLP). A measured volume of inoculated mineral medium, containing the test item in a concentration of 57 mg/L (corresponding to a ThOD of 99.98 mg O2/L), was stirred in a closed flask at a constant temperature for up to 28 days. Activated sludge from a biologic sewage treatment plant was used as inoculum. The chosen plant is treating mostly household sewage. Analytical grade salts were added to deionised water to prepare the stock solutions. Sodium benzoate was used as positive control. Also a toxicity control (test item and positive control mixed) and an abiotic control (test item and 10 mL 1% HgCL2 solution/L) was run in parallel, to ensure, that the chosen test concentration was not inhibitory to microorganims. The degradation rate of the test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

Oxygen consumption in the blank controls and in the positive controls was normal, indicating that the test system has worked properly.

Ready biodegradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10%. No degradation was observed within the test duration of 28 days. Therefore, the test item 3-(2-Benzothiazolylthio)-propanesulfonic acid, sodium salt can be considered as “not readily biodegradable”.

If degradation in the toxicity flask is below 25% after 14 days, the test item can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 42.2 % after 14 days, the test item can be stated as “not toxic towards the inoculum in a concentration of 57 mg/L”.

No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.