Registration Dossier

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
Study period:
2001-01-08 to 2001-03-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: OECD guideline, GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report date:
2001

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: ARA Ergolz II, Füllinsdorf, Switzerland
- Method of cultivation: The sludge was washed once with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated. Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (±10%) dry material per liter.
- Storage conditions: aeration at room temperature
- Preparation of inoculum for exposure: The sludge was diluted with test water to a concentration of 1 g per liter (dry weight basis). This diluted activated sludge was used as inoculum to give a final concentration of 30 mg dry material per liter.
- Concentration of sludge: 30 mg dry material per liter

Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
100 mg/L
Based on:
test mat.
Initial conc.:
156 mg/L
Based on:
COD
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 22 °C
- pH:7.4
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 ml Erlenmeyer flasks
- Number of culture flasks: 7
- Other: The test flasks (500-ml Erlenmeyer flasks, labeled with all necessary information to assure unmistakable identification) were incubated under continuous stirring in a SAPROMAT D12 (Voith GmbH, Heidenhelm, Germany). Oxygen consumption was recorded manually by taking a daily reading at least on each working day.
Electro-chemical analysis process:
The biodegradation process consumes the dissolved oxygen in liquid and generates CO2. The CO2 is adsorbed by soda lime and the total pressure decreases in the airtight test flasks. The pressure drop is detected and converted into an electrical signal by means of an electrode type manometer.
The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulfate solution.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic control: poisoned with mercury dichloride
- Toxicity control: containing test item and reference item

Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (O2 consumption)
Value:
15
Sampling time:
28 d
Details on results:
The percent biodegradation of the test item was calculated based on the chemical oxygen demand (COD) of 0.156 mg O2/mg test item. The biochemical oxygen demand (BOD) of test item/C in the test media slightly increased from Day 5 until test termination on Day 28. At the end of the exposure period, the mean
biodegradation rate of test item/C amounted to 15%. Consequently, item/C was found to be very slightly biodegradable under the test conditions within 28 days.

BOD5 / COD results

BOD5 / COD
Parameter:
COD
Value:
0.156 mg O2/g test mat.
Results with reference substance:
The percent biodegradation of the reference item sodium benzoate was calculated based on the theoretical oxygen demand of 1.67 mg 02/mg (ThOD). In the procedure controls, the reference item was degraded by an average of 89% by exposure Day 14, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 94%.

Applicant's summary and conclusion