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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2003-03-31 to 2003-07-21
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Remarks:
The testing facility indicated that the protocol was followed without deviations from guideline.
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Remarks:
The testing facility indicated that the protocol was followed without deviations from the guideline.
GLP compliance:
yes (incl. QA statement)
Remarks:
: from the Swiss GLP Monitoring Authorities
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Name of test material (as cited in study report): T002615
- Substance type: not applicable
- Physical state: solid white
- Analytical purity: > 98%
- Purity test date: no data
- Lot/batch No.: 00403487
- Expiration date of the lot/batch: December 2003 (retest date)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Stability under test conditions: no data
- Storage condition of test material: at room temperature at about 20 deg C, away from direct sunlight
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): activated sludge from a wastewater treatment plant ( ARA Ergoz II Füllinsdorf, Switzerland) treating predominantly domestic wastewater
- Laboratory culture: not applicable
- Storage conditions: at room temperature with aeration until use
- Preparation of inoculum for exposure: The sludge was washed out twice with tap water by centrifugation, 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 6 g (±10%) dry material per liter. During holding, the sludge was aerated at room temperature until use. Prior to use, the sludge was diluted with test water to a concentration of 1.5 g per liter (dry weight basis). The diluted activated sludge was used as inoculum to give a final concentration of 30 mg suspended solids per liter.
- Pretreatment: no data
- Concentration of sludge: 1.5 g per liter (dry weight basis)
- Initial cell/biomass concentration: no data
- Water filtered: purified water
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Initial conc.:
101 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: biochemical oxygen demand
Details on study design:
TEST CONDITIONS
- Composition of medium: the test medium (mineral medium) was prepared according to the testing guidelines
- Additional substrate: no
- Solubilising agent (type and concentration if used): not applicable
- Test temperature: 22 °C, maintained with a built-in thermostat and checked once per week
- 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 with a diluted hydrochloric acid or sodium hydroxide solution. At the end of incubation the pH was measured again in each test flask.
- pH adjusted: the pH was adjusted from 7.9 to 7.4 with a diluted hydrochloric acid solution).
- CEC (meq/100 g):no data
- Aeration of dilution water: no data
- Suspended solids concentration: 30 mg dry material per liter
- Continuous darkness: yes
- Other: The test water was prepared according to the testing guidelines. Analytical grade salts were dissolved in purified water to obtain the stock solutions.

TEST SYSTEM
- Culturing apparatus: 500 mL Erlenmeyer flasks
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: The consumed oxygen is replaced by electrolytically generated oxygen from copper sulfate solution.
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: 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 air-tight test flasks. The drop in pressure is detected and converted into an electrical signal by means of an electrode type manometer.
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: The CO2 is adsorbed by soda lime
- Other: no data

SAMPLING
- Sampling frequency: continious measurement

CONTROL AND BLANK SYSTEM
- Inoculum blank: two flasks used without the test substance or reference substance
- Abiotic sterile control:single flask containing 100 mg/L of the test substance poisoned with mercury dichloride at a concentration of 10 mg/L
- Toxicity control: single flask containing 101 mg/L of the test substance and 100 mg/L of the reference substance (sodium benzonate)
- Other: two procedure controls with 100 mg/L reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
Product No 71295; Lot No. 403453/1; Purity 99.6% (measured with Titration method); Storage Conditions: In tight closed container, at room temperature at about 20 deg C.
Test performance:
In the toxicity control more than 25% degradation occurred within14 days (41% and 33% based on the ThODNH4 and the ThODNO3, respectively). Therefore, the test substance was assumed to be not inhibitory on microbial activity.
The reference item was degraded by an anverage of 83% by exposure day 14, thus confirming suitability of the activated sludge.
Key result
Parameter:
other: % biodegradation (ThODNH4)
Value:
-4
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3 and 4
Key result
Parameter:
other: % biodegradation (ThODNO3)
Value:
-3
Sampling time:
28 d
Remarks on result:
other: mean of test bottle 3 and 4
Details on results:
The biochemical oxygen demand (BOD) of the test item T002615 in the test media was within the range of the inoculum controls. T002615 was found to be not biodegradable under the test conditions within 28 days.
Results with reference substance:
The percent degradation of the reference item, sodium benzonate, was determined to be 88% based on theoretical oxygen demand after 28 days.The reference item was degraded by an average of 83% by exposure day 14, thus confirming suitability of the activated sludge.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
A 28-d ready biodegradability test (OECD 301F) using unadapted activated sludge from a predominantly domestic waste water treatment plant indicated that T002615 was not readily biodegradable under the conditions of the test. The BOD of the test item T002615 in the test media was within the range of the inoculum controls. The test substance did not inhibit microbial activity at the concentration used in the test. The results of the test can be considered reliable without restriction.

Description of key information

One study (Grützner, 2003) is included in this dossier and regarded as a key study (Klimisch score of 1).  The biodegradability of T002615 was determined according to OECD Guideline 301F and EU Method C.4-D. Under the conditions of the test, T002615 was determined to be not biodegradable within 28 days.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information