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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 2018-05-31 to 2018-07-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Purity: > 99%
Batch No.: 102Z4
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: the aeration tank of Shenyang North Sewage Treatment Plant
- Storage conditions: Keep the suspended sludge aerobic at 21.9 °C ~ 23.4 °C until the day of the test.
- Pretreatment: coarse particles were removed by filtration through a fine sieve and the sample was settled. After the supernatant was discarded, the sludge was washed twice with mineral medium and the concentrated sludge was suspended in mineral medium.
- Concentration of suspended sludge: 3438 mg/L as suspended solids (the measured concentration)
- Type and size of filter used, if any: a fine sieve
Duration of test (contact time):
28 d
Initial conc.:
20.21 mg/L
Based on:
test mat.
Remarks:
average, 2 replicates
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: potassium dihydrogen orthophosphate (KH2PO4), dipotassium hydrogen orthophosphate (K2HPO4), disodium hydrogen orthophosphate dihydrate (Na2HPO4·2H2O), ammonium chloride (NH4Cl), Calcium chloride dihydrate (CaCl2·2H2O), magnesium sulfate heptahydrate (MgSO4·7H2O), iron (III) chloride hexahydrate (FeCl3·6H2O)
- Test temperature: 22 °C ± 1 °C (actual temperature range 22.0 °C ~ 22.8 °C)
- Suspended solids concentration: 30 mg/L
- Continuous darkness: no, conducted in diffuse light.

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: magnetic stirring rod
- Measuring equipment: automated respirometer
- Details of trap for CO2 if used: Insert the magnetic stirring rod into the flasks, fill CO2 trap cuvette with 4 mL of 10 mol/L NaOH solution and push the cuvette on to the sensor head. Attach the test flasks to the sensor head.

CONTROL AND BLANK SYSTEM
- Inoculum blank: contained only 1 L inoculated mineral medium, prepared in duplicate
- Abiotic sterile control: 0.02041 g of test item was weighed into test flask and 900 mL of mineral medium with 100 ml of 3,5-dichlorophenol solution in mineral medium at the concentration of 500 mg/L was added.No inoculums were added to test flask which served as an abiotic sterile control identified as ASC. One replicate sufficed.
- Toxicity control: contained both test item (0.02078 g) and reference item (0.03156 g), one replicate sufficed.
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
5.7
Sampling time:
28 d
Remarks on result:
other: average, 2 replicate
Details on results:
The percentage biodegradation of test item after 28 days averaged 5.7% (2 replicate). The percentage degradation of the test item did not reach the pass level of 60% at the end of the test.
In the Toxicity Control (TC) test mixture, 40.8% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test.
In the Abiotic Sterile Control (ASC) Test Vessel, 18.7% degradation occurred after 28 days.
Results with reference substance:
Biodegradation of the reference substance attained 64.2% after Day 5, 95.3% after Day 14 and 93.6% after Day 28.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item is not readily biodegradable under the described test conditions.
Executive summary:

The ready biodegradability test of the test substance was conducted with unacclimatised sewage micro-organism by measuring oxygen consumption over the 28-day test period according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test).

The test item was added directly to test vessels at a level of 20.21 mg/L (average, 2 replicate).The test concentration of sodium benzoate, used as reference substance in the Procedure Control, was 31.24 mg/L. In the Toxicity Control (TC) containing both test item and reference substance, the test item was added to the test vessel at a level of 20.78 mg/L and the reference substance was added at a level of 31.56 mg/L of sodium benzoate, the concentration expressed as total ThOD was 105.91 mg/L. In the Abiotic Sterile Control (ASC) Test Vessel without inoculums addition and 3,5-dichlorophenol of 50 mg/L,the test item was added to the test vesselat a level of 20.41 mg/L.

The percentage biodegradation of test item after 28 days averaged 5.7% (2 replicate). The percentage degradation of the test item did not reach the pass level of 60% at the end of the test. Biodegradation of the reference substance (Sodium benzoate) attained 64.2% after Day 5, 95.3% after Day 14 and 93.6% after Day 28. In the Toxicity Control (TC) test mixture, 40.8% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. In the Abiotic Sterile Control (ASC) Test Vessel, 18.7% degradation occurred after 28 days.

Based on these results, the test item is not readily biodegradable under the described test conditions.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
From 2017-07-25 to 2017-08-22
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Purity: > 99%
Batch No.: 101Z4
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum: carried out at 10 locations (samples were from surfacewater and surface soil of rivers, lake and inland sea, and retum sludge from sewage plants).
- Method of cultivation: cultivated for 19 hours after feeding with the synthetic sewage
- Concentration of suspended solid in the activated sludge: 3860 mg/L (measured concentration)
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Parameter followed for biodegradation estimation:
test mat. analysis
Details on study design:
TEST CONDITIONS
- Composition of medium: purified water was added to each 3 mL aliquot of solutions A (KH2PO4, K2HPO4, Na2HPO4.12H2O, NH4Cl), B (MgSO4.7H2O), C (CaCl2) and D (FeCl3.6H2O)
- Test temperature: 25 ± 1 °C (measured value: 25.0 °C)
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 3
- Measuring equipment: closed system oxygen consumption measuring apparatus, temperature controlled bath with measuring unit
- Test performed in closed system : yes
- Details of trap for CO2 if used: use Soda lime NO.1 for absorption of carbon dioxide

CONTROL AND BLANK SYSTEM
- Inoculum blank: only basal culture medium
- Abiotic control: water + test item
- Program control: sludge + reference substance
Reference substance:
aniline
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Key result
Parameter:
% degradation (test mat. analysis)
Value:
0
Sampling time:
28 d
Details on results:
The average percentage biodegradation by BOD and that by HPLC were both 0%. There was no change in the peak shape of the test item and no peak of degradation products on the HPLC chromatograms for detemination of the test item.
Results with reference substance:
The percentage biodegradation by BOD was 72% on the 7th day, 92% on the 14th day.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test item was not biodegraded under the test conditions of this study.
Executive summary:

The ready biodegradability test of the test substance was conducted over the 28-day test period according to OECD Guideline 301C (Ready Biodegradability: Modified MITI Test (I)).

The test item and the activated sludge were added to the basal culture medium, then the mixture was stirred with a stirrer for 28 days under dark conditions. During the incubation period, BOD of the test solutions was measured continuously by a closed system oxygen consumption measuring apparatus. After the end of the incubation, the test item was analyzed quantitatively by HPLC.

The average percentage biodegradation by BOD and that by HPLC were both 0%. There was no change in the peak shape of the test item and no peak of degradation products on the HPLC chromatograms for detemination of the test item. The above results showed that the test item did not undergo biodegradation and remained under the test conditions.

The test item was not biodegraded under the test conditions of this study.

Description of key information

For this endpoint two studies are available.

In a study to OECD guideline 301 F (Ready Biodegradability: Manometric Respirometry Test), it was found that the percentage biodegradation of test item after 28 days averaged 5.7% (2 replicate). The test substance is therefore not considered to be readily biodegradable.

In a study to OECD guideline 301C (Ready Biodegradability: Modified MITI Test (I)), it was found that the average percent degradation of the test item by BOD and that by HPLC were both 0%. The substance was not biodegraded.


Key value for chemical safety assessment

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

Additional information

Key study: The ready biodegradability test of the test substance was conducted with unacclimatised sewage micro-organism by measuring oxygen consumption over the 28-day test period according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test).

The test item was added directly to test vessels at a level of 20.21 mg/L (average, 2 replicate). The test concentration of sodium benzoate, used as reference substance in the Procedure Control, was 31.24 mg/L. In the Toxicity Control (TC) containing both test item and reference substance, the test item was added to the test vesselat a level of 20.78 mg/L and the reference substance was added at a level of 31.56 mg/L of sodium benzoate, the concentration expressed as total ThOD was 105.91 mg/L. In the Abiotic Sterile Control (ASC) Test Vessel without inoculums addition and 3,5-dichlorophenol of 50 mg/L, the test item was added to the test vessel at a level of 20.41 mg/L.

The percentage biodegradation of test item after 28 days averaged 5.7% (2 replicate). The percentage degradation of the test item did not reach the pass level of 60% at the end of the test. Biodegradation of the reference substance (Sodium benzoate) attained 64.2% after Day 5, 95.3% after Day 14 and 93.6% after Day 28. In the Toxicity Control (TC) test mixture, 40.8% degradation occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test item can be assumed to be not inhibitory under the conditions of this test. In the Abiotic Sterile Control (ASC) Test Vessel, 18.7% degradation occurred after 28 days.

Based on these results, the test itemis not readily biodegradable under the described test conditions.

Support study: The ready biodegradability test of the test substancewas conducted over the 28-day test period according to OECD Guideline 301C (Ready Biodegradability: Modified MITI Test (I)).

The test item and the activated sludgewere added tothe basal culture medium, then the mixture wasstirred with a stirrer for 28 days under dark conditions. During the incubation period, BOD of the test solutions was measured continuously by a closed system oxygen consumption measuring apparatus.After the end of the incubation, the test item was analyzed quantitatively by HPLC.

The average percentage biodegradation by BOD and that by HPLC were both 0%. There was no change in the peak shape of the test item and no peak of degradation productson the HPLC chromatograms for detemination of the test item. The above results showed that the test item did not undergo biodegradation and remained under the test conditions.

The test item was not biodegraded under the test conditions of this study.