Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met. Minor deviation not considered to have impacted the interpretation of the study.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
Minor deviation: Due to incomplete seal to flask, blank control flask 2 was discarded. This was not considered to impact the interpretation of the results as the blank control flask 1 oxygen uptake was in the expected range 20 - 30 mg O2/L (d-28)
GLP compliance:
yes (incl. certificate)
Remarks:
inspected: February 2011; signature: September 2011
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): A mixed population of activated sewage sludge micro-organisms (Test System) was obtained from the secondary treatment stage of the sewage treatment plant at Villette (Geneva, Switzerland)), which treats predominantly domestic sewage.
- Storage conditions: See pretreatment field.
- Storage length: < 1 week
- Preparation of inoculum for exposure:
- Pretreatment: The sample of activated sewage sludge was maintained on continuous aeration upon receipt. A sample of the activated sewage sludge was washed three times by settlement (centrifuge) and suspension in culture medium. To remove any excessive amounts of Dissolved Organic Carbon (DOC) that may have been present, the solution was stirred and maintained on with pure oxygen at room temperature. Determination of dry weight is made to inoculate final solution with 30mg/L dry weight activated sludge.
- Concentration of sludge: The sludge was diluted in the BOD bottles to 30 mg DW/L.
Duration of test (contact time):
28 d
Initial conc.:
100.35 mg/L
Based on:
other: Test material (test 1)
Initial conc.:
100.2 mg/L
Based on:
other: Test material (test 2)
Initial conc.:
99.95 mg/L
Based on:
other: Test material (test 3)
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: See table 1. 10 mL of Solution A [KH2PO4: 8.50 g/L; K2HPO4: 21.75g/L; Na2HPO4,2H2O: 33.40 g/L; NH4Cl: 0.50 g/L]; 1 mL of Solution B [CaCl2,2H2O: 36.40 g/L]; 1 mL of Solution C [MgSO4,7H2O: 22.50 g/L]; 1 mL of Solution D [FeCl3,6H2O: 0.25 g/L] and purified water diluted to 1 L.
- Solubilising agent (type and concentration if used): None.
- Test temperature: 22 ±1 °C
- pH: See table 1.
- pH adjusted: No. (final pH was in the range of 7.34 to 7.37 for test item vessels)
- Aeration of dilution water: Not reported
- Suspended solids concentration: 30 mg/L dry weight
- Continuous darkness: No. The test was conducted in diffuse light.

TEST SYSTEM
- Culturing apparatus: 1000mL glass flasks with continuous stirring (fill volume ca. 200 mL)
- Number of culture flasks/concentration: In triplicate (test item); In duplicate (Inoculum blank); single flasks (Abiotic Sterile Control and toxicity control)
- Method used to create aerobic conditions: Sealed flasks wth sensor head/CO2 trap.
- Measuring equipment: The respirometer used during this study is an Oxitop Control System (WTW oxitopC). Evolved carbon dioxide is absorbed by the CO2 trap.

SAMPLING
- Sampling frequency: Daily.
- Sampling method: The respirometer used during this study is an Oxitop Control System.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes. See table 1.
- Abiotic sterile control: Yes.
- Toxicity control: Yes.
- Other: Positive reference control (Sodium Benzoate).
Reference substance:
benzoic acid, sodium salt
Remarks:
100.35 mg/L
Test performance:
1. The repeatability validity criterion (not more than 20% difference between replicates) is fulfilled for the flasks containing test substance at end of 10-day window and on day 28. Therefore, the test is considered valid.
2. The BOD of the inoculated blank control was 24.8 mgO2/L and < 60 mgO2/L after 28 days
3. The pH at day 28 was in the range of 6.0 to 8.5 (actual 7.34 to 7.37 for test item vessels)
4. The toxicity test attained 75% degradation after 14 days thereby confirming that the test material was not toxic to the sewage treatment microorganisms used in the study.
5. Sodium Benzoate attained 93% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions.

Applicant assessment indicates that blank control flask 2 - had to be discarded due to incomplete seal of the flask. The blank control flask 1 was used for all calculations. This was not considered to impact the interpretation of the study.
Parameter:
% degradation (O2 consumption)
Value:
98
Sampling time:
28 d
Remarks on result:
other: test 1; 10-day window met
Parameter:
% degradation (O2 consumption)
Value:
85
Sampling time:
28 d
Remarks on result:
other: test 2 ; 10-day window met
Parameter:
% degradation (O2 consumption)
Value:
91
Sampling time:
28 d
Remarks on result:
other: test 3 ; 10-day window met
Details on results:
The 10-day window criteria was met in all replicates (between start day 1, 2, 1 and end day 7, 10 and 8 in test 1, 2 and 3, respectively)
Results with reference substance:
Sodium Benzoate attained 93% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The mean biodegradation in triplicate was 91.3 % at day 28. The 10-day window criteria was met.
Executive summary:

The ready biodegradability test was carried out according to OECD TG 301F guideline under GLP. The test substance, at a concentration of 100.35 mg/L in test 1, at a concentration of 100.2 mg/L in test 2 and at a concentration of 99.95 mg/L in test 3 was exposed to activated sewage sludge micro-organisms obtained from the secondary treatment stage of the sewage treatment which treats predominantly domestic sewage (Villette: Geneva, Switzerland) with culture medium in sealed culture vessels in diffused light at 22°C ± 1°C for 28 days. The sludge was diluted in the BOD bottles to 30 mg DW/L. The degradation of the test substance was assessed by the measurement of daily oxygen consumption on days 0 and 28 using an Oxitop control system. Control solutions with inoculum and the reference substance, sodium benzoate, together with a toxicity control were used for validation purposes. In the test inoculum blank the oxygen uptake was < 30 mg O2/L. The pH value at the end of the test period 28 days did not exceed 7.47 in the test item systems and 7.54 in the reference item system. The test system met the validation criteria of the guideline. The toxicity test attained 75% degradation after 14 days thereby confirming that the test substance was not inhibitory to the sewage treatment micro-organisms used in the study. Sodium Benzoate attained 93% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions. The mean biodegradation for triplicate test flasks at 28 days for the test substance was 91.3% and the 10-day window was met. Under the conditions of the study, test item is considered as readily biodegradable.

Description of key information

Biodegradation: mean biodegradation 91.3 % (28-days; 10-day window met), OECD TG 301F, 2017

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

OECD TG 301F, 2017 - The ready biodegradability test was carried out according to OECD TG 301F guideline under GLP. The test substance, at a concentration of 100.35 mg/L in test 1, at a concentration of 100.2 mg/L in test 2 and at a concentration of 99.95 mg/L in test 3 was exposed to activated sewage sludge micro-organisms obtained from the secondary treatment stage of the sewage treatment which treats predominantly domestic sewage (Villette: Geneva, Switzerland) with culture medium in sealed culture vessels in diffused light at 22°C ± 1°C for 28 days. The sludge was diluted in the BOD bottles to 30 mg DW/L. The degradation of the test substance was assessed by the measurement of daily oxygen consumption on days 0 and 28 using an Oxitop control system. Control solutions with inoculum and the reference substance, sodium benzoate, together with a toxicity control were used for validation purposes. In the test inoculum blank the oxygen uptake was < 30 mg O2/L. The pH value at the end of the test period 28 days did not exceed 7.47 in the test item systems and 7.54 in the reference item system. The test system met the validation criteria of the guideline. The toxicity test attained 75% degradation after 14 days thereby confirming that the test substance was not inhibitory to the sewage treatment micro-organisms used in the study. Sodium Benzoate attained 93% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions. The mean biodegradation for triplicate test flasks at 28 days for the test substance was 91.3% and the 10-day window was met. Under the conditions of the study, test item is considered as readily biodegradable.