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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:
2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Guideline study performed under GLP. All relevant validity criteria were met.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Remarks:
Replicate 2 (of 3) was disguarded due to a technical problem. Guideline specifies tests to be 'at least in duplicate' not considered a major deviation.
GLP compliance:
yes (incl. certificate)
Remarks:
inspected September 2013; signature: February 2014
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
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.:
>= 101.35 - <= 101.95 mg/L
Based on:
test mat.
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.- Aeration of dilution water: Not reported- Continuous darkness: No. The test was conducted in diffuse light.TEST SYSTEM- Culturing apparatus: Flasks with continuous stirring.- 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 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:
104.45 mg/L
Test performance:
The repeatability validity criterion (not more than 20% difference between replicates) is fulfilled for the flasks containing test substance. Therefore, the test is considered valid. Test 2 (of 3) was discarded due to techncial problem. The deviation in these values was attributed to a technical problem during the test (i.e. the cap was not airtight). Hence, the results related to this replicate have been disregarded. This is not considered to have influenced the outcome of the test or the global interpretation of the results.
Parameter:
% degradation (O2 consumption)
Value:
64
Sampling time:
28 d
Remarks on result:
other: mean biodegradation (n = 2): test 1: 61%; test 2: 36% and test 3: 67%. Test replicate 3 disregarded ; see 'details on results'
Details on results:
The test material (test 1) attained 61% degradation after 28 days. 10-day window not met.The test material (test 2) attained 36% degradation after 28 days. Discarded due to technical problem.The test material (test 3) attained 67% degradation after 28 days. 10-day window not met.
Results with reference substance:
Degradation of sodium benzoate exceeded 64% after 2 days and 73% after 5 days: the activity of the inoculum was thus verified (validity criterion).

Acceptability criteria:

1. The results of the degradation test are considered valid if in the same test the reference material yields > 60% degradation by Day 14.

2. The test item may be considered to be readily biodegradable if > 60% degradation is attained after 28 days. This level of degradation must be reached within 10 days of biodegradation exceeding 10%.

3. The toxicity control should attain > 25% degradation by Day 14 for the test item to be considered as non-inhibitory.

 

Results:

1. Degradation of reference material (sodium benzoate) exceeded 64% after 2 days and 73% after 5 days: the activity of the inoculum was thus verified.

2. The test item (test 1) attained 61% and (test 3) 67% degradation after 28 days and didn't satisfy the 10-day window validation criterion. Test 2 results were discarded due to a technical problem.

3. The toxicity control test attained 46% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions

 

The test item did not exhibit a percentage biodegradation exceeding the pass level of 60% within 10-day window. However, the test item is a multi-constituent substance composed of two structurally similar constituents and therefore the 10-day window is not applied (UN GHS 4th edition, 2011 and OECD, 2006).

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance mean biodegradation in duplicate was 64 % at day 28.
Executive summary:

The ready biodegradability test was carried out according to OECD TG 301F guideline under GLP. The test substance, at a concentration of 107.80 mg/L in test 1, at a concentration of 101.35 mg/L in test 2 and at a concentration of 101.95 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. The oxygen uptake was < 38.4 mg O2/L in all of the test systems and the pH value at the end of the test period 28 days did not exceed 7.34. The test system therefore met the validation criteria of the guideline. Test 2 was discarded due to a technical problem and the results are reported in duplicate. The toxicity test attained 46% 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 73% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions. The mean biodegradation for duplicate test flasks at 28 days for the test substance was 64% however the 10-day window was not met. The test item did not exhibit a percentage biodegradation exceeding the pass level of 60% within 10-day window. However, the test item is a multi-constituent substance composed of two structurally similar constituents and therefore the 10-day window is not applied (UN GHS 4th edition, 2011 and OECD, 2006). Under the conditions of this study, this substance should be classified as readily biodegradable.

Description of key information

Biodegradation: mean biodegradation 64% (28-days; 10-day window does not apply - OECD 2006) readily biodegradable, OECD TG 301F, 2015

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

OECD TG 301F, 2015 - The ready biodegradability test was carried out according to OECD TG 301F guideline under GLP. The test substance, at a concentration of 107.80 mg/L in test 1, at a concentration of 101.35 mg/L in test 2 and at a concentration of 101.95 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. The oxygen uptake was < 38.4 mg O2/L in all of the test systems and the pH value at the end of the test period 28 days did not exceed 7.34. The test system therefore met the validation criteria of the guideline. Test 2 was discarded due to a technical problem and the results are reported in duplicate. The toxicity test attained 46% 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 73% degradation after 14 days thereby confirming the suitability of the inoculum and test conditions. The mean biodegradation for duplicate test flasks at 28 days for the test substance was 64% however the 10-day window was not met. The test item did not exhibit a percentage biodegradation exceeding the pass level of 60% within 10-day window. However, the test item is a multi-constituent substance composed of two structurally similar constituents and therefore the 10-day window is not applied (UN GHS 4th edition, 2011 and OECD, 2006). Under the conditions of this study, this substance should be classified as readily biodegradable.

References:

1. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7b: Endpoint Specific Guidance, R.7.9.4.1, November 2014)

2. Introduction to the section of the OECD Guidelines for Testing of Chemicals on Degradation and Accumulation, Section 3 (OECD, September 2006)

3. ECHA Guidance on Application on the CLP Criteria, section 4.1.3.2.3.2 (v4.1, June 2015)