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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:
From 28 December, 2020 to 28 January, 2021
Reliability:
1 (reliable without restriction)
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Remarks:
For the preparation of the inoculum a sample of aerobic sludge has been selected by the mixed treatment plant of urban (about 66%) and industrial (about 34%) liquid sewage situated at San Rocco - Monza(MI).
Details on inoculum:
ASSAY SYSTEM
Method of mud sampling
Biodegradability of a substance is based on different parameters, and among them composition and
concentration of bacterial biomass play an importantrole.
For the preparation of the inoculum a sample of aerobic sludge has been selected by the mixed
treatment plant of urban (about 66%) and industrial (about 34%) liquid sewage situated at San Rocco - Monza(MI).
The plant of treatment is managed by “BRIANZACQUE SRL(Monza)”.

Mud preparation
In the laboratory, muds have been mixed and let settle, keeping them in medium and in aerobic
conditions for up to 5-7 days.
Mud samples, before their use, have been centrifuged, washed and analyzed to quantify the
suspended solids concentration for the inoculum preparation.
Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 53.7 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
ASSAY EXECUTION
Conditions of assay execution
In every bottle so prepared potassium hydroxide (a CO2 absorber) has been added to the CO2 — absorber compartment.
Then the bottles, after 1 hour of equilibration, have been closed and incubation started understirring in darkness at 22°C + 2 °C for 28 days.
One time/week the values on the automatic respirometer the bottles of blank, reference substance and test item have been recorded.

Determination of dissolved oxygen
The respirometric measurement is a pressure measurement. If the oxygen is consumed in a closed vessel at a constant temperature, a negative pressure develops. If a gas is released, an overpressure develops. The Oxitop -C measuring head measures and stores this pressure for the whole duration of a measurement once started. This system controller collects the pressure values from the measuring heads and then process them.
Reference substance:
benzoic acid, sodium salt
Remarks:
Reference substance: Sodium benzoate - Supplier: Sigma Aldrich - Batch: SLBW2610 - Expiry date: 03/2021
Parameter:
% degradation (O2 consumption)
Value:
ca. 67
Sampling time:
28 d

EXPRESSION OF RESULTS
The calculation of biodegradation has been done at every sampling time for the reference substanceor test item subtracting the oxygen depletion of the blank.
Total biodegradation has been calculated using the following equations:


BODt = mg O2 test item/L — mg O2 blank /L


%D = BODt/ThOD x 100


Where:
BODt= biochemical oxygen demand is the amount of oxygen consumed by microorganisms when metabolizing the test item; also expressed as mg oxygen uptake per liter. These values are reported on the Oxitop system.
ThOD = theoretical oxygen demand is the total amount of oxygen required to oxidize a chemical completely; it's calculated from the molecular formula and is expressed as mg oxygen per mg test item. In this case is referred to the total mg ofthe test item presentin the bottles ThOD (mg O2/L).
%D = biodegradation percentage of the substanceor of the reference substance.
The same calculations have been performed for the reference substance.
For the test item the theoretical oxygen demand (ThOD) has been calculated by the elemental composition as follows


ThODNH3 = [16 x (2c + 1/2(h - cl - 3n) + 3 s + 5/2p + 1/2na - o) mg/mg]/ MW


 


VALIDITY CRITERIA
The test is considered valid when:
- the percentage of average biodegradation of the reference substance is more than 60%after 14 days of incubation;
- the difference of extremesof replicate values of the removal of the test item at the plateau, at the end of the test, is less than 20%;
- the oxygen uptake of the inoculum blank isn’t greater than 60 mg O2/L;
- the pH values of the test substance at the end ofthe test is in the range 6-8.5.



INTERPRETATION OF RESULTS
A substance is considered readily biodegradable when its level of biodegradability is at least 60%, within 10-d windowduring the test.



VALIDITY CRITERIA: CONFORMITY
Quality criteria of the test have been satisfied (see Attachment N. 2)
The oxygen uptake of the blank at the end of the test has been: 14.1 mg O2/L.
pH at the end of the test has been remainedin the range required (see table below).
The percentage of average biodegradation of the reference substance is more than 60%after 14 days of incubation (see Figure N. 2 and Attachment N. 2).


 


RESULTS
pH values have been reported in the table below.  





























































BottlepH value at T=0 Correction withpH value after correctionpH at the end of the test
Blank N.17.29////8.31
Blank N.27.31////8.22
Reference substance731////8.40
Test item N.17.42////8.45
Test item N.27.44////8.39
Reference substance + test item7.38////8.42
Abiotic check7.21////7.53

Inhibition check bottles results have shown that no inhibition effects have been caused by the test item; moreover, no abiotic degradation has occurred during the test.
The biodegradation percentage of the reference substance and the test item “REACTION MASS OF  MADECASSOSIDE















































CHECK POINT (Days)% OF BIODEGRADATION Reference substance% OF BIODEGRADATION Test item% OF BIODEGRADATION Reference substance + Test item
0000
14718
4591637
14786764
21836775
28836776

The trend of the biodegradation of the test item and the reference substance is reported in Figures N.1 and 2.


 


DEVIATIONS
No deviations have been detected during the study.



AND TERMINOLOSIDE”the during the test is detailed in the following table:

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
CONCLUSIONS
On the basis of results obtained, interpreted in accordance to OECD 301 F: 1992, the test item
“REACTION MASS OF MADECASSOSIDE AND TERMINOLOSIDE” should be considered readily
biodegradable in aerobic condition (10-day window was met).
Executive summary:

SUMMARY
The aim of this study is to determine the aerobic biodegradation of the test item “REACTION MASS OF MADECASSOSIDE AND TERMINOLOSIDE”, according to OECD 301 F: 1992.
The test has been done using the test item with a concentration of about 50 mg/L, giving about 100 mg ThODIL.
Sample has been kept at the temperature of 22°C + 2°C for the whole period of the test (28 days).
Evolved carbon dioxide has been absorbedin a solution of potassium hydroxide. The amount of oxygen taken up by the microbial population in the mud has been expressed as a percentage of Theoretical Oxygen Demand (ThOD).
On the base of results obtained, interpreted in accordance to OECD 301 F: 1992, the test item “REACTION MASS OF MADECASSOSIDE AND TERMINOLOSIDE”should be considered readily biodegradable in aerobic condition.

Description of key information

On the basis of results obtained, interpreted in accordance to OECD 301 F: 1992, the test item “REACTION MASS OF MADECASSOSIDE AND TERMINOLOSIDE” should be considered readily biodegradable in aerobic condition (10-day window was met).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

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