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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:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Qualifier:
according to guideline
Guideline:
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Test Item
Designation in Test Facility: 17042002G
Date of Receipt: 20. Apr. 2017
Condition at Receipt: Room temperature, in proper conditions

Specification
Name sodium 3-sulfobenzoate
Batch no. 170103
Appearance White crystalline powder
Composition sodium 3-sulfobenzoate
CAS No. 17625-03-5
EINECS-No. 241-602-5
Molecular formula C7H5SO5Na
Molecular weight 224.17 g/mol
Purity > 99.0% (Titration with NaOH, Glass indicating electrode, Calomel reference electrode)
Homogeneity totally homogeneous
Volatility not available
Stability H2O: 96h; EtOH: unknown; acetone: unknown; CH3CN: unknown; DMSO: unknown
Solubility H2O: >1 g/l; EtOH: unknown; acetone: unknown; CH3CN: unknown; DMSO: unknown
Production date 2017
Expiry date January 2019
Storage Room Temperature (20 ± 5°C), keep away from humidity

Safety Precautions
For handling, information given in the MSDS will be observed.

Storage
The test item is stored in a closed vessel at room temperature (20 ± 5°C),protected from humidity.

Pre-Treatment
A stock solution containing 1 g/L ± 10 % test item was prepared and its DOC was measured in order to determine the volume to be added to the test vessels.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Activated sludge was used as inoculum (concentration in the test 25.1 mg dry matter/L).
Duration of test (contact time):
28 d
Initial conc.:
40 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
Preparations
The medium was prepared using the stock solutions. The inoculum was taken from its source, washed, aerated and the dry matter was determined. The stock solutions of the positive control and the test item were prepared and their DOC content was measured.

Experimental Parameters
Flask volume 250 mL
Controls 2, containing mineral medium and inoculum
Positive control flasks 2, containing positive control, mineral medium and inoculum
Test flasks 2, containing test item, mineral medium and inoculum
Abiotic control 1, containing test item, mineral medium and HgCl2
Adsorption control 1, containing test item, mineral medium, inoculum and HgCl2
Toxicity control 1, containing test item, positive control, mineral medium and inoculum
Inoculum concentration 25.1 mg/L
Temperature 20.1 – 21.3 °C
Duration 28 days

The test was performed with a start concentration of 40.0 mg organic carbon/L of test item and 39.9 mg organic carbon/L of positive control. The pH of each flask was measured and adjusted within a range of 7.3 – 7.4.

Determination of Dissolved Organic Carbon
From each replicate, 7 samples were taken in order to determine the DOC (after 3 hours and on days 4; 8; 11; 14; 21 and 28). The sample volume was 2 mL. The samples were filtrated and the DOC-concentrations were measured. DOC was determined as difference between TC (total carbon) and IC (inorganic carbon) using the carbon analyser TOC multi N/C 2100S, Analytik Jena. Each filtrated sample was measured at least in duplicate. The carbon analyser was calibrated with freshly prepared reference solutions (C8H5KO4 for TC, Na2CO3 and NaHCO3 for IC) once per month. A QC-sample was measured daily. All values were documented in the raw data.
Reference substance:
other: potassium hydrogenphthalate for TC, Na2CO3 and NaHCO3 for IC
Parameter:
% degradation (DOC removal)
Value:
3.1
Sampling time:
4 d
Parameter:
% degradation (DOC removal)
Value:
79.7
Sampling time:
8 d
Parameter:
% degradation (DOC removal)
Value:
83.5
Sampling time:
11 d
Parameter:
% degradation (DOC removal)
Value:
84.3
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
87.4
Sampling time:
21 d
Parameter:
% degradation (DOC removal)
Value:
88
Sampling time:
28 d
Details on results:
Results
- The 10-day-window began on day 4, at its end, 84 % were reached, surpassing the pass level of 70% stated in the OECD Guideline.
- The degree of biodegradation reached 88 % after 28 days.
- The test item can be considered as "readily biodegradable".

Validity
- The difference within replicates at the end of the test was 1.1 % (criterion: ≤ 20%).
- The positive control reached the pass level of 70 % on day 4 (criterion: > 70% within 14 days).
- The total biodegradation in the toxicity control after 14 days was 90 % (criterion: > 35 %).

Discussion
The validity criteria were met. No observations showing inconsistencies of the test data were made. Degradation behaviour of positive control and toxicity control was normal. Abiotic degradation was not observed. Both replicates of the test item showed very good correspondence. Ready degradability is defined in the guidelines as degradation surpassing 70% within 10 days after reaching a level of 10 %. Therefore, the test item sodium 3-sulfobenzoate can be considered as "readily biodegradable".
If degradation in the toxicity flask is below 35 % after 14 days, the test item can be considered as toxic towards the inoculum. As degradation in the toxicity flask was 90 % after 14 days, the test item can be stated as "not toxic" towards the inoculum in a concentration of 106.3 mg/L.
The result of the test can be considered valid.

The calculated values for the percentage degradation are presented in the following table.

 Day Positive Control 1  Positive Control 2  Positive Control Mean  Test 1  Test 2  Test Mean  Abiotic control  Adsorption Control  Toxicity Control 
 4 97.7  99.1  98.4  2.7  3.5  3.1  2.5  - 1.8  49.1 
 8 96.8  96.6  96.7  80.6  78.8  79.7  5.3  3.2  88.5 
 11 96.9  97.3  97.1  83.3  83.6  83.5  - 0.2  - 1.8  88.9 
 14 98.0  97.7  97.9  84.1  84.5  84.3  2.1  - 2.3  89.7 
 21 98.5 98.5  98.5  87.0  87.7  87.4  4.2  - 1.6  90.7 
 28 99.1  99.2  99.2  87.4  88.5 88.0  - 3.4  - 7.8  91.4 
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item sodium 3-sulfobenzoate can be considered as "readily biodegradable".
Executive summary:

The determination of the aerobic ready biodegradability of sodium 3-sulfobenzoate in the DOC die-away test has been performed following the OECD Guideline 301A and EU C.4-A.

The 10-day-window began on day 4, at its end, 84 % were reached, surpassing the pass level of 70% stated in the OECD Guideline. The degree of biodegradation reached is of 88 % after 28 days; therefore, the test item can be considered as "readily biodegradable".

Description of key information

The determination of the aerobic ready biodegradability of sodium 3-sulfobenzoate in the DOC die-away test has been performed following the OECD Guideline 301A and EU C.4-A.

The 10-day-window began on day 4, at its end, 84 % were reached, surpassing the pass level of 70% stated in the OECD Guideline. The degree of biodegradation reached is 88 % after 28 days; therefore, the test item can be considered as "readily biodegradable".

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

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