Sodium hydrogen-5-sulphoisophthalate

Biodegradation in water: screening tests

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:

12 July 1996 to 9 October 1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

and EEC/Annex V C.4

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Activated sludge was obtained from the Van Lare Treatment Plant (domestic), Rochester, NY (USA). Upon arrival at the testing laboratory the sludge was aerated for about 4 hours. A sample (about 2000 ml) was collected and homogenized for 2 minutes with a mechanical blender. After settling for 1 hour, the supernatant was pipetted to provide sufficient volume for a 1% inoculum for each test carboy. Viability of the supernatant microorganisms was confimed by using an Easicult TTC dip slide to estimate microbe numbers.

Duration of test (contact time):

28 d

Initial conc.:

55.8 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: A basal salts medium prepared in distilled water.
- Test temperature: 21 - 22 deg C during the test period
- pH: The pH of basal salts medium and the positive control stock solution was measured at test start. pH was not adjusted. The pH was measured in test carboys on day 27 before addition of HCl.
- Aeration of dilution water: Air (50 to 100 ml/min, with CO2 removed) was passed throuigh inoculated test carboys for 24 hours to purge the system of carbon dioxide. During the study, each carboy was agitated with a magnetic stir bar and aerated with CO2-free air at 50 to 100 ml/min.
- Other: A dissolved organic carbon analysis was performed at the start of the studies and on the final day 28.

TEST SYSTEM
- Method used to create aerobic conditions: Continuous purging with carbon dioxide-free air at 50 to 100 ml/min.
- Details of trap for CO2 and volatile organics if used: Each test carboy was equiped with 3 CO2 absorber bottles connected in series each containing 100 ml of 0.0125 M barium hydroxide.

SAMPLING
- Sampling frequency: Titrations of barium hydroxide trapping solutions as deemed necessary for the first 10 days and twice a week until day 27. Titrations were performed before and after addition of acid to test carboys on the 27th day.
- Sampling method: Barium hydroxide (100 ml) was removed and titrated.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Two test carboys served as inoculum blanks.
- Abiotic sterile control: Not used.
- Toxicity control: Not used


STATISTICAL METHODS:
Results were reported as average values for replicate analyses.

Reference substance:

benzoic acid, sodium salt

Remarks:

CAS No. 000532-32-1, purity 99.7%

Parameter:

% degradation (CO2 evolution)

Value:

2

Sampling time:

28 d

Details on results:

Total cumulative degradation in both test vessels reached 2% by the end of the study. The dissolved organic carbon (DOC) increased in the Test #1 carboy from 15.3835 to 18.0378 mg/L (17.2%) and in Test #2 carboy from 15.5435 to 18.1018 mg/L (16.5%).

Results with reference substance:

The positive control sodium benzoate yielded 77% of the theoretical carbon dioxide evolution over the course of the study. The dissolved organic content of the positive control fell from 20.22 to 0.57 mg/l over the test period. No significant amount of carbon dioxide evolution (<40 mg/l) was evolved from the inoculum blank.

Conclusions:

These results indicate that the test substance is not readily biodegradable under the conditions of this study.

Description of key information

The determination of Ready Biodegradability (Biotic Degradation) using The CO2 Evolution Test (Modified Sturm OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test) was identified as the key study.  Only 2% biodegradation was observed after 28 days.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

In a key study conducted according to OECD Guideline 301B (Ready Biodegradability: CO2 Evolution Test), only 2% biodegradation was recorded in 28 days. In a supporting study, the measured biochemical oxygen demand according to a method referencing, "Determination of Biochemical Oxygen Demand" method of the US EPA, Method 405, 1979 and the "Degradation, Biochemical Oxygen Demand", Method C.5, EC, 1992. The 5-day BOD value was found to be less than 0.00038 g of oxygen per g of test substance. The 20-day BOD value was found to be 0.0011 g of oxygen per g of test substance at a 0.090 percent concentration. The BOD/COD ratio was found to be less than 0.00047. The COD was found to be 0.808 g/g of test substance. Based on these two studies the substance is found not to biodegrade.