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Biodegradation in water

On the basis of the experimental studies of the read across chemical and applying the weight of evidence approach, the percentage degradation the test chemical can be expected to be > 90.9% to < 92.02% and 98.8% using O2 consumption and DOC removal parameter in 28 days. Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.

Additional information

Biodegradation in water

Data available of the structurally and functionally similar read across chemicals has been reviewed to determine the percentage biodegradability of the test chemical. The studies are as mentioned below:

 

Biodegradation study was conducted for 28-days following the OECD guideline 301 D for determining the ready biodegradability of the test chemical. The study was performed at a temperature of 20°C. The test system included control, test chemical and reference substance. Polyseed were used as a test inoculum for the study. The concentration of test and reference substance (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l. OECD mineral medium was used for the study. ThOD (Theoretical oxygen demand) of test and reference chemical was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test chemical and reference substance. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 79.51%. Degradation of Sodium Benzoate exceeds 54.21% on 7 days & 75.3% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 0.9 mgO2/mg. ThOD was calculated as 0.99 mgO2/mg. Accordingly, the % degradation of the test chemical after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 90.9%. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable in nature.

 

Another 28-days Closed Bottle test following the OECD guideline 301 D was conducted for determining the ready biodegradability of the test chemical. The study was performed at a temperature of 20°C and using the same test procedure as mentioned in the above study. The % degradation of procedure control (reference substance) was also calculated using BOD & ThOD and was determined to be 85.54%. Degradation of Sodium Benzoate exceeds 67.46% on 7 days & 73.49% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.The BOD28 value of test chemical was observed to be 1.27 mgO2/mg. ThOD was calculated as 1.38 mgO2/mg. Accordingly, the % degradation of the test chemical after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 92.02%. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable in nature.

 

For the test chemical, biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test chemical. The study was performed following the OECD Guideline 302 B "Inherent biodegradability: Modified Zahn–Wellens Test" under aerobic conditions. Activated sludge (non-adapted) obtained from a domestic sewage treatment plant at the ARA Basel Industry was used as a test inoculum. Conc. of inoculum and initial test chemical conc. used were 1000 mg/l and 150 mg/l (based on DOC). Test medium was prepared according to the specification of the EEC L133 (pp. 99-105), volume 31 resp. OECD Method 302B. Test was performed in duplicates under indirect daylight condition at 22±3°C. A Shimadzu TOC-500 analyzer was used to determine the TOC. The degradation of test chemical at time t was calculated from the DOC values. Diethylene glycol (158.3 mg/l related to DOC) was used as a reference substance which undergoes degradation at 5, 7, 9 and 21 days with a percentage degradation of 10.2%, 49.5%, 96.7% and 98.8%, respectively. The percentage degradation of test chemical was determined to be 98.8% by using DOC removal parameter in 28 days. Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.

 

On the basis of the experimental studies of the read across chemical and applying the weight of evidence approach, the percentage degradation the test chemical can be expected to be > 90.9% to < 92.02% and 98.8% using O2 consumption and DOC removal parameter in 28 days.  Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.