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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:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Justification for type of information:
Data is from handbook
Qualifier:
according to
Guideline:
other: as mentioned below
Principles of method if other than guideline:
Biodegradation study was conducted for evaluating the percentage biodegradability of test chemical.
GLP compliance:
not specified
Oxygen conditions:
not specified
Inoculum or test system:
other: Nocardia spp.
Based on:
not specified
Parameter followed for biodegradation estimation:
not specified
Key result
Parameter:
other: Biodegradation
Remarks on result:
other: Although %degradation of test chemical was not known, but chemical was reported to be degradable by Nocardia sp. in wastewaters.
Validity criteria fulfilled:
not specified
Interpretation of results:
other: biodegradable
Conclusions:
Although % degradation of test chemical was not known, but chemical was reported to be degraded by Nocardia sp. in wastewaters. Thus, based on this, test chemical was considered to be biodegradable in water.
Executive summary:

Biodegradation study was conducted for evaluating the percentage biodegradability of test chemical. Although % degradation of test chemical was not known, but chemical was reported to be degraded by Nocardia sp. in wastewaters. Thus, on the basis of the results reported, test chemical was considered to be biodegradable in nature.

Description of key information

Biodegradation study was conducted for evaluating the percentage biodegradability of test chemical. Although % degradation of test chemical was not known, but chemical was reported to be degraded by Nocardia sp. in wastewaters. Thus, on the basis of the results reported, test chemical was considered to be biodegradable in nature.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Summarized result for the determination of biodegradation rate of test chemical and structurally and functionally similar read across chemicals were reviewed and mention as below:

Biodegradation study was conducted for evaluating the percentage biodegradability of test chemical. Although % degradation of test chemical was not known, but chemical was reported to be degraded by Nocardia sp. in wastewaters. Thus, on the basis of the results reported, test chemical was considered to be biodegradable in nature.

Above study further supported by the second weight of evidence study from experimental report. 28-days Manometric respirometry test was conducted following the OECD guideline 301F to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 30 mg/L, while that of inoculum was 25 ml/l. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was determined to be 70.27%. The mean BOD values (mg O2/l) in control on 28th day was 16.31 mg O2/l, thereby fulfilling the control validity criteria (i.e., the oxygen consumption of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium Benzoate exceeds 56.056 %after 7 days and 61.461 % after 14 days. The activity of the inoculums is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 2.013 mgO2sup>/mg. ThOD was calculated as 2.262 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 89.007 %. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable at 20 ± 1°C over a period of 28 days.

Similar 14-days Closed Bottle test was conducted following the OECD guideline 301 D to determine 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 item. Polyseed were used for this study. 1 polyseed capsule were added in 500 ml D.I water and then stirred for 1 hour for proper mixing and functioning of inoculum. This gave the bacterial count as 10E7 to 10E8 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. The concentration of test and reference chemical (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 item was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test chemical and reference chemical. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 75.3 % at 20 ± 1°C. Degradation of Sodium Benzoate exceeds 64.46% on 7 days & 75.30% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid.The BOD14 value of test chemical was observed to be 1.47 mgO2/mg. ThOD was calculated as 2.31 mgO2/mg. Accordingly, the % degradation of the test chemical after 14 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 63.63 %. Based on the results, the test chemical was considered to be readily biodegradable in water.

Thus, based on the above all studies and rate of degradation observations, chemical was considered to be readily biodegradable in nature.