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Biodegradation in water: screening tests:

Various predicted data for the test compound3'-Hydroxyacetophenone(CAS No. 121-71-1) and for its read across substance were reviewed for the biodegradation end point which are summarized as below:

Estimation Programs Interface Suite (EPI suite, 2016) was run to predict the biodegradation potential of the test compound 3'-Hydroxyacetophenone (CAS no. 121 -71 -1) in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI LInear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that 3'-Hydroxyacetophenone is expected to be readily biodegradable.

Biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of read across substance 4-Hydroxybenzoic acid (CAS no. 99-96-7) (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial substance conc. used in the study was 100 mg/l. The percentage degradation of read across substance was determined to be 90% by BOD and 100% by both TOC removal and HPLC in 14 days. Thus, based on percentage degradation, 4 -Hydroxybenzoic acid was considered to be readily biodegradable in nature.

Biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of read across substance Phenol (CAS no. 108-95-2) (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial substance conc. used in the study was 100 mg/l. The percentage degradation of read across substance was determined to be 85% by BOD, 95% by TOC removal and 100% by UV-Vis in 14 days. Thus, based on percentage degradation, Phenol was considered to be readily biodegradable in nature.

Biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of read across 3-Ethylphenol (CAS no. 620-17-7) (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial substance conc. used in the study was 100 mg/l. The percentage degradation of read across substance was determined to be 92% by BOD, 98%by TOC removal and 100% by HPLC in 28 days. Thus, based percentage degradation, 3-Ethylphenol was considered to be readily biodegradable in nature.

Biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of read across substance Salicylic acid (CAS no. 69-72-7) (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial substance conc. used in the study was 100 mg/l. The percentage degradation of read across substance was determined to be 88.1% by BOD, 97.6% by TOC removal and 100% by both UV-Vis and HPLC in 14 days. Thus, based on percentage degradation, Salicylic acid was considered to be readily biodegradable in nature.

Biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of read across substance Phenol (CAS no. 108-95-2) by bacteria as a test inoculum (Takashi Kameya et. al; 1995). Seeding bacteria was used as a test inoculum. The seeding bacteria had been cultured in a continuous anaerobic bioreactor at 37 + 1°C.Synthetic sewage, composed of glucose, peptone and corn steap liquor (carbon ratio = 1:1:2), is supplied into the reactor (3.0 g-C/l, 8.0 g-CS./.d). In this culture, > 95% acidic decomposition and > 90% methanogenic decomposition are achieved.

A standard test using 50 ml vials (total capacity: 68 ml) was employed. Ten test vials were prepared under the same conditions, and they were set in a water bath at 37°C ± 0.5”C. The original solution was added to the test inoculum and organic medium in oxygen-free water. At the starting time and after every week, two vials were opened simultaneously, and the concentration of organic compound was analyzed. The concentration of organic compound was determined by dissolved organic carbon (DOC).Biodegradation ratio is determined by analysing the decrease of DOC in the standard test. Reproducibility is confirmed by the biodegradation ratio of benzoic acid being > 78% after 14 days.

The percentage degradation of the read across compound was determined to be less than 96% in 21 days in standard test Thus, based on the percentage degradation, the read across chemical Phenol was considered to be readily biodegradable in nature.

 

Biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of read across substance Phenol (CAS no. 108-95-2) by anaerobic bacteria as a test inoculum (The Science of the Total Environment, Vol. 170, Pg. no. 31-41, 1995) . Two test were carried out by using different conc. of test chemical and inoculum. Anaerobic bacteria was used as a test inoculum. The cultivated bacteria was prepared for seeding as follows. The bacteria suspension was drowned, homogenized, and separated with a centrifuge at 3000 rev./min for 10 min. The deposit was washed by the basal medium solution and separated again with a centrifuge. The deposit was dissolved again in the basal medium solution and its concentration was determined. This original suspension of bacteria was seeded in the test vials and its concentration was reconfirmed. The seeding bacteria had been cultured by a synthetic sewage in a continuous bioreactor at 37 + 1°C. 100 and 30 mg/l conc. was used for both inoculum and test substance conc., respectively.

The test involve the use of 50 ml vials (total capacity: 68 ml). Ten test vials were prepared under the same conditions, and they were set in a water bath at 37°C ± 0.5”C. The original solution was added to the test inoculum and basal medium solution, which was prepared by organic medium and/or inorganic medium in oxygen-free water. At the starting time and after every week, two vials were opened simultaneously, and the concentration of organic compound was analyzed. The concentration of organic compound was determined by dissolved organic carbon (DOC) or chromatography. Biodegradation ratio is determined by analyzisng the decrease of DOC. The percentage degradation of the read across compound was determined to be 60% in test 1 and 55% in 7 days in test 2, respectively. Thus, based on the percentage degradation, the read across chemical Phenol was considered to be readily biodegradable under the given test conditions.

 

On the basis of above results for target and read across substance, it can be concluded that the test substance 3'-Hydroxyacetophenone can be expected to be readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (EPI) Suite (2016) prediction model was run to predict the half-life in water and sediment for the test compound 3'-Hydroxyacetophenone (CAS No. 121 -71 -1). If released in to the environment, 20.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 3'-Hydroxyacetophenone in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 3'-Hydroxyacetophenone in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.0949%), indicates that 3'-Hydroxyacetophenone is not persistent in nature.

Biodegradation in soil

The half-life period of 3'-Hydroxyacetophenone (CAS No. 121 -71 -1) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2016). If released into the environment, 79% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 3'-Hydroxyacetophenone in soil is estimated to be 30 days (720 hrs). Based on this half-life value of 3'-Hydroxyacetophenone, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

On the basis of available information, the test substance 3'-Hydroxyacetophenone can be considered to be readily biodegradable in nature.