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Biodegradation in water: screening tests:

Various study for the test compound Hexylamine(CAS No. 111-26-2) and for its read across substance were reviewed for the biodegradation end point which are summarized as below:

Biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test substance Hexylamine by bacteria as a test inoculum (Takashi Kameya et. al; 1995). Two tests were carried out for studying the biodegradation of test substance Hexylamine. They are standard tests and low conc. tests. 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 and low conc. tests 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) in the standard test and by chromatography in low conc. test. 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 test compound was determined to be less than 30% in > 28 days in standard test and 100% degradation in 21 days in low conc. test, respectively. Thus, based on the percentage degradation, the test chemical was considered to be non-biodegradable in standard test and readily biodegradable in low conc. test.

Estimation Programs Interface Suite (EPI suite, 2016) was run to predict the biodegradation potential of the test compound Hexylamine (CAS no. 111- 26 -2) 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 Hexylamine is expected to be readily biodegradable.

28-days Manometric respirometry test following the OECD guideline 301Fto determine the ready biodegradability of the test item n-hexylamine (CAS No. 111-26-2) (UERL study report, Sustainability Support Services (Europe) AB, Report no. 111-26-2/01/2015/RBD, 2015). % Degradation was calculated using the values of BOD and ThOD for test item and reference item. The BOD28value of n-hexylamine (CAS No. 111-26-2) was observed to be 1.447mgO2/mg. ThOD was calculated as 2.846 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was found to be 50.84%.Based on the results, the test item, under the test conditions, was found to be inherently biodegradable at 20 ± 1°C over a period of 28 days.

Biodegradation study was conducted for > 28 days for evaluating the percentage biodegradability of test substance Hexylamine by anaerobic bacteria (Takashi Kameya et. al; 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 analyzing the decrease of DOC. The percentage degradation of the test compound was determined to be 50% in test 1 and 47% in > 28 days test 2, respectively. Thus, based on the percentage degradation, the test chemical was considered to be undergoe slow biodegradation under the given test conditions.

 

Biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of test substance n-butylamine (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l. The percentage degradation of test substance was determined to be 66% by BOD(NO2), 85% by BOD(NH3), 98% by TOC removal and 100% by HPLC in 14 days. Thus, the substance n-butylamine is considered to be readily biodegradable in water.

Biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test substance 1-Aminopropane (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 100 mg/l and initial test substance conc. used in the study was 30 mg/l. The percentage degradation of test substance was determined to be 49 and 85% by O2 consumption, BOD(NO2), 67 and 117% by O2 consumption , BOD(NH3), 88 and 100% by TOC removal and 100% by Test. mat. analysis, HPLC in 14 days. Thus, the substance 1-Aminopropane is considered to be readily biodegradable in water.

Biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of test substance Hexamethylene diamine (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l. The percentage degradation of test substance was determined to be 55.5% by BOD, 96.9% by TOC removal and 100% by GC in 14 days. Thus, the substance Hexamethylene diamine is considered to be readily biodegradable in water.

Biodegradation study was conducted for 21 days for evaluating the percentage biodegradability of test substance n-Amylamine (J-CHECK, 2016). Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l. The percentage degradation of test substance was determined to be 75% by BOD(NO2), 93% by BOD(NH3), 97% by TOC removal and 100% by HPLC in 21 days. Thus, the substance n-Amylamine is considered to be readily biodegradable in water.

The objectives of the test were to isolate a bacterial strain capable of degrading pentylamine and aniline and to define the optimal pentylamine and aniline degradation conditions for this bacterial strain. The bacterial strain was isolated from activated sludge obtained from a North eastern China treatment facility for petrochemical wastewater rich in pentylamine and aniline. Once the strain was isolated, five triplicate (5) batch tests were used to establish the conditions for maximum pentylamine degradation, by varying one at a time the following five factors: temperature, pH, reaction time, pollutant concentrations and aeration rate. In a final test, oil refinery sludge was inoculated with the strain and tested for the degradation of pentylamine under optimal conditions, while observing the degradation pathway of pentylamine. The isolated strain, PN1001, is a member of the Pseudomonas species and it was capable of degrading pentylamine. The optimal reactor conditions for the degradation of a mixture of pentylamine, at a concentration ranging between 150 and 200 mg/L, were found to be 30°C at a pH of 7.0, under a reaction time of 24 h and a maximum solution dissolved oxygen level of 6 mgO2/L. Under such conditions, the strain PN1001 degraded 93% of the pentylamine. Once inoculated with the strain, oil refinery sludge degraded 93% of the pentylamine, compared to the strain alone which degraded 72% likely because of the sludge’s buffering effect against the toxic environment.

Although 1 supporting data i.e, experimental study of the target substance Hexylamine, indicates that the test chemical is inherently biodegradable in nature, but the key study which is from a k2 level publication and other supporting data for target and read across substance indicate that the substance Hexylamine is readily biodegradable in nature. Thus, based on the overall results for target and read across substance, it can be concluded that the test substance, Hexylamine can be expected to be readily biodegradable in nature.

Biodegradation in water and sediment: simulation tests

Estimation Programs Interface (EPI) Suite (2016) prediction model was run to predict the half-life in water and sediment for the test compound Hexylamine (CAS No. 111-26-2). If released in to the environment, 28.3 % of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period ofHexylaminein water is estimated to be 8.666 days (208 hrs) whereas the half-life period of Hexylamine in sediment is estimated to be 77.91 days (1870 hrs). These values indicate that Hexylamine is not persistent in nature.

Biodegradation in soil

Various study and predicted data for the test compound Hexylamine(CAS No. 111-26-2) were reviewed for the biodegradation end point which are summarized as below:

The half-life period ofHexylamine(CAS No. 111-26-2) 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, 70.3% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period ofHexylaminein soil is estimated to be 17.33 days(416 hrs).Based on this half-life value ofHexylamine, 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. 

The study was carried out to determine the effects of microbial utilization of sorbed amines and to establish whether the rate of biodegradation of a sorbed substrate is equal to its rate of desorption (WSZOLEK, P.C; ALEXANDER, M., 1979). The incubation time was 0.3 and 0.42 days. The inoculum was a mixed culture of bacteria grown on the individual amines as sole carbon source to give an initial level of about 106cells/ml. The original source of the organisms was Lima Loam. The tests were carried under aerobic conditions at a pH of 7.2 and concentration of 71 and 63 ppm at 30°C and 22°C. The rate of biodegradation of n-hexylamine under aerobic conditions is 100%. It can be conducted that n-hexylamine biodegrades fast with acclimation.

On the basis of above results for target substance, it can be concluded that the test substance Hexylaminecan be considered to be not persistent in the soil environment

On the basis of available information, the test substance Hexylamine can be considered to be readily biodegradable in nature