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Biodegradation in water

Biodegradability of test chemical 7-[[2-[(aminocarbonyl)amino]-4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]phenyl]azo]naphthalene-1,3,6-trisulphonic acid (CAS No. 35642 -64 -9) is predicted using OECD QSAR tool box v.3.3 (2017) using log Kow as primary descriptor. The test chemical 7-[[2-[(aminocarbonyl)ami no]- 4-[(4-amino-6-chloro-1,3,5-triazin-2 -yl)amino]phenyl]azo]naphthalene-1,3,6-trisulphonic acid undergoes 0.8571 % biodegradation by considering BOD as parameter and microorganisms as inoculum in 28 days. On the basis value of percent biodegradability this chemical is considered as not readily biodegradable.

Additional information

Biodegradation in water

Various predicted data for the target chemical 7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acid(CAS No. 35642-64-9) and supporting weight of evidence studies for its functionally similar read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2017) using OECD QSAR toolbox version 3.3 with logKow as the primary descriptor, percentage biodegradability of test chemical7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acid(CAS No. 35642-64-9) was estimated.Test substance undergoes 0.86% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acidwas estimated to be not readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2018), the biodegradation potential of the test compound7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acid(CAS No. 35642-64-9) in the presence of mixed populations of environmental microorganisms was estimated.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 chemical7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acidis expected to be not readily biodegradable.

 

In a supporting weight of evidence study from study report (Sustainability Support Services (Europe) AB, Report no. 4548-53-2/01/2016/RBD, 2016) for the read across chemical Disodium 3-[(2,4-dimethyl-5-sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate (CAS no. 4548-53-2), 28-days Manometric respirometry testfollowing the OECD guideline 301F to determine the ready biodegradability of the read across item disodium 3- [(2,4 -dimethyl-5 -sulphonatophenyl)azo]-4 -hydroxynaphthalene-1 -sulphonate. 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 10 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 BOD28 value of disodium 3-[(2,4-dimethyl-5- sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate, CAS No. 4548-53-2 was observed to be mgO2sup>/mg. ThOD was calculated as mgO2/mg. Accordingly, the % degradation of the read across item Disodium 3-[(2,4-dimethyl-5-sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 12.807 %.Based on the results, the test item, under the test conditions, was considered to be not readily biodegradable at 20± 1°C over a period of 28 days.

 

Another biodegradation study of 28-days Closed Bottle test following the OECD guideline 301D was conducted for determining the ready biodegradability of the read across item disodium 3 -[(2,4 -dimethyl-5 -sulphonatophenyl)azo]-4 -hydroxynaphthalene-1 –sulphonate (CAS no. 4548-53-2) (Sustainability Support Services (Europe) AB, Report no. 4548-53-2/01/2016/CBT, 2017). The test system included control, test item and reference item. The concentration of test and reference item (Sodium Benzoate) chosen for the study was 32 mg/l and 32mg/l, while that of inoculum was 32ml/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 BOD 28value of Disodium 3 -[(2,4 -dimethyl-5 -sulphonatophenyl)azo]-4 -hydroxynaphthalene-1 –sulphonate was observed to be 0.475 mgO2/mg. ThOD was calculated as 1.465 mgO2/mg. Accordingly, the % degradation of the read across item Disodium 3-[(2,4-dimethyl-5-sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 32.42%. Based on the results, the test item disodium3 -[(2,4 -dimethyl-5 -sulphonatophenyl)azo]-4 -hydroxynaphthalene-1 -sulphonate, under the test conditions, was considered to be not readily biodegradable at 20 ± 1°C over a period of 28 days.

 

For the read across chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt (CAS no. 2611-82-7) from authoritative database (J-CHECK, 2017), the chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was subjected to biodegradation test by taking sludge as inoculums at 30 mg/L concentration. The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) and other guideline “Biodegradation test of a chemical substance using a microorganism etc. provided in the Notice on the Test Method Concerning New Chemical Substances", respectively. Biodegradation was analysed by using O2 Consumption, TOC removal and test material analysis by HPLC parameters. The initial concentration of test chemical was 100 mg/L. After 4 weeks (28 days) test chemical 1,3-Naphthalenedisulfon ic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt showed 2% biodegradability by O2 consumption and TOC removal parameter and 0 % biodegradation by test material analysis by HPLC parameter so it is concluded that test chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo -1-naphthalenyl)azo)-, trisodium salt is not readily biodegradable.

 

Another biodegradation study was conducted for evaluating the percentage biodegradability of read across substance 1,3 -Naphthalenedisulfonic acid, 7 -hydroxy-8 -((4 -sulfo-1 -naphthalenyl)azo)-, trisodium salt (CAS no. 2611 -82 -7) (Toshihide Saito, et. al; 1984). Activated sludge was used as a test inoculum obtained from municipal sewage. Test substance of conc. 500 mg/l was prepared and diluted as needed. The COD measurement was performed by the potassium dichromate reflux method based on Japanese Industrial Standards. In the BOD measurement, a sample solution was taken into a container. Then JIS-BOD testing solutions, i.e. 3 ml of A solution and 1 ml of B, C, D solutions were added to the sample solution, respectively. Then 5 ml of the supernatant of the municipal sewage activated sludge was added to the sample solution and diluted to 300 ml with water. Immediately, the BOD-time curve was recorded at 20~ using an Ohkura OM-200I type coulometer. The TOC measurement was carried out by a Yanagimoto TOC-ILW.BOD5, COD, ThOD and TOC value of the test chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was determined to be 0.021, 0.65, 1.23 and 0.20 g/g, respectively. The BOD5/TOC ratio of chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was determined to be 0.11 (i.e. ranges in between 0.08-0.89), indicating that the chemical is highly resistant to aerobic biodegradation. Thus, based on this value BOD5/TOC value, it can be concluded that the chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt is not readily biodegradable in nature.

 

Additional biodegradation study from peer reviewed journal (U. Pagga and O. Brown, 1986) was carried out for 48 days for evaluating the percentage biodegradation of the read across chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt (CAS no. 2611-82-7) using modified OECD Guideline 302B. Activated sludge was used as a test inoculum. The sources of the activated sludge were treatment plants conveniently located to the laboratories carrying out the test. These treatment plants received communal and/or industrial wastewater. Concentration of inoculum i.e, activated sludge used was 0.5 g/l and initial test substance conc. used in the study was 100 mg/l. Analytical methods involve the measurement of extinction at absorption maximum 412 nm and DOC (dissolved organic carbon).The percentage degradation of substance 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was determined to be 5% by DOC removal. Based on the limit values for classification of Static Test – the test chemical was classified in CATEGORY ‘D’. Thus, the substance 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt is considered to be not readily biodegradable in nature.

 

In a supporting weight of evidence study from peer reviewed journal (Yasuhide TONOGAI et. al, 1978) for read across substancetrisodium (4E)-3-oxo-4-[2-(4-sulfonatonaphthalen-1-yl)hydrazin-1-ylidene]-3,4-dihydronaphthalene-2,7-disulfonate (CAS no. 915-67-3),biodegradation study was conducted under aerobic conditions for evaluating the percentage biodegradability of read across substance trisodium (4E)-3-oxo-4-[2-(4-sulfonatonaphthalen-1-yl)hydrazin-1-ylidene]-3,4-dihydronaphthalene-2,7-disulfonate. Activated sludge was used as a test inoculum obtained from the municipal sewage treatment plant, Nakahama, Osaka. The return sludge was acclimated to the synthetic sewage for a week or longer, and it was used for the aerobic and anaerobic decomposition experiments. Synthetic sewage was prepared by dissolving Glucose, peptone and potassium dihydrogen phosphate, 30g each, in 1 liter water and the pH was adjusted to pH 7.0 with sodium hydroxide. Concentration of inoculum used for the study was3000 mg/l. Percentage degradation of chemical was determined by measuring the absorbance (test material analysis), oxygen uptake and BOD parameter. For the aerobic decomposition of dyes with sludge, 250 ml of O.03 M dye solution was added to 750ml of sludge (MLSS ca, 3,000 ppm), and bubbled with air sufficiently at 20°C. 5ml sample was taken out once a day. After sampling 5ml of synthetic sewage was added to the mixture. Each sample was filtered through filter paper and diluted twenty times prior to the spectrophotometric measurement at the absorption maximum within the visible range. The decrease of dyes concentration was expressed in terms of percent to the initial absorption whereas measurement oxygen uptake by sludge involve 2.0 ml of sludge, 0.2 ml of 1,000 ppm dye solution, and O.2 ml of 20% potassium hydroxide were pipetted into the vessel, the side arm and central well, respectively. The sludge and the dye solution were mixed and the vessel was shaken at 25"C. The oxygen uptake was measured. The oxygen uptake by sludge alone was subtracted from the dye addition. For determining the BOD values, test chemical solutions (10, 20 and 40 ppm) were prepared with the seeded dilution water and kept at 20°C. The dissolved oxygen contents were then measured by using a dissolved oxygen meter. The percentage degradation of test chemicaltrisodium (4E)-3-oxo-4-[2-(4-sulfonatonaphthalen-1-yl)hydrazin-1-ylidene]-3,4-dihydronaphthalene-2,7-disulfonatewas determined to be 20% in 10 days by using the test material analysis parameter. From the oxygen uptake by Warburg’s manometer, the low activity of the sludge to dye was obtained and by using the dissolved oxygen meter, the dissolved oxygen contents on the 5th day were essentially the same to initial ones. Thus, based on percentage degradation, the chemical trisodium (4E)-3-oxo-4-[2-(4-sulfonatonaphthalen-1-yl)hydrazin-1-ylidene]-3,4-dihydronaphthalene-2,7-disulfonate was considered to be not readily biodegradable in nature.

 

On the basis of above results for target chemical 7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acid (from OECD QSAR toolbox version 3.3, 2017 and EPI suite, 2018) and for its read across substance (from UERL study reports,peer reviewed journals,authoritative database J-CHECK), it can be concluded that the test substance 7-[(E)-2-{4-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-(carbamoylamino)phenyl}diazen-1-yl]naphthalene-1,3,6-trisulfonic acid can be expected to be not readily biodegradable in nature.