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Biodegradation in water: screening tests

A number of studies for the test compound 2-nitro-p-phenylenediamine (CAS No. 5307-14-2) alongwith its predicted data andread across substance studies were reviewed for the biodegradation end point which are summarized as below:

Biodegradation in water ability was predicted for the test compound 2-nitro-p-phenylenediamine (CAS No. 5307-14-2) using the SSS QSAR prediction model. The ready biodegradability of the test substance2-nitro-p-phenylenediaminewas estimated as 3% by using BOD parameter. This result indicates that2-nitro-p-phenylenediaminewas estimated to be not readily biodegradable in water.

 

Estimation Programs Interface Suite (EPI suite) was run to predict the biodegradation potential of the test compound2-nitro-p-phenylenediamine (CAS No. 5307-14-2). The screening test inherent to the biodegradability of the substance was calculated using the software BIOWIN v4.10. The results indicate2-nitro-p-phenylenediaminewas estimated to be not readily biodegradable in water.

 

Biodegradation screening test (J-CHECK, 2016) on read across substance was conducted for 14 days (2 weeks) for evaluating the percentage biodegradability of the test substance. Concentration of inoculum i.e, sludge is 30 mg/l and initial test substance conc. used in the study is 100 mg/l. The percentage degradation of test substance was found to be 0% by BOD and 2.9% by TOC. Thus, the substance 4 -nitroaniline was considered to be not readily biodegradable in water.

 

Biodegradation test (P. Pitter, 1976) on read across substancewas conducted for 20 days for evaluating the percentage biodegradability of the test substance 4-nitroaniline.

 

Activated sludge was used as a test inoculum.

 

Activated sludge taken from a sewage plant is cultivated in a 1000ml volumetric cylinder. The mixture is aerated with pressure air. Every day 200 ml of the mixture is driven off so that the sludge age is 5 days. After driving off the 200ml of the mixture aeration is interrupted, and after sedimentationca. 600mlof the liquid phase is driven off. The residue (200 ml of the thickened activated sludge) is diluted with tap water to the volume ofca.800 ml and 600 mg/l of starch or glucose, 600 mg/l of peptone, 25 ml of a phosphate buffer pH 7.2, and the solution of the tested compound are added. Then the mixture in the cylinder is made up to 1000ml with tap water and aerated for 23 h (the recirculation ratio is 0-25). After this period the procedure is repeated.

 

The tested substance is dissolved in a beaker in a biological medium in a concentration corresponding to 200mg 1 -I COD. To the biological medium such amount of thickened adapted activated sludge is added to make dry matter of the inoculum 100mgl. The beaker is placed in a dark room with a roughly 3 constant temperature of 20 ± 3 °C on an electromagnetic stirrer. The initial value of COD or organic carbon of the liquid phase are determined.

 

Samples were filtered or centrifuged before analysis, are taken at suitable intervals. The decrease of the tested substance in the liquid phase is evaluated by determining COD or organic carbon. With the degree of degradation also the average specific rate of degradation is determined, expressed in terms of mg COD (or organic carbon) removed by a gramme of dry matter of the activated sludge per hour.

 

The experiment is carried out till there is no decrease of COD. After that time the total percentage of COD removed and the rate of degradation are evaluated. Conc of test substance used for the study was 200mg/l, respectively.

 

The substance p-nitroaniline was considered to be not readily biodegradable in water.

 

Biodegradation screening test (J-CHECK, 2016) on another read across substance was conducted for 28 days (4 weeks) for evaluating the percentage biodegradability of the test substance. Concentration of inoculum i.e, sludge is 30 mg/l and initial test substance conc. used in the study is 100 mg/l. The percentage degradation of test substance is found to be 4% by BOD and 3% by HPLC. Thus, the substance 2,4-dinitroaniline was considered to be not readily biodegradable in water.