Azo dye decolorization through fermentation and mineralization in an anaerobic-aerobic system

• Grant number: 18/24269-2
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): April 01, 2019
• Status: Discontinued
• Field of knowledge: Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
• Principal researcher: Eugenio Foresti
• Grantee: Jean Maikon Santos Oliveira
• Home Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 15/06246-7 - Biorefinery concept applied to biological wastewater treatment plants: environmental pollution control coupled with material and energy recovery, AP.TEM
• Associated scholarship(s): 20/11860-4 - Microbial dynamics and metabolic pathways in a two-phase anaerobic digestion system treating azo dye and sulfate, BE.EP.DR

Abstract

Effluent from textile industries, generated during the processing of cotton products, is characterized by high salinity levels and color, requiring a special treatment prior to disposal into water bodies. This scenario is worsened in regions with water shortages, e.g. the northeastern Brazil, where is located one of the major production centers in Brazilian textile industry. Azo dyes are the most widely used in dyeing processes over the world and are present at high concentrations in wastes from textile factories. These dyes are recalcitrant to biological treatment and their partial degradation originates carcinogenic and toxic aromatic amines. In this study, a novel system is proposed for the complete degradation of the azo dye Direct Black 22 (DB22) and aromatic amines produced after color removal process. Reductive decolorization will take place in an Acidogenic Structured Bed Reactor (ASTBR) inoculated with specialized microbial biomass. An Upflow Anaerobic Sludge Blanket reactor (UASB) coupled in series is intended for sulfate and organic matter removal, although partial sulfate reduction can occur at the preliminary unit. Phase separation on the anaerobic digestion can minimize exposure of methanogenic communities to the azo dye toxic effects, beyond to reduce competition between sulfate and azo for reducing equivalents. Moreover, a Structured Bed Reactor (STBR) subjected to continuous aeration will be used for degradation of the byproducts generated during reductive cleavage of the azo bond. Phylogenetic characterization of the microbial consortia will be carried by using 16S ribosomal DNA sequencing technique. Also, shifts in microbial community diversity will be assessed by analysis of denaturing gradient gel electrophoresis fingerprinting. Degradation pathway of the DB22 will be proposed based on mass spectrometry for detection and identification of the metabolites from azo degradation. (AU)