Abstract
Synthetic dyes are a major class of compounds used in the textile industry. The effluents released from these industries are carcinogenic and mutagenic in nature and pose potential threat to all life forms. Here, we designed a novel tri-phasic engineered flow through wetland system (TEWS) with three specific microenvironments (tri-phasic aquatic systems) integrated in a defined sequence to effectively treat azo dye-based textile wastewater. Tank 1 with free-floating and emergent aquatic macrophytes create anaerobic/anoxic microenvironments and facilitate reduction of the azo dye molecules. Tank 2 consists of submerged macrophytes which create an aerophilic microenvironment that direct the oxidation of carbon compounds along with nitrification. Tank 3 with free-floating plants and aquatic animals acts as filter feeder intended to remove suspended solids and colour, as well as residual carbon. The strategically designed TEWS attributes to 76%/87% of dye/chemical oxygen demand removal. The morphological toxicity test of plants and fishes illustrate the nontoxic nature of treated effluents. Thus, TEWS not only decolorizes the azo dye but also removes its toxic and mutagenic components.
Highlights
Azo dyes represent a major class of colorants used in textile industries that contain one or more azo bonds (–N = N–)
Azo dyes get decolourized by splitting the azo bonds in sequential bio-redox conditions, forming aromatic amines and further breakdown into simpler compounds.[3,4,5]
The persistent anoxic microenvironment in Tank 1 favored denitrification that led to the azo bond breakdown of aromatic amines
Summary
The constructed wetland mimics a natural ecosystem, wherein all the trophic conditions are balanced and perform their role and in the process bring about wastewater treatment by relying entirely on the living systems.[3,24,25,26] TEWS symbiotically enables ecological selfdesign[25,27] with an ecosystem boundary that can selforganize.[25,26,27,28,29,30] The efficiency of designed TEWS mainly depends on the root zone interactions between soil, contaminants, plant roots, and a variety of microorganisms with indigenous tropical microenvironments in each designed tanks This primary objective is to address the current problems in the field of textile/azo dye industry by providing in situ redox microenvironments with living systems for effective degradation of azo dye
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