Tri-phasic engineered wetland system for effective treatment of azo dye-based wastewater

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.