Plant-derived coagulants as sustainable alternative for aquaculture wastewater cleanup

The rapid increase in population and the ongoing depletion of freshwater resources have raised global concerns about water scarcity. In response to this critical issue, there is an urgent need to reuse wastewater by removing contaminants. Chemical coagulants have been excessively used due to their high efficiency, but they come with disadvantages. In this study, a novel approach was explored by utilizing the whole plant (leaves, stem and roots) of two underexplored medicinal plants, Catharanthus roseus and Ocimum tenuiflorum, to evaluate their efficiency in treating aquaculture wastewater. Coagulation experiments were conducted using jar test apparatus. Adsorption of the pollutants on the coagulants through sweep flocculation, pore entrapment and charge neutralization mechanisms were observed through Scanning Electron Microscope (SEM) studies. Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) analysis revealed the key functional groups -OH, C=C and C=N on the coagulants that contributed to flocculation of pollutants. The overall experimental study revealed that all coagulant types were efficient in treating aquaculture wastewater at an optimal dose range of 0.3-0.4 g/L. Catharanthus roseus roots were better at removing turbidity (99 %) followed by total suspended solids (98.3 %) and total dissolved solids (96.3 %). Chlorides, sulphates, phosphates and nitrates were efficiently removed with a blend of C. roseus and O. tenuiflorum. Electrical conductivity was reduced effectively by up to 99 % with O. tenuiflorum seeds. These overall findings indicate an eco-friendly, sustainable solution for aquaculture wastewater treatment.