Green Remediation Strategy Using Azolla pinnata: Heavy Metals Removal and Waste Water Ultra-Purification

Phytoremediation using aquatic macrophytes is a scalable and affordable technique. Hereby, this study aims to determine the potential of Azolla pinnata to enhance the chemical and biological properties of treated municipal wastewater from the Beni-Suef treatment plant, Dandil, as well as its capacity for heavy metal removal at two dilution ratios (25% and 50%). The propagation of A. pinnata for 14 days significantly increased pH, electrical conductivity, total dissolved solids, and total Kjeldahl's nitrogen in two tested concentrations, particularly at 50% by 8.5, 632.9, 627.7 and 1620%, respectively. However, the count of coliform bacteria was significantly decreased to less than 180 CFU/100 ml at 25 and 50% treatments. Water analysis showed that A. pinnata significantly decreased the concentration of Pb, Cu, Ni, Cr, Zn, and B. Biomass analysis implied differential affinity of heavy metals uptake and removal efficiency by A. pinnata biomass which is typically higher at 25% concentration. A 50% dilution ratio resulted in removal efficiencies of Ni (88.7%), Cu (30%), Pb (24%), Cr (17.2%), B (14.5%), and Zn (11.4%), whereas a 25% dilution ratio showed removal efficiencies of Cr (100%), Ni (82%), Cu (74%), Zn (68.5%), Pb (30%), and B (20.8%). Compared to 50% dilution, the use of 25% significantly increased fresh weight (230 g) and relative growth rate (and 0.043 g/day), and achieved the shortest doubling ~ 6 days after 14 days of growth. A. pinnata may serve as an effective and reliable phytoremediator for municipal wastewater, and its biomass could be a sustainable biorefinery platform for various biofuel industries.