Eco-phytoremediation using Azolla microphylla enhances heavy metal removal, water quality, and biomass valorization in semi-arid wastewater treatment
Noureddine Benguennouna, Djilali Benabdelmoumene, Said Dahmouni, Zineb Bengharbi, Wasim S. M. Qadi, Hamizah Shahirah Hamezah, Ahmed Mediani
Abstract
Water scarcity and untreated wastewater pose serious threats to environmental and public health, especially in semi-arid regions such as northern Algeria. This study assessed the potential of Azolla microphylla , a fast-growing aquatic fern, for phytoremediation of household wastewater over a 35-day period. Ponds treated with A. microphylla showed marked improvements compared to untreated controls. Chemical oxygen demand (COD) decreased by 94.9 %, biochemical oxygen demand (BOD₅) by 89 %, and total suspended solids (TSS) by more than 93 %. pH levels stabilized, and electrical conductivity remained mostly unchanged, indicating minimal ionic leaching. Heavy metal analysis revealed significant reductions in Pb (80 %), Cd (80 %), Cu (76 %), Zn (84 %), Fe (83 %), and Mn (85 %). A. microphylla accumulated high concentrations of these metals, with bioconcentration factors (BCF) ranging from 32.5 (Cd) to 82.1 (Pb), confirming its hyperaccumulation capability. Translocation factors (TF) for Zn, Cu, and Mn were elevated, indicating efficient internal mobility and phytoextraction. A 20.8 % increase in chlorophyll content (a and b) indicated enhanced photosynthetic activity, while biomass production reached 160 g DW/m², following a logistic growth pattern. These results highlight A. microphylla’s effectiveness in improving wastewater quality and its potential for sustainable biomass valorization in semi-arid environments.