Life Cycle Assessment for the Environmental Sustainability of the Immobilized Acid-Adapted Microalgal Technology in Iron Removal from Acid Mine Drainage
Sudharsanam Abinandan, Kuppan Praveen, Suresh R. Subashchandrabose, Kadiyala Venkateswarlu, Mallavarapu Megharaj
Abstract
Acid mine drainage (AMD) resulting from mining activities is a serious threat to the environment, affecting aquatic and terrestrial life. In this study, two acid-adapted microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, were assessed for their ability in iron (Fe) removal from an AMD sample in nonimmobilized and immobilized systems. Use of free and immobilized cells exhibited 46–48% and 65–79% Fe removal, respectively, after 48 h of incubation. Compared with free cells, immobilized cells exhibited no apparent changes in morphology and granularity, as revealed by flow cytometry analysis, after their exposure to AMD samples. The second derivative spectra from Fourier transform infrared spectroscopy showed vibrational stretching for proteins and hydroxyl groups in immobilized cells. Thus, the immobilization technology offers a protective mechanism in acid-adapted strains against Fe present in AMD samples. Analysis of the immobilized acid-adapted microalgal technology by life cycle assessment (LCA) revealed its environmental sustainability because of less contribution to global warming and limited fossil fuel consumption. We demonstrated that the immobilized acid-adapted microalgal technology is much superior to calcined eggshell–microalgal or conventional limestone systems indicated in the literature for AMD treatment. Thus, this is the first study describing the potential application of microalgal cells entrapped in alginate beads in a greener and economical approach to treat AMD for sustainable mining.