Influence of microalgae-ZnO nanoparticle association on sewage wastewater towards efficient nutrient removal and improved biodiesel application: An integrated approach

Abstract

Present investigation highlighted the capability of microalgae cultivation in sewage wastewater integrated with nanomaterial, addressing wastewater treatment and consequent improvement in lipid for biodiesel application. Herein, the isolated microalga Chlorosarcinopsis sp. MAS04, was cultured in primary treated wastewater (PTWW) and secondary treated wastewater (STWW) incorporated with Zinc Oxide nanoparticles (ZnO- NPs). The characterizations of ZnO-NPs were performed by analytical technique and cytotoxicity assay of microalga against nanoparticles (NPs) was carried out prior to the experiment. The nutrient reduction rate of Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorous (TP), and Total Organic Carbon (TOC) by microalga was found higher in PTWW as compared to the STWW when incorporated with the ZnO-NPs. Maximum biomass of 3.43 g/L and 2.14 g/L along with 1.9 and 1.5 folds increase in cellular lipid was recorded in the presence of PTWW and STWW respectively as compared to control (BG-11). The cellular lipids were converted to fatty acid methyl esters (FAMEs) by the process of transesterification and analyzed by Gas Chromatography-Mass Spectrometry (GC–MS). The cells developed in PTWW and STWW incorporated with ZnO-NPs were recorded with a higher amount of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) with controlled polyunsaturated fatty acids (PUFA). Biofuel properties were found in accordance with American and European guidelines. The present report suggested that the Chlorosarcinopsis sp. MAS04 -ZnO NPs association is capable of better nutrient removal from sewage wastewater. Therefore, the nano-bio hybrid opens a new paradigm for efficient wastewater treatment and consequent quality biodiesel production.