Chlorella vulgaris-mediated Bioremediation and Valorization of Urban Wastewater, from a circular economy approach

Abstract

The potential of Chorella vulgaris to bioremediate urban wastewater (UW) and produce value-added biomass was studied. Biological oxygen demand (BOD5), chemical oxygen demand (COD), nitrate, nitrite, ammonium, phosphorus, and coliform bacteria in UW were determined. Proteins, carbohydrates, lipids, and fatty acid profile (FAP) were analyzed in the biomass. The phytotoxicity of treated wastewater (TW) was evaluated using Lactuca sativa seeds to determine its suitability for irrigation. After 4 days of cultivation in 100% UW, C. vulgaris removed 99% of nitrogen compounds and 97% of phosphorus, eliminated 99% of coliform bacteria, and reduced COD and BOD5by 39.70% and 73.20%, respectively. After 8 days, protein and carbohydrate contents were lower than those of the control culture, while lipid increased 1.9 times. Additionally, C. vulgarisproduced 90.1% of fatty acids, mainly oleic and polyunsaturated fatty acids, including omega- 3 and omega- 6, which are attractive to the food, nutraceutical and pharmaceutical industries. The importance of FAP determination in C. vulgaris is emphasized to identify the most appropriate applications. The L. sativa test revealed a reduction in TW phytotoxicity as the remediation time increased. Based on phytotoxicity indices, TW exhibited minimal to moderate phytotoxic effects. This study highlights the potential to obtain biotechnological products from an otherwise devalued effluent, contributing to a circular economy by reutilizing TW in productive applications.