Utilizing Mixed Cultures of Microalgae to Up-Cycle and Remove Nutrients from Dairy Wastewater

Abstract

This study explores the novel use of mixed cultures of microalgae-<i>Spirulina platensis</i>, <i>Micractinium</i>, and <i>Chlorella</i>-for nutrient removal from dairy wastewater (DW). Microalgae were isolated from a local wastewater treatment plant and cultivated under various light conditions. The results showed significant biomass production, with mixed cultures achieving the highest biomass (2.51 g/L), followed by <i>Spirulina</i> (1.98 g/L) and <i>Chlorella</i> (1.92 g/L). Supplementing DW (75%) with BG medium (25%) significantly enhanced biomass and pH levels, improving pathogenic bacteria removal. <i>Spirulina</i> and mixed cultures exhibited high nitrogen removal efficiencies of 92.56% and 93.34%, respectively, while <i>Chlorella</i> achieved 86.85% nitrogen and 83.45% phosphorus removal. Although growth rates were lower under phosphorus-limited conditions, the microalgae adapted well to real DW, which is essential for effective algal harvesting. Phosphorus removal efficiencies ranged from 69.56% to 86.67%, with mixed cultures achieving the highest removal. Microbial and coliform removal efficiencies reached 97.81%, with elevated pH levels contributing to significant reductions in fecal <i>E. coli</i> and coliform levels. These findings suggest that integrating microalgae cultivation into DW treatment systems can significantly enhance nutrient and pathogen removal, providing a sustainable solution for wastewater management.