Removal of cyanobacterial harmful algal blooms (HABs) from contaminated local park lake using Ganoderma lucidum mycelial pellets

Eutrophication and hypereutrophication in lakes foster harmful blue-green algal blooms, which pose a significant threat to the ecological health of freshwater reservoirs. This study investigated the effectiveness of the bio-flocculation approach using the Ganoderma lucidum fungus strain BGF4A1 to remove these harmful blooms, specifically targeting cyanobacterial species like Microcystis PCC-7914. Key flocculation parameters, cyanobacterial concentrations, adsorption kinetics, and pellet morphology were explored in this research. Our results demonstrate that G. lucidum can effectively remove up to 93.70 % of cyanobacteria (measured as chlorophyll-a absorbance), 75.28 % of chemical oxygen demand (COD), and 92.09 % of total suspended solids (TSS) under optimal conditions: an initial pH of 4, 1 % fungal volume (w/v), 48 h of contact time, and 100 rpm agitation at room temperature. Microscopic examination of water samples before and after treatment confirmed a significant reduction in cyanobacterial colonies, indicating the death or decline of the targeted organisms. Morphological analysis using field emission scanning electron microscopy (FESEM) revealed that Microcystis cells were deposited on the hyphae of the G. lucidum pellets, in contrast to the smooth surface of control pellets. These novel culture technologies show great promise as bio-flocculating agents for removing blue-green algae and potentially be adapted for microalgae harvesting in biodiesel production.