Moringa‐Seed‐Based Coagulant Removes Microcystins Dissolved in Water

Abstract

Toxic cyanobacterial blooms commonly occur in bodies of water used to supply drinking water, leading to the presence of high concentrations of toxins in the water. Among the cyanotoxins, microcystins are the most frequently encountered in aquatic ecosystems. They have been associated with animal and human intoxication, illness, and death. Most of the chemical and physical methods employed by water control managers to control cyanobacteria and cyanotoxins are neither cost effective nor efficient. As an alternative, using natural coagulants that are biodegradable and easily deployed for water purification in small human communities have been proposed. In the present study, 28 assays are carried out using the jar test to investigate the effect of stirring rotation (time and speed), pH, and aqueous extracts of Moringa oleifera L. seeds (AqMO) on the cells, turbidity, and removal of Microcystis aeruginosa cells and extracellular microcystins. Cell removal efficiency ranged from −22.6 ± 1.3 to 85.8 ± 0.6%, and the reduction in turbidity ranged from −14.0 ± 3.1 to 87.4 ± 0.3% as a function of the different treatments. According to the critical value predicted, an AqMO dose of 540 mg L−1 combined with an initial cell density of 10 × 105 cells mL−1 will completely remove M. aeruginosa cells and significantly decrease extracellular microcystins content (ca. 54.4 ± 7.9%). These results show promise for the development of effective treatments of potable water contaminated with cyanobacteria and microcystins in rural and isolated areas, thereby reducing the public health risks associated with these organisms.