p Removal efficiency of various coagulants for Microcystis, Anabaena and Oscillatoria at different cell densities

Abstract

The continuous industrial growth increases the volume of pollutants discharged into the water, which induces Cyanobacteria in the receiving bodies. The removal of various cyanobacteria such as Microcystis, Anabaena, and Oscillatoria was explored to analyze their removal characteristics using different chemical and mineral coagulants. The chemical coagulants, including poly aluminium chloride (PACl), Alum, and mineral coagulants such as Loess and Illite, were tested to remove selected cyanobacteria. Results indicated that the removal rate increased with coagulant dosage regardless of the type of coagulant. The removal of selected cyanobacteria using chemical coagulant was found in the order: Microcystis > Anabaena > Oscillatoria. The PACl coagulant showed the most efficient removal rate for Microcystis, Anabaena, Oscillatoria. Removal rate of Microcystis conducted by PACl showed 92% at 100,000 cells/mL and 98.4% at 1,000,000 cells/mL whereas Illite showed lower 70% and Loess showed lower 50% in both 100,000 cells/mL and 1,000,000 cells/mL. The removal rate of Anabaena and Oscillatoria by PACl and Alum was higher 80%, while the other coagulants exhibited lower than 75% at 1,000,000 cells/mL. The removal rate of Oscillatoria by PACl was 80.1%, while the other coagulants exhibited lower than 70% at 1,000,000 cells/mL. Moreover, the mineral coagulants showed better removal efficiency at a higher concentration than low concentration during experiments. Therefore, removing cyanobacteria from water streams can be improved through coagulation by selecting a specific coagulant for a particular type of algae.