<i>Moringa oleifera</i> and Polyaluminum Chloride: Coagulant Combinations for Cyanobacteria Removal in Drinking Water

Cyanobacteria represent a significant problem for water treatment systems due to their ability to form blooms, release harmful toxins, and decrease the efficiency of water treatment processes. This study investigated the efficacy of a natural coagulant and its combination with a chemical coagulant to remove cyanobacteria from water. The combination with natural coagulants reduces residual aluminum concentrations in the sludge and treated water and lowers process costs. A dosage of 20 mg L^-1 of <i>Moringa oleifera</i> was identified as the most effective for the removal of turbidity (≈82%), color (67-76%), and cell density (88-97%). The proportion of 75% <i>Moringa oleifera</i> and 25% polyaluminum chloride was the optimal condition for cell removal (95%) and resulted in a low residual aluminum concentration in the treated water (0.030 mg L^-1). The seasonal variation of cyanobacteria in the C/F/DAF treatment showed that 50% <i>Microcystis aeruginosa</i> and 50% <i>Cylindrospermopsis raciborskii</i> achieved the most effective removal of turbidity (94%) and cell density (≈99%). The color removal for this cell proportion was 80%. Based on the results, treatment efficiency was not affected by cell density or cell morphology. The analysis of dissolved organic carbon and total dissolved carbon showed no variation for most of the samples after C/F/DAF treatment. This study demonstrated the efficiency of combining coagulants, highlighting the potential of <i>Moringa oleifera</i> as a sustainable water treatment alternative.