Cyanobacteria Removal by Coagulation/Flocculation with Seeds of the Natural Coagulant Moringa oleifera Lam

Abstract

Eutrophication of water bodies has resulted in increased population of cyanobacteria that can produce toxins capable of causing health problems in humans. In conventional water treatment, coagulant aluminum sulfate are used most commonly, although the production of non-biodegradable sludge and indications of damage to health have led to a search for other coagulants that are less harmful to the environment and to human health, such as the seeds of Moringa oleifera Lam. The objective of this study was to assess the efficiency of moringa seeds as a coagulant for the removal of cyanobacteria cells. To carry out the coagulation assays, deionized water was artificially contaminated with cells of the cyanobacteria Microcystis protocystis, in order to obtain samples with different initial turbidity. This water was submitted to coagulation/flocculation with different dilutions of a stock solution of 1% moringa seeds. In order to assess cell removal, readings were made in aliquots of 5mL of samples analyzed by triplicates counting on sedimentation chambers using an inverted optical microscope, according to the Utermöhl method. Concentrations above 200mg/L from the 1% solution of moringa seeds gave the best cell removal, about 91%. Color and turbidity removal were found to be dependent on the initial turbidity of the water sample and the concentration of coagulant. Coagulation with moringa seeds gave satisfactory results in reducing the number of cyanobacteria cells. However, since complete removal was not obtained, further studies are necessary.