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Moringa oleifera f-sand Filters for Sustainable Water Purification

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journal contribution
posted on 22.11.2017 by Boya Xiong, Bethany Piechowicz, Ziyuhan Wang, Rose Marinaro, Emma Clement, Taylor Carlin, Adam Uliana, Manish Kumar, Stephanie Butler Velegol
The purpose of this work is to determine parameters for the design of a Moringa seed sand filter for water purification. Moringa oleifera seeds containing cationic antimicrobial proteins have been used as natural coagulants for the removal of turbidity; however, a low removal efficiency and high residual organic levels limit their applications. In this work, Moringa seed extracts were used to reverse the charge of sand (f-sand) to 10 mV at a seed dosage of 5.6 g of seeds/m2 of sand. This f-sand filter demonstrated ∼4 log removal of 1 μm polystyrene particles and >8 log removal of Escherichia coli compared to <0.1 log removal for bare sand. Enhanced removal for particles and E. coli was dominated by attractive electrostatic interactions. Clean bed filtration modeling predicts a sticking coefficient (α) of 0.8 for f-sand compared to a value of 0.01 for bare sand. This α was further validated under a wide range of filtration conditions. Preliminary scale-up analyses suggest a point-of-use f-sand filter that requires a very small amount of seeds annually. The outcome of this work presents the scientific basis for the design of a water purification solution for developing regions, requiring only locally available resources and no use of synthetic chemicals or electricity.