Naturally-Functionalized Antimicrobial Sand (f-sand) Using Moringa Oleifera Seeds

Moringa oleifera (Moringa) seeds contain a natural cationic protein (MOCP), which has been used as an antimicrobial flocculant for water clarification.  The main challenge with using Moringa seeds for this purpose is that they release other water-soluble proteins and organic matter, which increases the concentration of dissolved organic matter (DOM) in the water. The presence of this DOM supports the re-growth of pathogens in treated water, preventing its storage and later use.  We have established a strategy for retaining the MOCP, while removing the excess BOD.  First, the MOCP is electrostatically immobilized onto sand grains and then the excess BOD is rinsed away, inhibiting the growth of bacteria in the purified water.  The data indicate that the functionalized sand (f-sand) removes microparticles and pathogens from water, renders adhered E. coli bacteria non-viable, and significantly reduces turbidity of a kaolin suspension.  The surface charge and antimicrobial properties of f-sand were ascertained with confocal microscopy using fluorescent polymer nanoparticle and microparticle tagging and fluorescent (live-dead) staining of bacteria.  The reduction of DOM, which can contribute to bacterial re-growth, was demonstrated by a considerable reduction in the solution biochemical oxygen demand (BOD).  These results suggest that immobilization of MOCP onto sand can provide a simple, locally-sustainable process for producing storable drinking water.