This book focuses on the better solution Nanotechnology offers compared to conventional methods of water treatment. Various methods of synthesis of reduced graphene oxide (rGO), its applications with special emphasis on water treatment have been discussed. Biogenic synthesis of rGO using plant extracts reported by previous workers is also covered in this Chapter and also encompasses laboratory work on bio-reduction of graphene oxide using the aqueous extract of Amaranthus polygonoides and its use in the preparation of its composite with silver nanoparticles and Moringa oleifera pulverized seed powder .