Rainwater is a major source of drinking water in developing countries. Roof-harvested rainwater is generally microbiologically contaminated and thus need to be treated effectively to meet drinking standards. Filtration of rainwater with silver nanoparticles coated on sand enhances the microbial removal efficiency. In this study, the filtration parameters of treating rainwater with biologically synthesized nanosilver coated sand are optimized. Of the various synthesis methods, the biological method of was chosen due to benefits such as cost-effectiveness and eco-friendly nature. Silver nanoparticles was synthesised using with papaya fruit extract and then coated on sand. The synthesized nanosilver coated sand was subjected to characterization methods such as Energy Dispersive Spectroscopy and X-Ray Diffraction analysis. With silver coated sand as control, multiple long duration tests were performed to treat rainwater with nanosilver coated sand to find the optimal values for filtration parameters such as filter bed depth and Empty Bed Contact Time (EBCT). The crystallite size of the nanosilver coated sand was found to be 43.8 nm. The optimal values for filter bed depth and EBCT was found to be 12 cm and 15minutes respectively. The rainwater treated with nanosilver coated sand met drinking water standards IS 10500: 2012 until the media got exhausted.