This novel study was completed by Bronwyn Humphries as a masters project which examined the microbial removal properties of coral sand to explore how it might be applied to onsite wastewater treatment in Kiribati. Laboratory based, unsaturated drainage experiments were undertaken using worked coral beach sand, to examine its drainage and effective microbial removal properties. Bacterial and viral indicators (E. coli, E. faecalis and MS2 phage) along with viral pathogens (adenovirus; echovirus; norovirus; rotavirus) were drained under gravity through coral sand-packed columns, serving as physical models of an effluent drainage field. The results show that coral beach sand has a higher affinity for viruses than bacteria. All organisms examined showed removal efficiencies over 4-log removal values (i.e. 99.99 % reduction). Attenuation mechanisms such as absorption and physical straining likely play a major role in the ability of coral beach sands to attenuate the microbial tracers used in this study. Field studies are required to verify the laboratory results. These findings could have important implications for the use of locally available materials, such as coral sand, to improve household onsite wastewater treatment in Kiribati and offer enhanced protection of groundwater resources and reduce diarrheal disease.