TRANSPORT OF BACTERIA AND VIRUSES THROUGH SURFACE SOILS FOLLOWING IRRIGATION WITH RECYCLED WATER

Due to an increasing national emphasis on wastewater reclamation for purposes such as aquifer augmentation and agricultural irrigation over potable aquifers and as opposed to disposal, there is potentially considerable potential for transport of bacteria and viruses from treated wastewater through the environment and into many drinking water supplies. In Hawaii, nearly all of the drinking water supply is obtained from unconfined groundwater aquifers under each island and there is a need to recycle more water on overlying golf courses. A study consisting of laboratory columns, field plots, and numerical simulation is underway to assess the potential for contamination of the potable aquifers on Oahu from bacteria and viruses present in recycled waters applied for irrigation. Bacteria and viruses have been observed to travel short distances through the native soils in laboratory columns, but they have not been recovered in field test plot lysimeters and numerical simulations predict that penetration into the surface soils will be limited to a few feet due to high adsorption and die-off. Molecular biological analyses of soils exposed to recycled water irrigation show bacterial population shifts compared to control samples exposed to potable water irrigation, however those shifts do not correspond to the dominant bacteria species present in the recycled water.