Pathogen Decay during Managed Aquifer Recharge at Four Sites with Different Geochemical Characteristics and Recharge Water Sources

Recycling of stormwater water and treated effluent via managed aquifer recharge (MAR) has often been hampered because of perceptions of low microbiological quality of recovered water and associated health risks. The goal of this study was to assess the removal of selected pathogens in four large-scale MAR schemes and to determine the influence of aquifer characteristics, geo-chemistry, and type of recharge water on the pathogen survival times. Bacterial pathogens tested in this study had the shortest one log 10 removal time (T-90, <3 d), followed by Cryptosporidium oocysts (T-90, <120 d), with enteric viruses having the biggest variability in removal times (T-90, 18 to >200 d). Human adenovirus and rotavirus were relatively persistent under anaerobic conditions (T-90, >200 d). Human adenovirus survived longer than all the other enteric virus tested in the study and hence could be used as a conservative indicator for virus removal in groundwater during MAR. The results suggest that site-specific subsurface conditions such as groundwater chemistry can have considerable influence on the decay rates of enteric pathogens and that viruses are likely to be the critical pathogens from a public health perspective.