Quantifying the effect of Managed Aquifer Recharge on the microbiological human health risks of irrigating crops with recycled water

Managed Aquifer Recharge (MAR) is increasingly being used for water recycling via aquifers and recovery for irrigation. Quantitative Microbial Risk Assessment (QMRA) was used to assess the human health risks from irrigation using reclaimed water and to evaluate the reduction in risk where MAR is used for irrigation management. Four MAR sites (Shafdan, Israel; Nardò, Italy; Bolivar, Australia; and Sabadell, Spain) that use reclaimed water for crop and/or park irrigation were evaluated, and the risk to human health was quantified in terms of DALYs (Disability Adjusted Life Years). The results indicated that median risks for all scenarios and pathogens evaluated were acceptable (<10−6 DALYs) with the exception of risks from accidental aerosol ingestion and bacterial pathogens at the Nardò site. MAR was found to be one of the most important treatment barriers in terms of log10 inactivation credits and hence a useful tool for recycled water irrigation management. The Shafdan site relied almost completely on the MAR treatment to reduce the human health risks from irrigation to acceptable levels. For the Nardò site MAR was also an important barrier, where if MAR had not been used as part of the irrigation system the risk would be unacceptable for protozoa and viruses. The Bolivar and Sabadell sites had much larger and more technologically complex recycled water treatment systems and as such MAR was not a critical barrier in managing human health risks.