Informing ASR Treatment Practices in a Florida Aquifer through a Human Health Risk Approach

Area of Science:

• Environmental Science
• Microbiology
• Public Health

Background:

• Aquifer storage and recovery (ASR) is a method to augment water supplies, but its use of drinking water regulations is debated.
• Pre-treatment requirements for ASR are questioned, particularly regarding microbial inactivation.

Purpose of the Study:

• To assess the impact of storage time in the Floridan Aquifer on pathogen inactivation.
• To evaluate human health risks associated with ingested ASR water.
• To determine if aquifer storage mitigates risks to acceptable levels.

Main Methods:

• Quantitative microbial risk assessment (QMRA) was employed.
• Data from inactivation of *Escherichia coli*, *Pseudomonas aeruginosa*, poliovirus type 1, and *Cryptosporidium parvum* were analyzed.
• Risks of gastrointestinal (GI) infection and disability-adjusted life years (DALYs) were calculated.

Main Results:

• The risk of GI infection fell below the 1 × 10^-4 threshold by days 31 (*E. coli*), 1 ( *P. aeruginosa*), 52 (*Cryptosporidium parvum*), and 80 (poliovirus).
• DALYs per person per year dropped below the WHO threshold (1 × 10^-6) by days 27 (*E. coli*), <1 (*P. aeruginosa*), 43 (*Cryptosporidium parvum*), and 72 (poliovirus).
• Storage time significantly reduced microbial contamination and associated health risks.

Conclusions:

• ASR storage time significantly contributes to pathogen inactivation.
• Geochemical conditions within ASR zones also play a role in microbial inactivation.
• Findings support a risk-based approach to ASR recharge water treatment, considering natural inactivation processes.