Aquifer Storage and Recovery (ASR) for Ecosystem Restoration: Kissimmee River ASR System, Florida

Abstract

Aquifer storage and recovery (ASR) is a major water storage and management component in the Comprehensive Everglades Restoration Plan (CERP). In south Florida, the high permeabilities of Eocene and Oligocene marine limestones, with a thick overlying confining unit are a well‐suited for ASR. The Kissimmee River ASR (KRASR) system, located at the confluence of the Kissimmee River and Lake Okeechobee, was a CERP “pilot system” to evaluate ASR feasibility at interior locations. Four recharge‐storage‐recovery cycles of increasing duration and volume were completed between 2009 and 2013. The largest and longest cycle resulted in 1 billion gallons recharged and recovered through a single well. The surface water pretreatment system at KRASR was unique compared to drinking water ASR systems. Surface water was pumped through a pressurized media filter then disinfected using flow‐through UV chambers prior to recharge. No chemicals were added during pretreatment. Many studies were completed during the testing program. A geotechnical evaluation confirmed that microfracturing of the limestone could occur at pressures slightly greater than typical operating pressures (30 to 50 psi), but microfractures were unlikely to propagate upward into the confining unit. The changing redox environment of the Upper Floridan Aquifer showed that arsenic was mobilized during recharge but was attenuated during storage and recovery such that arsenic concentrations in recovered water were below the 10 μg/L criterion after cycle test 1. Frequent sampling of recharge water showed that the UV disinfection system was ineffective resulting in total coliform exceedances. The KRASR pretreatment system is being redesigned to improve regulatory compliance.

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

“…The microorganism concentrations considered in the exposure assessment were retrieved from environmental studies that enumerated fecal indicator bacteria and pathogen concentrations in Florida surface water targeted for ASR source waters [30]. No dilution or additional treatment/disinfection was incorporated into the risk assessment.…”

“…While the U.S. EPA risk threshold for primary contact recreation is significantly greater, 3.6 × 10 −2 , and is a per event risk threshold, a more conservative approach when interpreting risk was applied in this study, especially given that the ASR management practices will require surface water, prior to recharge, to be treated to potable water standards [9]. 30 (4)…”