Reclaimed Water Aquifer Storage and Recovery: Potential Changes in Water Quality
Year Released: 2007
Funding Partners: Bureau of Reclamation, California State Water Resources Control Board, Southwest Florida Water Management District
Total Investment: $200,000 (Cash)
Principal Investigator: Tracy Clinton, Carollo Engineers
Aquifer storage recovery (ASR) is defined as the storage of water in a suitable aquifer through a well during times when water is available and recovery of the water from the same well during times when it is needed. The water sources used for ASR include potable water, reclaimed water, and stormwater.
Goals and Objectives
- Describes the state of the practice of reclaimed water ASR
- Identifies wastewater constituents and water quality parameters of significance for designing, monitoring, and evaluating reclaimed water ASR
- Measures concentrations of contaminants at various stages of recharge, storage, and recovery of reclaimed water and analyze observed data with respect to attenuation mechanisms and rates to characterize water quality changes through ASR
Four operating reclaimed water ASR sites were selected for participation in the water quality monitoring study. These were the Englewood Water District in Englewood, FL, Manatee County Utilities in Manatee County, FL, the Tumbleweed Recharge Facility in Chandler, AZ, and the recharge facility in Bolivar, SA, Australia.
Findings and Conclusions
TOC, pH, and nutrient reductions observed in this study generally supported the theory that notable microbial and chemical activity occurs in the zone closest to the wellhead, where the influx of dissolved oxygen enhances many processes. The accuracy of field measurements of dissolved oxygen and oxygen reduction potential was called into question, and much of the data on these parameters was dismissed.
Pathogens and indicator organisms were rarely detected. Concentrations of regulated disinfection byproducts including total trihalomethanes and haloacetic acids decreased between recharge and recovery at three of four sites.
For trace organics, the recharge water was expected to be highly variable, and there was question as to how representative the single grab sample taken for each site was for trace organics, which are known to fluctuate diurnally in municipal wastewater systems. The most notable microcontaminant trend was with atrazine, which decreased at the three sites where it was detected. In general, the data were insufficient to claim biodegradation of trace organics to a degree that eclipsed source concentration variability at the four sites.
By observing changes in concentrations of over 90 compounds at four ASR sites with many variables, this study intentionally took a broad assessment of water quality changes in reclaimed water ASR storage. The study was designed to investigate the variables of aquifer characteristics, storage time, travel distance, recharge water quality, and operational history. The data support many aquifer process assumptions, such as enhanced activity near the well, but did not statistically support conclusions regarding specific degradation rates for most of the parameters observed. With further research, however, it will be possible to better define the subsurface processes and associated treatment effectiveness.