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Comparison of Chemical Composition of Reclaimed and Conventional Waters

Project: 06-06
Year Released: 2015
Type: Scientific Investigation

Program: Principal
Funding Partner: Bureau of Reclamation
Total Investment: $419,492 (Cash: $289,992, In-Kind cash and service: $129,500)

Principal Investigator: Shane A. Snyder, Ph.D., Southern Nevada Water Authority


Across the US and around the globe, agencies, regulators, and the public often question the water quality produced by IPR projects.  The proposed research set out to demonstrate the water quality produced by two major types of IPR practiced in the USA and compare to the water quality currently consumed through conventional drinking water treatment in model cities in the USA with various degrees of de facto reuse.

Goals and Objectives

The objective of this project was to compare the water quality of engineered potable reuse systems to the water quality of de facto (non-planned) potable water reuse systems.  A further objective was to compare an advance water reuse treatment system to an infiltration reuse system.  Parameters to be compared include emerging contaminant occurrence, byproduct formation potential, and regulated constituents occurrence.

Research Approach

Based on an extensive literature review, consultation with participating water agencies, and discussion with the Project Advisory Committee (PAC), the team developed an analytical roadmap to comprehensively evaluate water quality from seven sites in the USA.  The participating facilities were comprised of five drinking water utilities with known wastewater impact to the source water ranging from essentially zero to 30% and two indirect potable reuse (IPR) systems creating purified drinking water from municipal wastewater effluent source water. The team analyzed water samples provided from all seven locations quarterly for one year using the analytical roadmap endpoints. In addition, historical data from the facilities was reviewed and compared. Results from historical datasets and analyses conducted by the team were analyzed using various statistical tests and platforms to show a meaningful comparison for a diverse range of water quality endpoints among the sites.

Findings and Conclusions

All water quality parameters from all facilities were well within the ranges required for compliance with the US Environmental Protection Agency’s Safe Drinking Water Act. Thus, regardless of source water quality, water treatment processes employed were fully capable of providing drinking water of compliant quality.  For nearly every parameter measured, the IPR systems provided lower concentrations of measured water quality constituents, such as trace organic contaminants and disinfection byproducts, as compared to conventional drinking water facilities using wastewater impacted source waters.  The IPR system using reverse osmosis and advanced oxidation prior to groundwater injection produced the highest purity water evaluated.  The IPR system without advanced engineered treatment relied upon natural attenuation during soil infiltration and subsequent groundwater harvest had extremely high efficiency, yet some resilient trace organic substances and salts were present in the finished drinking water.  Regardless, this study demonstrates that both advanced engineered treatment and natural infiltration can produce extremely high-quality water suitable for potable use using a source water of typical municipal wastewater effluent. Moreover, this study demonstrates that communities relying on de facto reuse, that is significant contribution of wastewater into the source water, generally have more detectable constituents at higher concentrations than either of the IPR systems evaluated.

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