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Indirect Potable Reuse Investigation in Tucson, AZ

Project: 13-09
Type: Scientific Investigation
Scope of Work

Program: Tailored Collaboration
Funding Partner: Tucson Water
Total Investment: $341,514 (Cash: $299,994, In-Kind cash and service: $41,520)

Principal Investigator: Larry Schimmoller, CH2M Hill


To meet the water needs of the greater Tucson Metropolitan area, Tucson Water is exploring the concept of potable reuse as a means to diversify and expand their water supply portfolio. However, implementation of the traditional treatment approach used in many locations around the world that includes microfiltration (MF), reverse osmosis (RO), and ultraviolet advanced oxidation process (UVAOP) is unattractive and unsustainable because of high capital costs, large energy demands, and the environmentally and costly challenge associated with disposing of the RO concentrate at this inland location. Therefore, an alternative and sustainable treatment approach for potable reuse is necessary that simultaneously provides multiple treatment barriers for organics and pathogens, adequately removes salt, lowers energy use, and mitigates the issues associated with concentrate disposal.

Goals and Objectives

The project will:

  • Test the viability of the alternative potable reuse treatment scheme through water quality testing and treatment process performance monitoring.
  • Test the viability of soil aquifer treatment as a pretreatment approach to nanofiltration, which would allow substitution of NF for RO at locations where possible.
  • Test the viability of using NF concentrate for crop irrigation through characterization of concentrate stream for constituents critical to crop growth and health.
  • Depending on Phase I testing results, compare ozone-BAC/GAC effluent quality when using splitstream NF treatment to full-stream NF treatment or compare virgin GAC performance to 3-month old BAC/GAC performance.

Research Approach

Task 1: Pilot Design. The pilot system will be designed to include NF, ozone, and BAC/GAC filtration and will be located on Tucson Water’s Reclaimed Water Treatment Plant site. Extraction water from the Sweetwater Recharge Basins will be provided by a well within close proximity to the site.

Task 2: Pilot Construction. The University of Arizona will provide three pilot skids for this research: (1) a RO/NF pilot skid located in a mobile trailer; (2) an ozone oxidation and disinfection pilot skid; and (3) a BACIGAC filter skid. Tucson Water will construct the pilot testing facilities including setting the equipment, electrical connections, mechanical connections, etc.

Task 3: Pilot Operations. The pilot will be operated in two 3-month phases of alternative pilot configurations. Side-stream NF treatment will be tested during Phase I for a period of three months. The testing protocol for Phase II, which will also last three months, is dependent on Phase I results but will include an additional filter column with virgin GAC to compare trace organic removal to BAC and/or full-stream NF treatment to compare finished water quality to side-stream NF treatment.

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