El Paso Water Utilities’ Fred Hervey Water Reclamation Facility
El Paso’s Fred Hervey Water Reclamation plant was built in 1984, along with a series of 10 injection wells for recharge in the Hueco Bolson. The 10-MGD (38,000-m3/d) capacity plant provides water for four main uses: maintenance of wetlands of ecological interest, irrigation of parks and a golf course, aquifer recharge (infiltration basins and injection wells), and industrial uses (e.g., cooling tower makeup water). Treatment processes for wastewater treatment include primary clarification, flow equalization, two-stage activated sludge with denitrification, anaerobic digestion, and biosolids dewatering/disposal. In addition, wastewater is treated to achieve potable water standards through lime treatment, sand filtration, ozona-tion, biologically active GAC filtration, and final disinfection. The final effluent (potable water quality) is made available for irrigation and industrial uses through the transmission system that also recharges the aquifer.
Capital and O&M costs are provided in Tables 9-3 and 9-4. All reclaimed water, regardless of intended use, distance from source, or quality of water, is billed at $1.24/kgal. This is substantially lower than the potable water tiered rate that ranges from $1.93 to $6.49/kgal.
El Paso currently reclaims a combined 10 percent of all treated wastewater from its four wastewater facilities with a goal to increase reclaimed water supply to 15 percent of all wastewater treated. The reclamation plant is undergoing a major expansion to incorporate a third treatment train that would provide redundancy to the treatment process and increase the plant’s capacity by approximately 2.5 MGD (9,500 m3/d). Other water supply alternatives were considered; however, the decisive factor for implementation of this program was based on cost and need to conserve the water. Comparative costs of water supply alternative are shown in the figure below.
Comparative costs for alternative water supplies for El Paso Water Utilities, from 2010. This figure includes relatively low costs for desalination concentrate disposal (via deep-well injection) for the brackish groundwater desalination system.
SOURCE: Irazema Solis Rojas, P.E., EPWU Water Reclamation Engineer.
costs (Figure 9-5). However, annualized capital costs may be equal to or greater than operating costs. The state of Florida reports that 72 of its 176 utilities (41 percent) provide reclaimed water to users free of charge (FDEP, 2010).
Of the nine utilities who provided data to the committee on their nonpotable reuse rates, on average, the reclaimed water rates represented 39 percent of the rates for traditional potable sources (with ratios ranging from 11 to 75 percent).2 While most of the
2 When utilities reported tiered water rates, the committee considered the third tiered potable rate for comparison, considering that most nonpotable reuse customers are large volume irrigators.
potable reuse facilities combined their water supplies such that no separate charge was applied, two utilities charged separate rates to potable reclaimed water customers. Like the nonpotable reuse rates, these potable reclaimed water rates represented only a fraction (17 and 67 percent) of the traditional potable supply rates. Given the small size of this dataset, these data are not presumed to be representative of reuse rates across the United States. Because the driving motivation for water reuse is shifting from environmentally sound wastewater disposal to water supply for water-limited regions, reclaimed water rates are likely to climb so that reclaimed water resources are used as efficiently as the potable water supplies they are designed to augment.