The city is considering either distributing the water through a new 25-mile pipeline to the St. Vincente reservoir, which would require the construction of a large tunnel, or placing the pipeline across the bottom of the reservoir, which would eliminate the tunnel and thus reduce the overall cost and timeline for the project.

Another option is to bring water through a 10-mile pipeline to a smaller reservoir. "We are moving forward with this program, keeping all these options open, but in order for us to meet our deadline [of 2021 or 2023], there will come a time when we need to make a decision," Labonte says.

By the time the entire program is complete, it will be contributing about a third of the city's water supply by 2035, says Brent Eidson, deputy director of external affairs for San Diego. Currently, the city imports about 85% to 90% of its water supply. "We know that if we create it here in our own region, it's a reliable supply for our community," he says.

Challenges Remain

One of the biggest obstacles to potable-reuse projects is lingering public resistance. Perhaps most famously, opponents of "toilet to tap" were able to completely derail the city of San Diego's first effort to develop a potable-reuse project in the late 1990s.

But public attitudes seem to be changing, if only out of necessity. "I think in places in the Southwest, where water is scarce, there is greater awareness of the problem," says Wendy Broley, water-reuse leader at Brown and Caldwell. Droughts and wildfires have brought, "front and center," the problems associated with water scarcity, she says, adding, "As a result, municipalities are recognizing that now is the time to put in place something that is going to help them diversify their water portfolios."

In drought-plagued regions of Texas, two DPR  projects were built recently in Big Springs and Wichita Falls with virtually no public opposition, officials  there say.

Greg McIntyre, president of CH2M Water, agrees that public attitudes are definitely shifting toward IPR, in which water is treated to an advanced level, then, typically, blended with another source of surface water in a reservoir, river or other body of water before it enters a drinking-water plant for further treatment.

"For sure, the public is softening around IPR," he says. But DPR, in which wastewater is treated to the highest level of treatment, then put back into the water distribution system, is a different story. "Around DPR, it becomes very specific to the situation. … The more dire the circumstances, the softer [public attitudes] get toward direct potable reuse," he adds.

Much of the public already has been drinking purified, recycled water through IPR. For example, residents who live in the service area of Virginia's Upper Occoquan Service Authority have been safely drinking water produced from IPR facilities since the 1970s, with little fanfare or controversy. Moreover, any community downstream of the Colorado River are drinking water that has received somewhere along the line some wastewater discharges, although that water is treated before it gets to them, Labonte notes.

Another project that broke barriers in public perception is the Orange County Groundwater Replenishment program, a groundwater IPR program that has been operating successfully since 2008. The 70-mgd facility recently completed an expansion to 100 mgd, and the Orange County sanitation and water districts are considering an additional 30-mgd expansion.

Going Ceramic