In the far western corner of Texas, in the middle of the arid Chihuahuan Desert, El Paso receives just nine inches of rainfall each year. The city of 700,000 is prone to river droughts and the surface water supply is unreliable.

Combined with population growth and climactic changes that affect water supplies, the situation has made diversification of water supply strategies a priority for the city and El Paso Water (EPWater). As part of a long-term and proactive water supply strategy, EPWater is building an Advanced Water Purification Facility (AWPF). PCL Construction is currently in pre-construction on the project, part of a joint venture with Sundt. Wastewater treatment facilities that produce non-potable water are not new. Water from those facilities can be used in gardens and toilets but is not suitable for drinking and cooking. The AWPF in El Paso will be the first “direct-to-potable” facility in the U.S., meaning water flushed down the toilet or shower drain will return to the tap as purified drinking water.

The science is clear and proven in other parts of the world on a large scale. PCL’s Project Director, Jay Brown, says it is important to understand that the water going into the AWPF is not sewage. It is “secondary effluent” and has already been through several important treatment processes, including primary and secondary clarifiers, biological nutrient removal, and first stage polishing.

The secondary effluent then flows to the AWPF, where it will be further processed through a robust treatment train with several steps. They include membrane filtration, reverse osmosis, advanced oxidation with ultraviolet light and hydrogen peroxide, granular activated carbon for peroxide quenching, and chlorine disinfection. “Once it’s gone through these robust treatment processes, and with extensive commissioning and testing requirements in place, it’s ready for drinking,” says Brown, who worked for three years on Singapore’s state-of-the-art NEWater project, considered a global leader in direct-to-potable water treatment.

The new facility in El Paso will treat up to 10 million gallons of water per day, which will be mixed with brackish groundwater and introduced directly into the potable water distribution system.

In other places, purified water is used for irrigation, injected into aquifers or pumped into reservoirs. For example, PCL has partnered with the City of San Luis Obispo in California, to install an innovative membrane bioreactor treatment at that city’s wastewater treatment plant. It will significantly reduce the plant’s environmental footprint and improve the wastewater by removing nitrates and trihalomethanes. The water is not potable but is used for various irrigation purposes in everyday necessities such as parks and schools. The city is required to discharge approximately 1.5 million gallons per day into the local creek to support the steelhead trout population, but also diverts approximately 300 acre feet for reuse.

The need for water reuse will only grow. More than two billion people worldwide cannot readily access clean, safe water, and with climate change and increased demand, that number will grow. California has been through multiple extreme droughts in recent years, including the most recent one that scientists say was the driest three-year period on record. It left the state's reservoirs at dangerously low levels, so regulators have introduced new rules to let water agencies use direct-to-potable systems. It is a big step for a state that struggles to find reliable sources of drinking water for its 39 million residents, and many water agencies in the state are already moving to take advantage of the changes.

Colorado also uses advanced water purification but takes the extra step of returning the water to a reservoir so it mingles with water from other sources. This “indirect-to-potable” method was a first step in gaining public trust.

Reusing wastewater comes with an additional ecological benefit. Around the world, secondary effluent is discharged directly into rivers and seas, impacting the health of human and aquatic ecosystems. It can bring excessive levels of nitrogen and pathogens and cause damage to coral reefs and other coastal environments such as seagrasses, salt marshes, mangroves, and intertidal ecosystems.

Fully treating and reusing wastewater conserves this precious resource. “We could be taking all that water, treating it and either injecting it back into aquifers or right back into the potable system,” says Jeffrey Newman, PCL’s operations manager in California. “It would provide a safe source of potable water and reduce the impact of sending all that wastewater into the ocean ecosystems.”

With a history of over 470 water and wastewater projects, PCL Construction builds for tomorrow by integrating innovative, climate-resilient solutions.