The ultraviolet low-pressure (UVLW), closed-vessel treatment system from Engineered Treatment Systems (ETS) is designed for high-quality wastewater, filtered effluent or membrane-treated wastewater destined for reuse, especially in water-stressed regions.

The system’s plug-and-play, low-energy 800-watt amalgam lamps have a 12,000-hour life span (approximately one year) and five-year sleeve life. They can be configured horizontally, vertically or parallel for treating flows from 300 gpm to more than 15 mgd.

“Most reuse is indirect potable reuse, IPR. But in many parts, water-stressed states are turning to direct potable reuse,” says Jon McClean, president of ETS.

IPR blends treated water with a natural water source, such as an aquifer or reservoir, while direct potable reuse treats wastewater to drinkable standards and returns it upstream of a water treatment plant or directly into a potable water distribution system.

Since most water-stressed areas are located in hot climates, they also face high energy demands from the use of air conditioners and other cooling units.

“So we find that water stress and power stress go hand-in-hand,” McClean says. “The UVLW uses an amalgam lamp, which is almost 40 percent efficient. Most other lamps are between 10 and 15 percent efficient.”

To further optimize energy efficiency and water quality, ETS uses CFD (computational fluid dynamics) modeling to better understand fluid movement inside the reactors and across the UV lamps, turning portions of the system on and off as needed.

“We realize that fluid flow isn’t symmetric, therefore the lamp arrangements are not symmetric,” he says. “We pack the lamps closer in higher-velocity zones, and where we have low velocity we pack fewer lamps. In one reactor we might have a 16-lamp design with 15 on top and only one on the bottom.”

McClean compares wastewater movement inside the reactor to that of a river. “Think of how a river flows around the bend. There are areas where the river is bursting around, and there are areas where there is backwater flowing the other way.”

In the treatment process, water flowing at a rapid velocity is exposed to the UV lamps for a short period of time.

The modular system, with six to 45 lamps, treats between 2 mgd and 4 mgd of effluent in temperatures from 32 to 113 degrees F.

“To get to 12 mgd, we have two or three of them in parallel. Most plants run at about 40 percent capacity with an evening peak,” he says. As flow builds, a second or third system comes online.

“The real step forward is we now treat wastewater like we do drinking water,” he says. “It’s all being measured; it’s all being treated. We can’t afford to waste energy.” 877/885-4628; www.ets-uv.com.