DPRShield Water Treatment System for Failsafe LowEnergy Direct Potable Reuse

Potable water demand in California is expected to grow, especially as droughts and water shortages are likely to become more common. Compared to other new water sources, potable reuse of water requires less energy, but is not widely used because of the advanced treatment required and negative public perception. DPRShield is a new lowenergy, dual-barrier water treatment system for potable reuse that removes trace contaminants through two membranes—forward osmosis and reverse osmosis—and includes a dye marker in the draw loop between the two membrane barriers that enables the system to detect even the smallest breaches. If one of the membrane barriers is breached, a third barrier, the “Breach-Activated Barrier,” is activated and pushes the contaminants away from the clean water stream with a pressure differential.

A pilot study at Orange County Water District demonstrated that the DPRShield technology produces permeate with excellent water quality from highly contaminated and often variable-quality feed water. The DPRShield was used to extract water from the existing reverse osmosis concentrate produced at the Orange County Groundwater Replenishment System. The project produced water quality comparable to the full-scale system reverse osmosis permeate; and generated high quality permeate with respect to all contaminants examined (organic contaminants, disinfection biproducts, and other regulated and unregulated compounds) using water with a contaminant level seven times higher than the feed water into the full-scale reverse osmosis system. The results demonstrated that DPRShield required 70 percent less energy than desalination, 33 percent less energy than competing direct potable reuse technologies, and up to 50 percent less energy than long-distance state water project transfers.

This new paradigm in water reuse provides evidence that the purification system works as designed and provides a counterpoint to negative public perception. The results are promising and further demonstrations and design improvements of the DPRShield technology will be needed before ready for sale to early adopters for commercial use. In addition, for municipal direct potable reuse, further work will be required to satisfy regulatory requirements.