A so-called "toilet to tap" system that takes human wastewater and turns it into drinkable water is undergoing a $150 million expansion, keeping Orange County home to the world’s largest water purification system for potable reuse.

The Orange County Water District’s Groundwater Replenishment System began operations in 2008 and has since supplied more than 112 billion gallons of purified water, according to the system’s website.

The concept of turning water from sewage systems into pure drinking-quality water has long been controversial in Southern California -- and elsewhere that the "toilet to tap" label has been applied to reclamation projects.

In Orange County, water officials say their reclaimed product, which would have been dumped into the Pacific Ocean if not for the plant, is near-distilled quality.

Proponents of reclaimed water strongly dislike the phrase "toilet to tap," arguing the water goes through many stages of filtration from start to finish.

The system -- which cost $481 million to build -- purifies wastewater using a three-step process of microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide, according to the website.

After the water is filtered, it provides 20 percent of the total water supply to the district’s 19 municipal water agencies and 2.4 million residents.

Despite the large output, the replenishment system uses less than one-third of the energy needed to desalinate ocean water, and less than half the energy needed to import water from Northern California.

The mega-million-dollar expansion will increase the water output from 70 million gallons per day to 100 million gallons per day, said Shawn Dewane, president of Orange County Water District.

The district estimates construction will be complete by 2015.



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