Orange County’s wastewater recycling program, a pioneering idea that’s already touted as the largest of its type in the world, is about to get bigger.

Big enough, in fact, to serve the tap water needs of about 1 million residents, according to the Orange County Water District and Orange County Sanitation District. Dubbed the Groundwater Replenishment System, the project produces water that is half the price of imported water, and is virtually immune to both drought and reductions in imports.