OC World Host Joone Kim-Lopez explores groundwater issues with Michel Markus, General Manger of the Orange County Water District, and Cathy Green, President OCWD Board of Directors. The system is the world’s largest purification system for indirect potable reuse, providing up to 130 million gallons of water per day to roughly 2.5 million residents in north and central Orange County. It takes highly treated wastewater from the Sanitation District and purifies it. Through a three-step process of micro filtration, reverse osmosis, and ultraviolet light with hydrogen peroxide.