Due to unprecedented population growth in the late 1970s and early 1980s, Hillsborough County, FL, developed an aggressive capital improvement program, including a 3-phase construction program to increase the capacity of the River Oaks Advanced Wastewater Treatment Plant (AWTP) from 3 mgd to 10 mgd while improving plant performance to significantly reduce the nutrient discharges to Tampa Bay. When construction of the final phase was completed in June 1989, the County had met its goals of protecting water quality in the Tampa Bay Estuary System, expanding treatment capacity and simplifying system operation by improving process units at the River Oaks AWTP. For the past 20 years, this innovative treatment process has provided flexible and reliable treatment performance that has enabled Hillsborough County to achieve the highest quality treated wastewater in the region.