Achieving Limits of Technology (LOT) Effluent Nitrogen and Phosphorus Removal at the River Oaks Two-Stage Advanced Wastewater Treatment Plant

Abstract

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. KEYWORDSNitrogen removal, separate-stage denitrification, aerobic stabilization, phosphorus removal, advanced wastewater treatment PLANT DESCRIPTIONThe River Oaks AWTP is located at 8425 Sheldon Road in Tampa, FL. Figure 1 shows an aerial photograph of the River Oaks AWTP site. The plant has a capacity of 10 mgd and includes a two-stage biological treatment system that combines suspended growth carbonaceous biochemical oxygen demand (cBOD 5 ) removal and nitrification followed by suspended growth denitrification system with methanol addition. Figure 2 illustrates a process schematic for the River Oaks AWTP. Table 1 summarizes dimensions and volumes of important liquid treatment process units at the AWTP.Following preliminary treatment, primary clarification takes place in two circular primary clarifiers. Primary effluent is directed to the nitrification system (first stage) for carbonaceous BOD 5 removal and nitrification. This stage consists of three parallel aeration tanks, three 406 WEFTEC®.07