Utilizing Automation To Maximize Performance at the City of Lebanon Authority Wastewater Treatment Plant

Rerating and upgrading an existing treatment process within a tightly limited area requires both design and operational ingenuity. This paper details how one such innovative control strategy is used to achieve maximum operational flexibility and energy efficiency from an Integrated Fixed Film Activated Sludge (IFAS) process with automated anoxic/aerobic swing zones located both before and after the IFAS zones at the City of Lebanon Authority Wastewater Treatment Plant. The process optimization control system focuses primarily on maintaining effluent nitrogen goals and achieving process stability and energy efficiency. To accomplish this, the system continuously monitors the process ammonia and nitrate readings in an effort to qualify influent strength, sets zone specific dissolved oxygen (DO) setpoints to modify each zone’s reaction rate, changes the internal mixed liquor recycle rate (IMLR) to maximize anoxic nitrate treatment, brings swing zones in to and out of aerobic operation in order to supply treatment on demand as the process requires, and controls a bypass valve/flow for the upstream trickling filter which allows for the system to increase or decrease the total available carbon for denitrification in the pre-anoxic zones. Use of the system has allowed the plant to efficiently meet its permit requirements while maximizing the performance of its process.