Lewiston, Idaho's wastewater treatment plant dates back to the 1950s, and surprisingly several of the original components are still in operation today. Although the equipment had been maintained, several equipment failures, and the associated emergency repairs, opened the City's eyes to the need for additional investment. One of the largest expenses for the facility was the aeration basins. The City utilized coarse bubble diffusers and controlled the aeration using manual operator adjustments. Additionally, the aeration capacity was insufficient, leading to several process upsets.
Over the past few years, the City made several critical decisions to improve its aeration basin system. Their approach eventually led to the construction of a new treatment process configuration within the existing basins. Additionally, the mixing, aeration, and aeration controls were all replaced to reduce energy usage and improve process control. The improvements, including compressed gas mixing and ammonia-based aeration control, have recently started up on the approximately $35 million project. This presentation will discuss the steps the City went through, their decision-making procedure to select the equipment, and the process and energy improvements that have been observed.
