Centrate Equalization – What You Don't Control Can Hurt You

Abstract

Management of high ammonia dewatering return streams is key for plants that struggle to meet effluent ammonia limits. This paper focuses on approaches to high ammonia sidestream management to reduce the impacts of diurnal ammonia peaks and effluent ammonia excursions. The same principles may be applied to other sidestream sources (e.g., filtrate from a belt filter press), but the examples in this paper are related to centrate. When facility operational constraints or other factors prevent ideal load equalization from being implemented, flow equalization can still help mitigate ammonia excursions. A challenge with equalization basin operation is how to predict the daily outflow volume needed for true equalization. Important aspects of high ammonia sidestream management, such as determining the volume of equalization required, dewatering schedules, tank and pump design, desired outflow control, and the impacts of continuous or "trough-fill" high ammonia sidestream recycle are discussed. Examples from two Colorado wastewater treatment facilities are included to demonstrate these approaches.