Primary Clarifier Process Modeling: Successes and Challenges

Primary clarifier performance is commonly assumed to be consistent across all operating conditions. In fact, performance has been shown to be a function of primary clarifier design, operating conditions and, most importantly, influent wastewater characteristics. Using a mathematical model developed specifically for primary clarifiers, five case studies are presented that include examples where modeling was shown to be successful and examples where modeling proved challenging. The equation described by Wahlberg (2006) can be successfully applied to historical and/or field data to develop a model that can predict primary clarifier performance over a range of surface overflow rates (SORs) and influent conditions. However, model fit was shown to be variable between the five case studies. These case studies provide insight into considerations when modeling primary clarifiers. Organic removal by primary clarifiers is complex due to the varying nature of raw wastewater. Therefore, engineering judgment must be appliedtomodeling results