AWWA WQTC69245

Solids contact clarifiers are the flagship of softening plants in the Midwest and Florida. Although it is one of the oldest technologies in the water treatment industry, it is also one of the most misunderstood and neglected unit processes. This work focuses on the proper operating and control of solids contact clarifiers and introduces a simple, straightforward algorithm programmed into a supervisory control and data acquisition system (SCADA) for generating and maintaining the proper amount of solids in the center cone of a solids contact clarifier. Study conclusions include the following: the key to optimized solids contact clarifier operation is the generation of an inventory of large uniform diameter solids that remain in suspension; solids contact clarifiers can be difficult to operate due to the solids removed on a daily basis as compared to the amount of solids inventory that is maintained in the center cone; and, mass balance combined with simple algorithms and utilization of an existing SCADA system can create a system, which reliably manages solids and produces excellent water quality. Includes figures.