Preliminary Treatment

Preliminary treatment is a process that is performed to prepare the wastewater for the rest of the treatment process. Preliminary treatment at the Wastewater Reclamation Facility (WRF) consists of three separate processes; screening, pumping, and grit removal. Screening is a process that uses machines, called barscreens, to remove any large, untreatable, or unwanted materials before they cause problems further along in the treatment process. After screening, the water is pumped from the main wet well (where the water accumulates after screening) to the highest point in the facility, where the water will flow by gravity throughout the rest of the facility. In the grit removal chambers, the water is slowed down enough that the heavy solids settle out, but the lighter organics stay in suspension and flow to the primary treatment process. Both the materials collected in screening and grit removal are removed from the facility and brought to a landfill for disposal.

Schematic of preliminary treatment at the Des Moines Wastewater Reclamation Facility.
Main Pumps
Pump piping
Pump Motors