The City of Caldwell WWTP required improvements to its solids handling and digestion processes. Keller Associates provided preliminary design, final design, bidding, and construction administration of the Solids Handling and Digestion Improvements Project.

The $7 million project included a new digester and primary sludge pump station, modifications to the waste gas system, and demolition of multiple digesters, a control building, and a lab building. Preliminary design also included evaluations of biosolid treatment options as well as future thickening and dewatering options. Electrical design and phasing were a critical component of the project to keep operations up and running while the old primary sludge pump station and digester control building were being replaced. The project involved energy-saving measures, such as a linear motion mixer and biogas storage. With the completion of this project, the City now has the necessary capacity to reliably meet Class B biosolid requirements.