South Dakota Wastewater System Upgrades

Challenge: The private client facility is undergoing a production expansion from 18,000 head per day to 26,000 head per day. The expansion is anticipated to have minimal impact to existing flows, but loadings will increase by 50 percent. Having newer, more efficient DAF units is anticipated to compensate for the increased loadings without any change to the downstream treatment process. DAF effluent will be treated by the existing anaerobic lagoon. Solids will be directed to the existing belt filter press. The existing DAF units are more than 40 years old and in need of replacement.

Solution: The project includes demolition and replacement of the two existing circular DAF units with two new rectangular DAF units, new skimming tank, HVAC improvements, interior wall improvements to the existing DAF building, piping, electrical upgrades throughout the building, and controls.

Construction sequencing will allow for continuous operation of the DAF process at all times while the work is underway. The new rectangular DAF units have a much smaller footprint than the existing circular DAF units. Two rectangular DAF units fit within the footprint of one of the existing circular DAF units, which will result in more room for storage. In addition, the DAF units will have more hydraulic capacity than the existing units. Each rectangular DAF unit has a treatment capacity of 2,000 gpm.

The design process started with pre-selection of a DAF manufacturer. The HR Green team worked with multiple vendors and together with JMC developed a list of acceptable manufacturers. HR Green developed specifications and bidding documents for competitive bidding, reviewed and compared all bids, and made a recommendation of award. A manufacturer was then selected to be the basis of further design. The DAF system was commissioned in summer 2016.

Benefit: The project increased hydraulic capacity and more efficient use of space due to the installation of new rectangular DAF units. The client has noted a 90 percent reduction in the use of polymer since the new DAF units have been in service.