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Client:
City of Dell Rapids

Dell Rapids, SD

Key Features:

  • 750,000 gpd capacity
  • Pre-treatment includes spiral screen and grit removal
  • UV disinfection prior to discharge

Key Experience:

Wastewater Treatment Facility (SBR)

The City of Dell Rapids, SD, with a of population 3,705, was placed under a construction order as part of their new Surface Water Discharge Permit. Effluent ammonia levels over their permit limits had caused several violations and the South Dakota Department of Environment and Natural Resources (DENR) required upgrades to their system to address these issues.

The previous treatment process utilized an aeration lagoon, followed by a series of facultative lagoons. With a total project cost of $4.7 million, the new SBR system utilizes the existing aeration lagoon for equalization and another lagoon cell for sludge storage, which reduced the cost of the project for the City and provided more operational flexibility. The equalization basin reduced the peak flow design requirements of the new treatment equipment because the high flows can be diverted during a large rain event until the flows subside to or below the design capacity of the SBR system and then rerouted back through the new treatment system.

The SBR treatment process provided a cost-effective solution to meet ammonia limits as well as being set up for anticipated total phosphorus and total nitrogen limits. The DENR was consulted during the design process to help establish effluent limits. Once these limits are implemented, the treatment cycles can be modified to meet total nitrogen limits, while a chemical feed system may be needed to meet future phosphorus limits.