Wastewater Treatment Facility (SBR)


Wastewater facility design
Involves Planning for growth
and pending regulations

Growing Dell Rapids community builds
system that will foster future growth

Project Owner:
City of Dell Rapids, SD

Key Features:

  • New Sequencing Batch Reactor (SBR) wastewater treatment facility
  • Pretreatment includes spiral screen and grit removal
  • Ultraviolet disinfection

The City of Dell Rapids, SD, population 3,705, was 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 City completed a study to evaluate several treatment processes which included Submerged Attached Growth Reactor (SAGR), conventional activated sludge, extended aeration, trickling filters, membrane bioreactor, moving bed biofilm reactor (MBBR) and Sequencing Batch Reactor (SBR). The evaluation considered capital cost, long-term operation and maintenance, along with future discharge limits. With consultation from DGR Engineering (DGR), the City ultimately selected the SBR treatment process which enabled them to adapt easily to future permit limits. Cost, ease of operation and the ability to be easily expanded to meet future growth were factors in the decision.


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 reduces the cost of the project for the City and provides more operational flexibility. The equalization basins also reduce the peak design requirements of the new treatment equipment because the peak flows can be diverted during a large rain event until the flows subside to or below the design capacity of the SBR system.

The SBR treatment process provided a cost-effective solution to meet future 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 anticipated future limits. Once these limits are implemented, the treatment cycle can be modified to meet total nitrogen limits, while a chemical feed system can also be added to meet future phosphorus limits.

DGR designed the system to be easily expandable if the City grows beyond the original design capacity. The new facility has a 750,000 gallon-per-day capacity and was constructed with a 20-year design life, using an estimated population of 5,900.