Casper Sam H. Hobbs Regional Wastewater Treatment Facility

Location: Casper, Wyo.

Client: Casper, Wyo.

Completion Date: 2004

Burns & McDonnell provided comprehensive facility planning services for the City of Casper’s Sam H. Hobbs Regional Wastewater Treatment Facility. The 10-million-gallon-per-day (MGD) project was completed for the City of Casper through its Joint Powers Board No. 2. The recommended improvements were funded using the Wyoming State Revolving Funding (SRF) loan program.

The facility plan focused on four areas in the wastewater treatment plant: the secondary treatment system, the effluent disinfection system, the biosolids dewatering and disposal process, and an odor control and digester gas cleaning system. Each system or process was evaluated based on existing and potential future regulations, treatment capacity, overall performance and detailed economic analyses.

The secondary treatment system was evaluated considering the Wyoming Department of Environmental Quality’s anticipated ammonia limit for the North Platte River. In order to minimize the economic impacts of the new standard, several alternatives were evaluated. The recommended improvements included converting the existing complete mix activated sludge process to a contact stabilization process. The improvements included replacing the mechanical aeration system with a fine-bubble air diffusion system and a new air blower facility. The existing chlorine gas effluent disinfection system was also evaluated. Due to safety and management considerations, the city chose to evaluate liquid hypochlorites and UV along with continued use of chlorine gas. The recommend approach was to replace the existing gas chlorine disinfection system with a liquid sodium hypochlorite system.

A detailed residuals management plan was also developed. Several dewatering and disposal alternatives and combination of alternatives were evaluated including belt filter presses, centrifuges, air-drying, land application, composting and land filling. The recommended approach was to construct a new dewatering facility that included either a centrifuge or belt filter presses and drying pads. The dewatering equipment selection will depend on the results of pilot testing of both technologies. Over the next several years, the city planned a public relations campaign to urge land application and composting. The current disposal approach is by land filling due to economic considerations.

The final component of the project was odor control and digester gas cleaning. Several odor control alternatives were evaluated including liquid scrubbers, activated carbon units and chemical addition. Since chemical addition provided a solution to two problems, the recommended approach was to construct a chemical feed system. Iron salts will be used to control various odor sources and to clean the digester gas before use in the cogeneration unit.

  • Rocky Mountain Region
  • Nitrification
  • Biosolids improvements
  • Odor control
  • Automation and supervisory control and data acquisition (SCADA)
  • Ferric residuals
  • State Revolving Funding (SRF)