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Big Sky WWTF and Effluent Disposal Improvements


Big Sky, Montana

About the Project

AE2S, teamed with another consultant, was selected by the Big Sky Water and Sewer District (District) for preliminary and final design engineering and construction administration to upgrade and expand the WWTF.

The objective was to support diversification and expansion of its exiting effluent reuse and disposal options. The District currently operates a Sequencing Batch Reactor (SBR) wastewater treatment system followed by a multimedia filtration system to produce effluent for irrigation.

The District recycles 100 percent of their treated effluent as irrigation on three golf courses. Significant growth is pushing the limits of the existing system.

Project Details

Date: 2017 – Present

Client: Big Sky Water and Sewer District

Key Project Elements
  • WWTF Expansion with Limits-of-Technology Treatment
  • Very Low Nutrient Limits
  • Discharge Permitting
  • Public Communications

Membrane Bioreactor (MBR)

Membrane bioreactor (MBR) technology was utilized in the upgrades project with a focus on achieving limit-of-technology nutrient removal and a start on removing compounds of emerging concern (CECs). The maximum month capacity will be increased to 1.4 MGD while maximizing the treatment capacity of the site to enable future expansion planned to increase capacity to 2.8 MGD.

Additionally, advanced treatment (advanced oxidation process (AOP) and biological activated carbon (BAC) filtration), which would further improve the District’s effluent reuse options to include potential indirect potable reuse (IPR) was evaluated. These processes would be retrofitted into the District’s existing Filtration Building and this project may be pursued in a second phase treatment upgrade.

Expanding WWTF Capabilities

Existing infrastructure was repurposed to expand solids treatment and handling capabilities. The existing SBR basins will be converted to Aerobic Digesters and a flow equalization tank. Alternates included designing a dewatering centrifuge to replace their existing belt filter press and Phase 2 expansion of the biological treatment basins to maximize the site treatment capacity.

The WRRF Phase 1 Improvements consists of the following components:

  • New Headworks Building with dual coarse and fine screening and grit removal
  • New Treatment Process Basins for biological nutrient removal
  • New Membrane Bioreactor (MBR) Facility with 0.04-micron membranes, process blowers, permeate pumps, RAS pumps, chemical feed equipment, electrical and mechanical rooms
  • Conversion of existing sequencing batch reactor tanks into Aerobic Digesters and a flow equalization tank
  • New Motor Control Center and backup power generator
  • New effluent reuse system
  • Site/Yard piping improvements
  • Site work and landscaping
  • Reuse and effluent storage piping modifications (including a new clearwell for high-pressure reuse pump station)
  • Upgraded Instrumentation and Control/SCADA System
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Big Sky Water and Sewer District WWTF and Effluent Disposal Improvements