City of Big Sky WWTP // Big Sky, MT

City of Big Sky WWTP // Big Sky, MT



    Client Needs:


    The Big Sky, Montana Waste Water Treatment Facility could no longer afford to long-haul their biosolids to distant application sites. They determined in-vessel composting on-site was the best way to reduce land application risks and gain control of their end-product process. Their system needed to:

    • Operate in extreme temperature conditions;
    • Have minimal labor requirements; and,
    • Require minimal space.



    ECS Solution:


    A competitive bidding process selected ECS to provide five In-Vessel Containers to accommodate the City’s initial requirement to process 130 dry/tons/year—and included provisions to add seven more vessels if the need for capacity increased. The Compost Vessels were sealed and insulated with stainless steel interiors and specialized aeration floors. The Vessels were built on roll-off skids compatible with the locally available refuse container hauling trucks.


    The system was provided with the CompTroller compost control system, which provides automated control and monitoring of the process within the vessels. It modulates the amount and direction of air flowing through each vessel based on temperature measurements, user selected set-points, and process goals.


    This ECS system also uses exhaust air from the mixing building for the compost system’s process air, thus containing and controlling fugitive odors at their odor-sensitive site. The Container In-Vessel aeration system was installed partially below grade to accommodate the facility’s small footprint, abundant accumulation of snowfall and cold weather conditions. The vessels were equipped with a “cold weather package” that doubles the typical amount of vessel insulation found in standard applications.

    ECS also supplied a heavy-duty 425 cubic foot compost mixer, a vessel-loading conveyor, a trommel screen with a live bottom feed hopper, equipment for wood chip amendment drying, and miscellaneous conveyors and motor controls.


    To date, Big Sky remains a model for all WWTP’s in Montana and the nation. All of the municipal wastewater sludge produced at Big Sky's wastewater treatment plant is post-processed into a compost product that meets all of the EPA standards for land application.  The decision to make compost is consistent with other decisions to make the treatment facility 100% self-contained.  All of their wastewater is treated and stored through the winter months.  During the summer months 100% of the treated water is reclaimed for use as irrigation water on 2 local golf courses.  There is zero discharge to the Gallatin River.


    All of their compost product is sold every year to the public for $25/yd3. They have never given the product away for free.


    Capacity (tpy)




    ECS Technologies Employed

    CompTroller™ Automated Control & Monitoring System

    In-Vessel Container

    Low-friction Aeration Floor

    Reversing Aeration System

    POG Biofilter

    Horizontal Auger Compost Mixer

    Stationary Trommel Screen

    Start-Up Year



    Big Sky, Montana


    "We started up our facility in 2004 and it has been running continuously without issues for the past dozen years; even during our winters where the temperatures can hit -25F at times. All of our original equipment has been reliable, and our control system remains solid. We are happy with the system performance and the product support.

    We have beat up the vessels a bit however have not had to replace a thing in 12 years of continuous operation.

    When we started we were concerned about selling the compost. We charged for it from the beginning. We sell our compost for $25/yd3 and we have always sold all our product.


    - Ron Edwards

    General Manager

    Big Sky Sewer and Water District


    "The ECS compost system works and we are very happy with it. It’s reliable, and when it needs repair it is easy to fix. ECS support is good and we order replacement parts from them when needed. We sell our product to the public, landscapers mostly, and they love it. Our only issue is when the temperature drops below -30F. At that temperature we have had a few of the vessels freeze solid and we had to move them into a building to thaw them and restart the process."


    - Grant Burroughs

    Big Sky Wastewater Superintendent

    Big Sky, Montana


    Read more about Big Sky's Facility on our Comp Blog.


    Visit Big Sky WWTP online.