County consultants recommend algae-based septage treatment; questions remain on cost, siting and who will pay

Ravalli County commissioners on June 2 heard a preliminary engineering report and public comment on options for a centralized septage receiving and treatment facility, with consultants promoting a receiving station, a rotating-belt primary filter, a bioengineered algal secondary treatment and municipal discharge to the Town of Stevensville or the City of Hamilton as the preferred approach.

The report’s presenter said the meeting’s purpose was “to further develop the alternatives, go through a recap of things that have been updated from the last public meeting, and then discuss potential ranking of how to promote the preferred alternative for a septage treatment facility in Ravalli County.” The consultant identified the bioengineered algal system as the top-ranked liquid-treatment alternative on operational-cost and public-acceptance grounds and recommended partnering with a municipality for effluent disposal.

Why it matters: County staff and consultants said a centralized receiving facility would reduce the county’s current reliance on on‑site land application of septage, a practice that raises local concerns about nutrient loading and emerging contaminants such as PFAS. Commissioners were presented with capital and operating cost estimates, site comparisons and a funding plan that relies heavily on grant awards; several pumpers and Stevensville residents said the per-gallon fees implied by the plan would make the facility uneconomical without additional subsidy or regulatory changes.

Most important details and recommendations - Recommended system. The consultant described a facility with an enclosed receiving station (headworks), primary screening (a rotating belt filter), and a secondary treatment train based on a greenhouse-enclosed bioengineered algal “wheel” system that the consultant said has lower aeration horsepower and…