Sharing a wastewater system, pros and cons of a membrane bioreactor in Seeley Lake

RV park owners want to share a wastewater system with Seeley Lake and many experts see it as a good option for the town's wastewater challenges.

During last month's Seeley Lake Sewer District Board meeting, members heard about a type of wastewater treatment system possible for a new RV park south of Seeley Lake, which was presented as an option for wastewater treatment in Seeley more generally.

This system - called a membrane bioreactor, or MBR - has garnered attention in the past couple of decades as a "promising technology" for wastewater treatment and reuse, according to a 2023 study published in Membranes, which covers the science and biology of membranes. Officials at the meeting said a MBR could work well for Seeley Lake, but its main drawbacks - cost and public acceptance - may give pause.

A few pros are notable - the MBR is ready to go; the location is secured as part of the RV park; the capacity could account for the sewer district's waste and then some; MBRs treat waste to very clean standards; and these systems have had major success in other parts of the state.

Gary Chilcott - one of the partners on the RV park, called the Lazy Acres RV Park - bought an MBR to install in Williston, North Dakota - where he was working in the oil field wastewater industry - but ended up not needing it. Since then, it has been sitting in storage in Williston.

"I've been looking for a home for it," Chilcott said.

This is the MBR that would be used in Seeley, and if things moved forward, the company Chilcott bought the MBR from would install it. A person with specialized training, called a certified operator, would be needed to manage the facility.

A MBR operates like a traditional sewer system - though generally with a much smaller footprint - with different biological processes that allow for waste to be broken down and processed. A micro membrane filters the wastewater, allowing only treated water to go through the tiny holes that make up the filter. Anything else, like nitrates or other contaminants, don't pass through.

The MBR that Chilcott has treats waste to 2.2 milligrams per liter, much less than the 7.5 milligrams per liter required for treatment in some cases in Seeley's Special Management Area and the legally mandated 10 milligrams per liter for drinking water standards.

Treated waste runs into a drainfield, which would be part of the RV park's design, and in the RV park's case it would lay nearby underneath a grassy park. Chilcott said the MBR plant has an estimated capacity of up to 152,000 gallons per day of waste. The plant would take both liquid and solid waste.

The MBR won't get much wear and tear since it'll sit inside an insulated building, and Chilcott said if expansion was ever needed, an extra passageway for waste could be added - another tank, pump or pipe - negating the need to build a whole new system.

So, why doesn't everywhere use a MBR if they have all these pros?

Darryl Barton - former water quality scientist with Montana's Department of Environmental Quality who permitted various wastewater systems and is now a private consultant working on the RV park project - listed three reasons.

First, Barton said MBRs are a relatively new technology for municipal systems. Most communities already have a system in place, and when looking to make improvements, generally upgrade or tend to what they already have instead of spending money on something new, which leads to the next reason - cost.

Barton said there are a lot of things a community can do to improve an existing system that are cheaper than upgrading to a MBR. If there's an issue with a lagoon, for example, a community likely prefers to make the necessary improvements to the existing lagoon rather than installing a whole new thing.

Operation and maintenance costs are often identified as downsides to MBRs, but Barton said he sees those almost as a positive in Seeley's case. Typically, this cost is an issue if it's an upgrade to a system that's already been built, Barton said, but a centralized collection system doesn't currently exist in Seeley.

"In this case, I really believe, truly, that this is an opportunity for Seeley to solve the problem that's there that's cost effective," Barton said, pointing out that Chilcott already owns the MBR and a construction company, and that he contracts out engineers and scientists for the project, which Barton said keeps cost lower.

Additionally, Barton said overall costs would be much cheaper than the sewer project planned for Seeley Lake a few years ago.

The drainfield for that project was out of town and uphill, which required a lot more piping and pumps, leading to higher installation costs. The MBR project, located near the Seeley-Swan Medical Center, wouldn't require the extra pumping, pipes and lift stations the original project needed, Barton said.

If the sewer district board decided to move ahead with the MBR, the district would end up purchasing the MBR, whatever it's housed in and likely the permitting. The land it sits on would be leased from the owner of the RV park, Brandon Grosvenor. Barton said funding in the form of grants and loans often cover these costs.

The costs of the system not covered by grants or loans, like operation and maintenance and loan repayments, would be reflected in some way on a water or sewer bill for people living in the sewer district - which includes the RV park owners.

The third reason MBRs aren't used more comprehensively is the systems treat waste to a very high standard, which isn't necessary in all cases.

One project Barton mentioned was for the town of Butte. Barton said Butte had a wastewater treatment system in place, but with the challenges of an aging system and high levels of metals in the wastewater, a MBR was installed to treat wastewater to a higher standard. Now, the entire town's wastewater is treated by an MBR and it is the largest MBR project in the state.

A smaller system Barton brought up was near Wheat Montana in the Three Forks area. A new rest area was built that tied its wastewater system to the new Bridger Brewing about a mile away. The waste is treated to such a standard that it can be used for irrigation, and Barton said the plan is to use the treated water to fill toilets in the rest area.

"I feel like it's the best wastewater technology available right now," Barton said.

The Seeley Lake Sewer District Board meeting with an MBR presentation will be held on March 21 at 6 p.m. at The Barn and via Zoom. Find the Zoom link here: https://seeleysewer.org/