Where the wild things flow

The good news is, with the recent installation of a new clarifier, Carbondale’s wastewater treatment infrastructure is churning along and ready to accommodate growth.

What is a clarifier and how does our wastewater return to the river without contaminating it?

“It’s important for people to understand that flushing a toilet is the start of a process, not the end,” said Public Works Director/ Interim Town Manager Kevin Schorzman. In late October, Schorzman and Utilities Director Mark O’Meara granted The Sopris Sun a tour of the waste treatment facility northwest of Town.

Guided through the plant, “your nose and ears tell you a lot,” explained O’Meara.

As verified by a strong odor, the pre-treatment building is the first phase of filtration, straining out toilet paper and other suspended solids, then pressing out the water to produce a concentration of solid waste for disposal at the landfill.

Further down the hill, a round, white building called a clarifier slowly gyrates the resulting liquid and sludge in large circles, allowing dense organic waste to settle at the bottom. Grease on the surface is skimmed off and the resulting water is sent to a snaking network of aeration basins.

In 2021, the Town purchased and installed this new clarifier for just over $1.557 million. It can process up to a million gallons of waste per day and allows for redundancy in the system. Two older clarifiers rest nearby, ready to act as back-up as needed. Sanitation depends on keeping the waste in motion and the new clarifier mitigates the potential for a bottleneck resulting from a mechanical failure.

The constant movement of air through the system keeps the water from turning anaerobic, aka allowing stinky bacteria to flourish without oxygen. Prior to 1976, the Town utilized a lagoon-style waste treatment system. According to O’Meara, the aerobic method mimics 30 to 50 miles of river. It’s an organic process that allows microbes to cleanse the water, releasing gases like phosphorus and ammonia.

Toward the end of the aeration basins, dark sludge containing aged microbes is piped to the beginning, seeding the stream with return flow to jumpstart microbial activity. O’Meara drew an analogy to sourdough starter.

“The trick is to keep it moving, all the time,” said O’Meara. The non-stop aeration, in more demand during certain parts of the day and year, makes the waste treatment facility one of the Town’s greatest energy sinks, according to Schorzman. To give an idea, the back-up generator holds 850 gallons of diesel fuel. The location of the plant, on a shady river bank, makes solar impractical. However, Holy Cross Energy supplies the electricity that powers the operation and has declared the goal of providing members with 100% renewable-sourced energy by 2030.

The aerobic method also makes waste treatment possible with minimal chemicals. The only added chemicals in the whole process are: a small amount of gas chlorine to disinfect water before it enters the Roaring Fork River, and a polymer to help bind organic solids that are buried and composted at the landfill.

The biggest upgrade in the history of the facility was in 1997, to accommodate the development of River Valley Ranch (RVR). That work included a new headworks building, sludge thickening disposal, an aeration basin building, increased air blower capacity, a disinfection contact basin and a garage for the tanker truck and sludge transfer. “Pre-existing aeration basins were converted to digester basins,” said O’Meara. “A new interceptor sewer line was also installed which connected the RVR development to the facility.”

The plant is currently operating at roughly 80% capacity. According to O’Meara, future upgrades to accommodate greater growth would mean “additional digester capacity and possibly aeration basin capacity.”

The plan is operational with zero debt, “thanks to good planning,” said Schorzman. He credits O’Meara with turning a projected $12 million upgrade in 2007 — to resolve escaping odors — into a $2.5 million solution, by studying the process and identifying efficiencies.

Nearby, samples from Carbondale’s entire water system are regularly tested to assure quality and sanitation.