Lying in wait, 32 newly installed ultraviolet tubes are nestled inside their modules.
In a few weeks, their glow will permeate millions of gallons of partially treated effluent in the final step before the water is released into the Big Wood River.
"This is really going to be a showpiece," said Mike Herrera, plant supervisor at the Ketchum-Sun Valley Wastewater Treatment Plant. "All of this equipment is the latest and greatest that the industry has to offer. It's really state of the art."
The first phase of the three-year, $7.4 million improvement project is within a month of completion. Phase one involves installation of the UV system along with major electrical upgrades.
In February 2004, Ketchum and Sun Valley voters approved a bond measure to finance the project.
The plant—which is located south of Ketchum near state Highway 75—is owned jointly by the cities of Ketchum and Sun Valley. All capital costs for major upgrades are split between the two, while operating costs are determined by the percentage of flows, said Steve Hansen, utilities manager for the city of Ketchum.
Although treating wastewater with UV is not new, the process has been refined.
"Its efficiency has gone way up and the cost has gone down," Hansen said.
The ultraviolet light process is 100 percent effective in killing bacteria, he said, an improvement over the current chlorine system that is in the 90 percent range.
The plant meets federal Environmental Protection Agency requirements now, but in 2006, the agency will impose stricter regulations.
Besides cleaner effluent being released into the river, no accompanying disinfectant chemicals will be present, Hansen said.
Although the percent of remaining chemicals is very small, it can have an effect on aquatic life and downstream users, he said.
Once the UV system is online, the 150-pound compressed cylinders of chlorine will be removed from the wastewater treatment facility, taking with them a potential environmental hazard, Hansen added.
As part of the electrical upgrade, a Scada computer system was installed. The system is capable of gathering and analyzing real-time data, which allows for monitoring and controlling the plant remotely.
A new generator is ready to replace an older model, ensuring wastewater continues to be treated in the event of a loss of power.
"Sewage doesn't stop during a power outage," Hansen said. "The waste stream continues to go through the plant and into the river."
During a high-flow period, he said, the system can receive 125,000 gallons of wastewater in one hour. That volume underscores the importance of a back-up system.
The project is approximately one month behind schedule due to bad weather and a few snags in the construction process, Hansen said.
"It's part of a process of construction," he said. "This was a major project. We were delighted there were few (changes)."
Phase one was the most extensive and difficult phase, but city staff is taking no breaks.
They're currently engineering the second phase: installation of another aeration basin.
"None of this is cheap stuff," Herrera said. "The city of Ketchum has always allowed us the best tools to do our job. We're very fortunate we get total support from the mayor and the City Council."
Without that support, Herrera said, the community would feel the effects.
"We recycle one of the world's most precious commodities," he said. "We take our jobs very seriously."