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Innovative UV Disinfection System Saves on Costs
Town of Telluride, Colorado gets creative to increase capacity
by Bill Hogrewe, Director of Engineering Services (RCAP)
The Town of Telluride sits at the end of a picturesque box canyon in the mountains of southwestern Colorado. Famous for skiing, music festivals, and summer recreation, the town has also found a very creative solution to disinfecting the wastewater created by residents and all those visitors.
The wastewater plant was originally designed with a conventional ultraviolet light (UV) disinfection system installed in the effluent channel. The disinfection system worked well until flows increased above 1.4 million gallons per day (MGD), when the plant had trouble meeting its effluent E. coli limit of 250 cfu/100 mL, even though the facilities were designed for 2.1 MGD. The plant operators and their consulting engineer, Briliam Engineering of Pagosa Springs, Colorado, set about evaluating several options to increase the effectiveness and reliability of the disinfection process. Increasing the capacity using conventional UV configurations would have been expensive and required space that just was not available.
The solution they arrived at was to utilize the effluent launders (troughs) on the three existing circular secondary clarifiers as the reactor basins for the UV disinfection process. Normally, flow in a clarifier goes over the weir and into the launder. The flow in the launder can go in two directions around the circumference of the clarifier toward a single collection box. The new configuration used a stop log to force the flow to go in only one direction around the launder and past a single point where the UV lamps were installed. The design of the system required calculations to determine UV dose, head loss, clarifier modifications, construction costs, and operation and maintenance costs.
The modifications allowed the use of lower-cost UV lamps that also used less power. Tests showed that the new system performed as well as the old system, with the added benefit that both systems could be run at times of very high flow. Thanks to this innovative approach, the town saved on major construction costs and continues to save on lower lamp replacement costs and electricity costs.
Special thanks to Bill Goldsworthy, Water and Wastewater Superintendent, Town of Telluride; Patrick O’Brien, P.E., Briliam Engineering; and Mark Dahm, P.E., Briliam Engineering for the information that went into this article.
RCAP’s 2014 Annual Report Now Available
2014 was filled with significant accomplishments and new programs that have strengthened our ability to provide a variety of resources to small rural communities across the country. Read the full report here.
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