In the late 1990s, Silverthorne, Colo., began exploring options to eliminate chlorine gas at four of its wells and a booster station because of employee safety issues caused by gas leaks. The city’s water system serves 3,700 residential and light commercial customers from six wells, four of which are in populated centers. The average treatment rate, which doubles during the peak summer months, is approximately 1 million gal per day. In addition, the town faced an immediate compliance need to upgrade ventilation at its well sites—a capital expenditure approaching $10,000.
“You have to be very careful with chlorine gas, and our employees were having instances when they’d inhale some of the gas through their masks when changing the monitor on the bottles,” said Gene Emore, water and sewer superintendent for Silverthorne’s Public Works Department. “The system was working okay, but it wasn’t up to par with state health regulations.”
Tablet Chlorination Facing ongoing safety concerns and a hefty capital expense for compliance upgrades, the town of Silverthorne converted two wells and a booster station from chlorine gas to the Accu-Tab tablet chlorination system by PPG Industries with no increase in operating costs and no loss of residuals. Silverthorne considered onsite generation as an option, but the complexity and cost of the equipment at the time wasn’t acceptable. Instead, the city decided on tablet chlorination and began phasing in the systems on the four wells closest to the population base.
After experiencing ongoing problems with the first tablet chlorination system it installed on two wells, Silverthorne switched to PPG Accu-Tab PowerPro 3012 and 3075 systems for the remaining two wells and the booster station. A comparison of the total expense between Silverthorne’s chlorine gas and tablet chlorination systems showed that while the tablets were twice as expensive, the maintenance and safety expenses for gas more than offset the increased cost.
“This system eliminated the liabilities we had with the chlorine gas,” Emore said. “We’ve maintained our residuals and only have to clean it about every six months.”
Simple Chlorination
The Accu-Tab system combines a simple, patented chlorinator with slow-release calcium hypochlorite tablets to provide consistent and controllable chlorine dosages regardless of size and demand. Accu-Tab PowerPro systems include all components necessary for a turnkey chlorination system and are easily adaptable for automatic control and multipoint injection. The compact system does not require a separate entry building or room (like gas) and takes up a fraction of the space required for similar bleach or onsite chlorine generation systems. In most cases, maintenance is reduced to cleaning the chlorinator just once a year.
The 3-in. Accu-Tab SI (scale inhibitor) calcium hypochlorite tablets are formulated to help prevent scale formation inside the chlorination chamber, especially in hard-water areas. Engineered to perform reliably and consistently, the tablets are pressed rather than formed, ensuring their physical integrity. Accu-Tab chlorinators are NSF 61 listed as drinking water system components, while Accu-Tab tablets are NSF 60 listed as drinking water treatment chemicals.
