Chemical imbalance: why one water park switched its water-chemistry system

Parks & Recreation, Dec, 2003 by Mike Moss, Clay Finney

With the adoption of the new water-sanitizing program at the Tropicanoe Cove aquatic center, dry calcium hypochlorite briquettes are now used in two "spray technology" systems to teed water sanitizer to the pool water. The current chlorinator uses dry solid calcium hypochlorite briquettes containing a minimum of 65 percent available chlorine by weight, and also all inhibitor to reduce the potential for carbonate scale associated with the alkalinity component of water.

The chlorinator incorporates three primary components: a briquette hopper, a manifold spray section and a discharge tank. The highly soluble briquettes are scooped into the unit's briquette hopper. Water from the pool enters the unit via an inlet port, and a spray manifold distributes the water onto a briquette grid, creating a chlorinated solution. The solution falls into the units discharge tank and is discharged into the pool's recirculation system. New oxidation-reduction potential controllers determine the amount of chlorine discharged.

When the new chlorination system was set up, a post-filter recirculation loop was added to the main pool recirculation system. The recirculation loop provides the inlet water supply to the chlorinators as well as the vacuum to evacuate the chlorinated solution from the units. The solution is drawn by vacuum from the chlorinators' discharge tanks to the facility's recirculation system. The vacuum is created by a venturi installed in the post-filter recirculation loop driven by a 1-horsepower pump. The venturi is installed on the discharge side of the pump, creating a flow through the venturi that provides the suction on the chlorinator's discharge valve.

Going Swimmingly

With the switch from sodium hypochlorite to calcium hypochlorite briquettes and spray technology feed system, maintaining consistently good water chemistry at the facility is easier, and water chemistry control in the vacuum delivery system is safer. Also, the entire system is much more user-friendly from an operations standpoint. Because calcium hypochlorite is a more stable chemical than sodium hypochlorite, it allows for better dosage control and excellent water clarity, and a proper balance in chlorine residual between the leisure pool and the plunge pool is now much more easily maintained.

Each morning, a member of the pool maintenance staff tops off the chlorinators' 200-pound-capacity briquette hoppers. There is enough dry calcium hypochlorite chemical stored in both units' hoppers to last for at least 24 hours of operation. The facility could actually fill the boppers every two days, but the once-a-day schedule allows maintenance staff to routinely check the equipment. Also, lifeguards check briquette levels several times a day, further enhancing the facility's safety regime. The only other scheduled attention to the unit is removing and cleaning its briquette grid approximately every two weeks (although cleaning intervals could be extended). This is a 30-minute procedure, which involves soaking the grid in a solution of muratic acid and water.