Magazine article Parks & Recreation

Chemical Imbalance: Why One Water Park Switched Its Water-Chemistry System

Magazine article Parks & Recreation

Chemical Imbalance: Why One Water Park Switched Its Water-Chemistry System

Article excerpt

For more than a century, Columbian Park in Lafayette, Ind., has been a place for visitors to enjoy high-quality leisure time with family and friends. In June 1999, the Lafayette Parks & Recreation Department enhanced the visitor experience at the 43-acre park by opening the Tropicanoe Cove family aquatic center.

The $4.6-million city parks project, part of a master plan developed in 1998 through open public meetings and surveys, encompasses 16 acres inside the park. The aquatic center features a 640-foot lazy river, a 168,000-gallon zero-depth leisure pool, a 33,000-gallon plunge pool, plus many other aquatic features, including a 300-foot tube slide, a water playground and two high-energy drop slides. The center is open Memorial Day through Labor Day and, besides family fun, offers scheduled activities such as aquatic fitness programs. Attendance at the center in 2002 was 76,000.

Maintaining proper water chemistry in the center's three distinct water bodies (leisure pool, plunge pool and lazy river) is of paramount importance. State regulations require 1.0 to 3.0 parts per million free chlorine residual and pH values of between 7.2 and 7.8 at all times. With highly fluctuating and, often disparate bather loads between the plunge pool and leisure pool, maintaining consistent chlorine residual presented a major challenge for facility staff. Because of this challenge, last year the center changed water-chemistry systems. Included in that change was switching from sodium hypochlorite to calcium hypochlorite as the sanitizing agent.

Problems in the Pool

The center wanted to find an alternative to using sodium hypochlorite For several reasons. Although effective in performing its sanitizing task, commercial sodium hypochlorite has certain problematic inherent characteristics. Chief among these was safety. The center's staff was concerned about the potential for personnel exposure to injury using the high-solution strength liquid chemical under a pressurized system.

There were also maintenance concerns associated with sodium hypochlorite usage. Commercial sodium hypochlorite is highly corrosive to metals, and presented a high potential for creating a corrosive environment inside the equipment building, adversely affecting pumps, piping valves and surroundings. There were also concerns regarding the common problem of chemical metering pumps becoming air-bound owing to sodium hypochlorite off-gassing.

Another concern was the inconsistent concentration of sodium hypochlorite. Commercial sodium hypochlorite solutions are subject to degradation and byproduct formation because of time, temperature and other factors. The concentration of chemical delivered to the aquatic facility and stored on site in two 500-gallon tanks often varied. Although the facility's water-chemistry control system compensated for losses in solution strength, it required pumping more solution to meet the chlorine-residual requirements in the pool. In the long run, using the degrading product cost more because the facility had to use higher volumes of the chemical to achieve the desired results.

In addition, commercial sodium hypochlorite contains sodium hydroxide (caustic soda), which is added by manufacturers to help stabilize the bleach solution. High sodium hydroxide levels in the pool water can produce higher levels of total dissolved solids, which can adversely affect water clarity, feel and taste.

Because chlorine residual values in the water would fluctuate, operators often had to set the facility's oxidation-reduction potential controller's set-point (or operating range) high to ensure that state regulations were met; this practice further increased chemical usage. These fluctuations were caused by a number of factors, including limitations of the original pool chemistry-control system in adjusting feed rates to address the disparate bather loadings between the leisure pool and plunge pool. …

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