ClorTec® on-site sodium hypochlorite generators: European ATEX-certified model (left); model approved for use in U.S. and other countries (right)
Contaminants from people and the environment are constantly introduced to recreational waters such as swimming pools and spas. As a result, a disinfectant must be present at all times to reduce the hazards of these contaminants and eliminate the potential for adverse health affects. Disinfectants used for aquatic applications must be active in small concentrations and retain their activity for extended periods. The choice of disinfection method is typically based on the treatment type and its compatibility with the source water supply; the type and size of the pool; the bathing load; and the operations, management and supervision arrangement.
Chlorine-based disinfection technologies are by far the most commonly used treatment globally for aquatic applications. However, pool operators have increasingly sought alternative disinfection technologies for a variety of reasons, including:
- the hazardous nature of handling chlorine and its storage requirements
- chlorine has become more regulated, increasing the cost of its use
- corrosion of equipment and building metals from chlorine vapors in mechanical rooms and/or storage rooms
- chlorine-related accidents or injuries to facility operators
A chlorine alternative growing in popularity
Among aquatic disinfection alternatives, on-site generated sodium hypochlorite is seen by many as the most effective replacement for commercial forms of chlorine. On-site generation of sodium hypochlorite has been a key process in water treatment for municipal and industrial applications for more than 25 years. It is a dilute form of disinfectant compared to chlorine gas or concentrated commercial hypochlorite. As a result, handling, transportation and containment are easier and safer.
There are numerous benefits to using the on-site process compared to other forms of chlorine:
- savings of 50 to 75 percent in annual chlorine costs and pool-related chemicals
- improved inactivation of microorganisms
- increased water quality by reduced disinfection byproducts
- reduced cost of pH adjustment
On-site generation also eliminates the need for certain U.S. requirements such as OSHA process safety management training, risk management planning and purchasing and transportation of HazMat chemicals that are required when dealing with pressurized chlorine gas.
How on-site generation works
The process begins with using water from a standard hose bib connection on a fresh water line in the mechanical room. The water then flows to a small 10-in cartridge filter to remove dirt from the city water supply. The water then flows to a set of water softeners that remove the calcium from the supply water. The softened water then flows to the brine tank. The salt the system requires is contained in the brine tank, not in the pool.
Once the water mixes with the salt in the tank, the softened brine water flows to another 10-in cartridge filter to remove any dirt that may be in the brine tank. The brine water then flows to the cell which is located in a cabinet mounted on a wall or skid – not in-line with the pool circulation and filtration system. The cell is where the chlorine reactions are made, after which the chlorine solution flows to a holding tank (oxidant tank) and stored. Once the tank is full the generator will stop producing chlorine and go into a standby mode automatically. The tank has an ultrasonic level sensor that detects the volume level in the tank. As the tank volume decreases the generator will start up automatically and begin producing more chlorine to refill the oxidant tank. The chlorine is simply fed from the oxidant tank to the pool return line via chemical metering pumps or venturi systems as needed from swimmer demand. The oxidant tank is sized for the entire demand of daily consumption, so peak swimming times and moderate swim times can be accommodated without any adjustments to the chlorine generator.
While most pool operators are aware that other types of disinfectants such as ozone and ultraviolet light provide particular benefits, they must be used in conjunction with a chlorinated product or equivalent to provide acceptable pool sanitation. Of the chlorine alternatives, on-site generation of sodium hypochlorite for many aquatic applications is considered an effective and safe treatment option that provides multiple benefits when compared to traditional chlorine-based disinfection methods.
For more information, e-mail info@severntrentservices.com.
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