Mixed Oxidants show disinfection benefits for municipalities

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Courtesy of MIOX Corporation

“The most significant advantage over gas chlorination or hypochlorination is an ability to maintain chlorine residuals further along the water distribution system, due to better biofilm removal. Other noted advantages of mixed oxidants are ease of operation with self-cleaning electrolytic cell on-site generators, fewer safety issues in comparison to gas chlorination, and lower costs compared to purchasing hypochlorite in bulk.”

Municipalities in Canada have been using mixed oxidant chemistry on a trial basis and have found that mixed oxidants are a viable alternative to gas and hypochlorite disinfection.

The most significant advantage over gas chlorination or hypochlorination is an ability to maintain chlorine residuals further along the water distribution system, due to better biofilm removal. Other noted advantages of mixed oxidants are ease of operation with self-cleaning electrolytic cell on-site generators, fewer safety issues in comparison to gas chlorination, and lower costs compared to purchasing hypochlorite in bulk.

For compliance with provincial requirements, the mixed oxidant solution is measured and dosed as free available chlorine (FAC) and therefore the same
disinfection requirements for gas chlorination and hypochlorination will apply.

How on-site generators work
While many different types of on-site generators (OSG) are available, there are a number of components that almost every OSG uses (see Figure 1).
Water coming into the OSG first goes through a softener, after which it is split into two lines. One line feeds directly into the electrolytic cell, while the other is used to fill the brine tank. The brine tank stores a concentrated salt solution, prepared by having an excess of salt in the tank so that the solution is near-saturated brine. It is then injected into the softened water stream entering the electrolytic cell.

When the dilute salt solution is inside the electrochemical cell, a current is passed through the cell, producing the oxidant (sodium hypochlorite or other oxidants) solution. After leaving the electrolytic cell, the oxidant solution is stored temporarily in the oxidant tank and is then metered into the water moving through the treatment process. Hydrogen gas is also produced inside the electrolytic cell, and the hydrogen is removed from the cell and oxidant storage tank through vents.

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