March 6, 2013

Safe Drinking Water? It’s in the Ozone.

Hi everyone. I’m Rich Baril, product marketing manager at Emerson Process Management. All of us at Rosemount Analytical get very excited about water. Maintaining and improving water quality for municipal, industrial and commercial applications is one of our biggest jobs. Today, I want to talk about a technology being used more and more to maintain drinking water quality – whether at the treatment plant or bottling plant – and that’s ozone.

As you know, many different pathogens (bacteria, viruses and parasitic protozoa), some of which are potentially lethal, can be found in both surface water and some groundwater sources. Disinfection is integral to ensuring water quality and safety. Large-scale use of chlorine for water disinfection began in the U.S. in 1908, and chlorine is now used in both primary and secondary disinfection steps at many water treatment plants. However it has been reported that trihalomethanes and haloacetic acids are produced as byproducts of the chlorination process, and that these byproducts could be hazardous. Ozone also can produce byproducts, bromates, and much study about safe levels is being conducted.

In response to these reports, many water utilities have begun examining alternatives to chlorine for primary water disinfection, two of which are monochloramine and ozone. We will discuss ozone in this blog.

The first drinking water plant began operations in Nice, France in 1906. Since Nice has been using ozone since that time, it generally is referred to as the birthplace of ozonation for drinking water treatment. Today, some U.S. water plants are moving to ozone for disinfection to address more stringent drinking water regulations. Ozone is a powerful oxidant. Its effectiveness is measured by the amount of residual ozone remaining. The presence of a small residual implies that all organic compounds have already been neutralized.

Adding ozone to bottled water is a way to ensure that the water in the bottle is free of microorganisms, without leaving trace disinfectants.  When diffused into water, ozone oxidizes organic material, including waterborne microorganisms. It’s more effective than chemical disinfectants like chlorine and is both odorless and tasteless.  Because of ozone’s short half-life, any bottled ozonated water will have little or no remaining ozone in the solution.  It will have received an effective disinfection prior to bottling which will leave no residual disinfectant.

Ozone gas is produced by electrical discharge in air. The gas is injected into a contact chamber via diffusers to distribute the gas evenly and speed the disinfection process along. The ozone concentration in the contact chamber, where reaction is still occurring, can therefore be much higher than in the final effluent. Some ozone generator manufacturers recommend monitoring ozone concentration in the contact chamber to meet disinfection requirements. Aside from the capital cost of the ozone generator itself, the main cost of an ozone system is the electricity used.

Have you used or considered using ozone for water treatment? What was your experience? We’ll be happy to talk with you about the effective use of ozone in your water treatment or bottling plant – just let us know!

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