History in the Making
The bottled water industry is maturing and, like wine, has gotten better with age. Major changes have taken place over the years, from the way the product is processed, to the materials used to contain the finished product. Old methods have been replaced with new and more efficient processes, but one thing has not changed—the need for safe, efficient and affordable sanitation. That is where ozone comes in.
Ozone has played a major role in the history and development of the bottled water industry, and one of the biggest changes in the bottling of water has been the bottle itself. In the early 1970s, bottlers began to slowly transition from glass to plastic containers, especially in the 5-gal home/office delivery market. This change in materials was very good for the industry, but as often happens in business, the law of unintended consequences came into play.
Adapting to Change
In the past, the standard procedure for sanitizing a glass bottle was to spray or dip the bottles in a 2% solution of hot caustic and then thoroughly rinse. The caustic solution cleaned and sanitized the bottles effectively, but the glass needed to be slowly raised in temperature to accommodate the hot caustic and slowly lowered in temperature during the rinse, so the glass would not shatter. The plastic bottle was a big improvement over glass because of the increased durability and lower cost. What was then unforeseen, however, was the way plastic bottles reacted to the standard sanitation methods of the day.
The new plastic bottles did not like to be bathed in hot caustic and made it known over a relatively short period of time. Plastic bottles treated in the traditional way (with hot caustic) started to fade, crack and leak. This incompatibility between current sanitation methods and new materials created quite a problem until some bottlers decided to use ozone to clean and wash their plastic bottles. As the product water was already being sanitized with ozone, it was a logical step to adapt its use to bottle sanitation as well.
Ozone proved to be highly effective as a bottle-washing agent, not only for plastic bottles but for glass as well. In addition to the savings realized by switching from plastic to glass, bottlers switching to ozone for washing also saw huge energy savings because ozone works best in cold water. Now, water bottlers could use ozone for sanitizing both the product water and the containers holding it.
This was a history-making combination that benefited consumers and bottlers alike. The consumers received a cleaner, healthier product, and bottlers received increased profits through reduced expenses—a true win-win situation.
To give a little background on how ozone works, it must first be understood that ozone is a gas that can be infused and dissolved into water. Dissolve a little ozone into water, and the water is sanitized; dissolve a lot of ozone into water, and the water itself becomes a sanitizer. Ozone really is that simple to understand. Where it gets a little more complicated is determining how much ozone is enough and how much ozone is too much.
Enough ozone to sanitize the product water may not be enough to sanitize and wash the bottles. Enough ozone to wash and sanitize the bottle may, in some cases, be too much ozone for the product water, such as in the case of spring water sources with bromide and complying with E.U. standards that prohibit additives of any kind, if product water is labeled “Spring or Artesian sources.”
This quandary ushered in the development of the dissolved ozone monitor. This single development has had a profound effect on the bottled water industry. With the advent of this new technological advancement, it was possible to take full advantage of the power of ozone. Getting ozone dissolved into water can be achieved in a number of ways; each method has advantages and disadvantages, but as with water bottling, many things have changed over the years.
In the early days of sanitizing water for bottling, ozone was dissolved into product water by using large bubbler tanks to allow small ozone bubbles to rise through the water and dissolve into the water on the way up. These diffusion towers were often as large as 15 to 20 ft tall and 3 to 6 ft in diameter. The contact time or CT value was calculated by how much time it took for the ozone gas to travel to the top of the tower. This method is still in use today, but it has long since given way to newer and more efficient ways of dissolving ozone into water.
Two of today’s most efficient ways of dissolving ozone into water are through the use of venturi injection and counter current absorption techniques. Venturi injection is very simple and is based on Bernoulli’s principle, the same law of nature that allows airplanes to fly. When the flow of air or liquid is constricted by a necked down area or portion of tube, called a venturi, the velocity of the air or liquid in that section must increase, and the pressure, relative to the atmosphere, must go down. This lower pressure is termed a vacuum; it is this created vacuum that literally pulls the ozone gas into the passing fluid, where it is mixed and dissolved.
Another way to dissolve ozone into water is through a gas scrubbing process also seen in smoke stack design. This is a simple process that cascades water down through a stainless steel column filled with specially designed media, while ozone gas is pumped in from the bottom. This counter current of gas and fluid allows for the mass transfer of ozone into the water where it then dissolves.
Whichever method is used to dissolve ozone into water, it is thanks to the dissolved ozone monitor and the ozone generators that take advantage of its readings, which have allowed bottlers to take full advantage of what ozone has to offer.