Mass Transfer – Dissolving Ozone Gas Into Water

For ozone to be useful in cleaning and sanitizing linen and other washables, it must be dissolved in the water used to wash the linen. Dissolving ozone gas into solution is called ‘Mass Transfer’. Ozone gas, like just about everything else, can be dissolved in water. Fish breathe oxygen that is dissolved in the water. If there was no oxygen dissolved in the water, the fish would suffocate. Your soda-pop fizzes because the carbon dioxide gas that is dissolved in the liquid is coming out of solution. Ozone gas can be put into solution only if you know how to do it.

You must address several critical variables to achieve the level of success you desire.

  • Contact Time (CT) between the bubbles of ozone and the water
  • Ozone concentration in the feed gas is extremely important to achieve full cleaning power
  • Small bubble size increases the surface area of ozone gas in contact with the water
  • Pressure exerted on the bubbles of gas in the water greatly enhances mass transfer
  • Temperature is extremely important – heat is ozone’s worst enemy
  • pH must not be too low or ozone will immediately off-gas (come out of solution)
  • Proper mixing is required to thoroughly distribute the dissolved ozone in the wash water
  • Containment of the ozone gas at all times is critical to the safety of the laundry staff

Contact or dwell Time – the longer bubbles of ozone gas are in contact with the water column, the more ozone gas you get dissolved into solution. If you want to dissolve something in water, the longer you leave it in the water, the more of it is going to be dissolved. Contact time is the MOST critical variable!

Ozone Concentration – The concentration of ozone in the feed gas is directly related to the quality of the equipment used to generate it. The higher the concentration of ozone, the more of it you are going to get into solution. Some equipment only produces from 1% to 3% ozone by weight. Water Energy ozone generators produce a full 12% ozone concentration by weight. That is the top of the scale of what modern, advanced ozone generators are able to produce

Surface Area – The smaller the bubbles are, the more surface area of ozone is in contact with the water column. Water Energy uses a Static Mixer to chop up bubbles of ozone into millions of ultra-tiny bubbles with an amazing amount of surface area in contact with the water

Pressure is critical to making it all work extremely well. When you exert pressure on the water/gas mixture, the bubbles are literally forced into solution. When bubbles of ozone are contained within the water column and pressure is exerted on that mixture, the water presses on all sides of the bubbles and facilitates rapid mass transfer of the gas into solution. Tiny bubbles simply vanish. They are instantly dissolved and become part of the liquid medium. This is why Water Energy uses a Contact Tank where city water pressure is used to pressurize the gas/water mixture and exponentially increase the amount of ozone that gets dissolved and becomes liquid phase ozone

Temperature – ozone WILL NOT dissolve into water that is above 95-degrees Fahrenheit! Heat is ozone’s worst enemy! You must eliminate as much heat as possible from the wash wheel to achieve the greatest success with ozone

pH – the pH in the wash wheel is important for ozone success. A low pH will cause the ozone to off-gas and come out of solution immediately. Therefore, neutral to slightly alkaline pH is highly recommended. Too much alkali (too high of a pH) with ozone will cause yellowing of your linen

Proper Mixing – there must be significant and substantial mixing of the water and ozone to ensure all of the water has ample ozone to achieve superior results and to prevent any ‘Hot Spots’ of concentrated ozone that can damage your equipment and your linen. This Quality Assurance step ensures that water coming into contact with any bacteria, mold, virus, stain, odor, chemical, etc. will contain sufficient ozone to inactivate the unwanted item

Containment of all ozone gas within the system, at all times, is required to achieve the highest safety margins for an ozone exposure hazard. Water Energy Ozone Laundry Systems are completely sealed. We incorporate a stainless steel reaction tank where ozone gas and water mix together. Any remaining gas rises to the top of the tank and is vented to the exterior of the building. All ozone within any washer is in liquid phase and is dissolved in solution. The Government, OSHA, declares that ozone ceases to be recognized as a concern once it is dissolved in water. Meaning: There is no exposure hazard for ozone that is dissolved in water

There are other variables that must be addressed to achieve superior results but these are the most critical to achieve truly measureable and reliable results. Water Energy ozone systems address all of these variables and several others that we have learned in our 30+ years of R&D with liquid-phase ozone applications.