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Ozone In The Laundry Industry - A View From Both Sides

Our print copy of LaundryTODAY ran edited pieces on the opposing views of Ozone by  industry professionals Steve Tinker and Jack Reiff. Their full articles are available here.

 

Tinker Viewpoint                         Reiff Viewpoint

Ozone in Laundry – What You Need to Know

By  Steven J. Tinker, Vice President, Research & Development
Gurtler Industries, Inc.

For many years various companies have been promoting the use of ozone in laundry operations as a way to save costs on energy and chemicals, as compared to traditional laundering methods.  The following is a review of ozone technology as it is proposed in a laundry operation and of some of the claims that have been made.  Included at the end is a series of questions you should ask before you consider an ozone system for your laundry.

Background

Oxidation Potential:  Ozone is an oxygen-based compound.  Oxygen is naturally present as a gas that is composed of two oxygen atoms, and represented as O2.  Ozone is composed of three oxygen atoms and designed as O3.  Ozone is a toxic gas, and extremely unstable, as the oxygen prefers to revert to the stable O2 structure.  When ozone is generated, it will quickly revert to the preferred two-atom gas, releasing an extremely active oxidizing atom of oxygen.  This oxidizing potential is the property that is most important in a laundry application. Compared to other oxidizing substances, ozone has a relatively high oxidation potential:

Oxidant 
Oxidation Potential (eV)
Fluorine
3.00
Ozone
2.10
Hydrogen Peroxide
1.80
Potassium Permanganate
1.70
Chlorine Dioxide
1.50
Sodium Hypochlorite
1.40
eV = electron-Volts 

Solubility in Water:  Ozone is sparingly soluble in water. At 20oC, the solubility of 100 percent ozone is only 570 mg/L.  Consequently, typical concentrations of ozone found during water treatment range from <0.1 to 1mg/L, although higher concentrations can be attained under optimum conditions. (Note: 1mg/L ~ 1 ppm; ppm: part(s) per million.)

Sanitation and Disinfection:  Ozone’s oxidation potential is most important when considering its sanitation properties.  Ozone primarily disinfects or sanitizes by destroying bacterial membranes or cell walls. 

Ozone is capable of oxidizing many organic and inorganic compounds in water.  Ozone is a powerful oxidant able to achieve disinfection with less contact time and concentration than all weaker disinfectants, such as chlorine.  However, since ozone dissipates quickly, it cannot maintain a residual in the system and it must be constantly regenerated to be effective. 

Hazards in the Workplace:  Ozone is a toxic gas.  To protect workers potentially exposed to ozone, OSHA has established a permissible exposure limit (PEL) of 0.1 ppm (29 CFR 1910.1000 table Z-1), calculated as an 8 hour time weighted average. Higher concentrations are especially hazardous and

NIOSH has established an Immediately Dangerous to Life and Health Limit (IDLH) of 5 ppm.  Work environments where ozone is used or where it is likely to be produced should have adequate ventilation and it is prudent to have a monitor for ozone that will alarm if the concentration exceeds the OSHA PEL. Continuous monitors for ozone are available from several suppliers.
Even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs. The severity of injury depends on both by the concentration of ozone and the duration of exposure. Severe and permanent lung injury or death could result from even a very short-term exposure to relatively low concentrations.

Ozone in Laundry

Over the last two decades numerous companies have entered the laundry market touting the benefits of on-site ozone generation in the laundry process.  Generally their claims fall into two broad categories:

  • Significant savings can be had by elimination of hot water, as ozone performs very effectively in cold water.
  • Significant savings can be had by reducing chemicals in the wash process, as ozone will clean and sanitize in one step.

Other claims include:

  • Due to lower use of chemicals and less harsh washing conditions, textiles will last longer.
  • Less rinsing is necessary, since lower levels of chemicals are used, thus saving water.
  • Cycle times can be shorter, increasing productivity.
  • Ozone is a deodorizer, and as such can produce “fresher” smelling textiles.

The following is a more in depth evaluation of ozone claims:

Cold water washing:  Most ozone systems generate a few ppm of active ozone constantly during the process, replacing the ozone as it reacts or dissipates.  Ozone will dissipate in a matter of seconds if warm or hot temperatures are used, so ozone use requires cold water washing.  It is theorized that ozone will oxidize soils in the laundry washing operation, reactions that may make the soil molecules more soluble in water, and easier to remove from fabrics.  However, there appears to be no definitive scientific research that will support these claims.

Calculate potential energy savings:  Before you start making radical changes in your wash process, it is important assess how much energy you can save. Determine how many gallons of water you use per month, and then estimate the average temperature decrease you wish to achieve. A gallon of water weighs 8.3 lbs. So if you use 500,000 gallons of water per month, you’ve got 4.15 million lbs. of water. A Btu (British thermal unit) is the amount of energy required to increase the temperature of a pound of water 1ºF. If you decrease your average temperature by 15ºF, you can save 62.25 million Btu per month. One cubic foot of natural gas is equivalent to 1,031 Btu and 1 therm is equal to 100,000 Btu. Check with your natural gas supplier to determine what they charge per ccf (100 cubic feet) or per therm to determine potential savings. Remember that your boiler or water heating system will not be 100% efficient; so adjust your savings accordingly. If your water heater is 80% efficient, then the savings will really be 77.8 million Btu per month.

Consider your drying energy requirements:  An additional concern is that one should not ignore the effects of the wash aisle energy savings on the energy consumption in the rest of the operation. The greatest amount of energy used in a laundry can be in the drying operation. It is a fact of physics that the energy required to evaporate water is as much as 10 times more than the energy required to heat the water 100ºF, from 60º to 160ºF. Here’s the actual relationship: It takes 1 Btu to raise the temperature of 1 lb. of water 1º F. It takes 980 Btu to convert 1 lb. of liquid water at 212º F into steam at 212º F. In other words the energy used to evaporate water can be much greater in the dryer or ironer as compared to heating water in the wash aisle. For example, if you use three gallons of water to process 1 lb. of fabric, that is 25 lbs. of water. If you lower the water temperature by an average of 15ºF, the energy saved in water heating is about 375 Btu per lb. of fabric. If after extraction there is 0.5 lb. of water left in the fabric, you will require 490 Btu just to evaporate the water. This does not even take into consideration the fuel efficiency factors of your boiler or dryers.

There is a strong potential for higher energy costs if your extraction rates are not optimum. You should try to remove as much water from the fabric and textiles as possible during the extract process to reduce the energy required to dry the fabric. That is where the real energy savings can be found. Unfortunately, that’s where you will often observe unintended consequences of changing conditions in the wash aisle.

Cotton fabrics can absorb 2-3 times their weight in water. The extraction process removes most of this absorbed water. Extractors work much more efficiently when the water is warmer. Warmer water has a lower surface tension and will not “cling” to fiber surfaces as much as cold water. Centrifugal extractors are most efficient with cotton when the water temperature is 140ºF. Polyester blends react similarly, but the extraction efficiency levels out at about 120ºF. So, the simple thing to remember is that the final rinse in your facility should always be over 100ºF and is best at 120ºF.

At 120ºF the extraction removes more water from the fabric, requiring significantly less drying energy. Any so-called “low temperature” wash formulas designed to save energy by reducing hot water usage must be adjusted to use warm-to-hot water in the final rinse to improve extraction. Otherwise the energy saved in the boiler will be dwarfed by increased energy requirements in the drying operation. Since drying energy can be the largest energy requirement in your facility, it pays to make sure that your dryers and conditioners are tuned to peak efficiency. Don’t forget to set your drying programs to avoid over drying.

Sanitization:  Since ozone is a sanitizer used in waste and drinking water purification, it is thought that ozone’s sanitation properties can carry over to laundry applications.  However, there are no ozone based products or systems registered by the EPA as sanitizers or disinfectants.  In addition, there are no published reports that evaluate the sanitization efficacy of specific ozone systems that can be found in the scientific literature. 

Long-term soil removal and whiteness retention:  With lower temperature, fatty soils, such as the oils and sebum from skin will be more difficult to remove, as they are lower in liquidity in cold water.  If lightly soiled items are processed through cold water with lowered or eliminated detergent usages, there may not be a visible whiteness decrease after one or two cycles.  However, after 25 or 50 cycles it has been observed that some ozone installations have resulted in a significant increase in graying due to a long term build-up of soils and minerals in the water and the fabrics that ozone hasn’t completely removed. 

One more note, if there is long term graying and soil retention, this can lead to decreased fabric life from soil fabric interaction.  This can especially be a problem if there is added mineral content that will cause harshness (stiffening) and "cutting" of fibers, causing pilling and reduced fabric life.

Open Questions

When considering an ozone system you should ask the prospective supplier and yourself the following questions:

  1. How long has the ozone company been in the laundry business?  How many customers do they have?  Can you get a list of 10 customers that have had their system in place for more than a year? Are you willing to visit a site to judge their quality?
     
  2. What are the projected water and energy savings in Btus and in cost?  Make sure you get their assumptions, and that they agree with your data in the wash and drying operations.
     
  3. Do they have any microbiological testing to demonstrate that the levels of ozone they inject (2-4 ppm) at the temperatures they use (70ºF) have a high degree of efficacy?
     
  4. Do they have quality tests, such as soil removal tests using standard soils such as blood, sebum/dust, or similar soils that they can provide?
     
  5. Have they run long-term whiteness comparisons?
     
  6. Are there any tests that show bleaching efficacy, as to stain removal?
     
  7. Do they have data on drying efficacy at the low temperatures in the final rinse?  

The answers to these questions will help you make an informed decision as to the suitability of ozone in your laundry operation.

Steven J. Tinker has been with Gurtler Industries, Inc. since early 2002 and is currently the Vice President of Research & Development. Gurtler is a national manufacturer of institutional and industrial laundry detergents and processing chemicals. Steve has over 35 years experience in the professional laundry industry as a product development scientist and marketing executive. Steve is one of the founding members of the Board of Directors of the Healthcare Laundry Accreditation Council (HLAC) and has served as the Vice Chairman of the organization, he currently is the Chair of the HLAC Advisory Committee. He is currently the President of the American Reusable Textile Association (ARTA), an organization dedicated to developing the appreciation of reusable textiles over disposables. Steve currently serves on the Healthcare Committee of TRSA, the Textile Rental Services Association.


Better Things for Better Living Through Chemistry OR The Practical side of using ozone in The Laundry

By Jack J. Reiff President,
WET-TECH, The Ozone People

The laundering process as we know of and practice today, is chemically intensive and quite complicated. We are using an alkali for saponification and emulsification of soil. The alkali is usually a sodium Hydroxide or potassium Hydroxide chemical (Caustic Soda) that is quite aggressive and detrimental to your health. The detergent or soap used for lubrication and suspension of soil is synthesized from animal fats (soap) or petroleum by products (Detergents) which can cause some problems when inhaled or in contact with a person’s skin. We know of the use and dangers of chlorine, a standard product used for sanitizing and whitening of fabric. (Chlorine gas, is very problematic to humans. We then move on to an anti-chlor to chemically react with chlorine along with other treatment chemicals. These consist of fabric softeners, (natural or synthetic) sours, (mild acids) and other treatments considered important to maintain a disinfected or sanitized product. Most if not all of these products consume oxygen when used in the washing process to convert, react or change the soils encountered. This consumption of oxygen also impacts heavily on your waste water stream creating a need for other chemical applications to control the levels of contamination. We have learned to use these products safely and effectively so that they are not a major concern to washroom operators.

Ozone is a chemical of High Oxidation qualities, in a gaseous state, has been around for a long time. I have been told that it has been in use since the late 1800’s. Its qualities in destroying organic matter as well as Bacterial organisms, has made ozone a desirable chemical for use in treating drinking water as well as destroying air borne contaminants. In the early days of the use of ozone, the cost of manufacture limited the areas of application to the few that could afford it. The fact that ozone is an unstable Chemical in a gaseous state that reverts back to oxygen provides a chemical uniqueness especially for the water and linen processing industries. (Like most Chemicals when used and abused, they are potentially hazardous) ie: one or two aspirins can get rid of a headache, many more aspirins can give you more than a headache.

The use of Ozone in a laundry application can be paralleled to a procedure of hanging pictures on a wall. An overly large Hammer will destroy the nail rather than implant it in the wall while a very small jeweler’s hammer will not even get the nail started. So it is with the use of ozone. It does not take a high concentration or high volumes of ozone to correctly impact on the soil in any laundering classification. Throwing a pail of paint at a fence only covers a specific small area but brushing the paint on evenly and consistently will do the right job.

The ORP (Oxidation Reduction Potential) a method of measuring the oxidation strength of Ozone is used most prevalently in the application of ozone in the laundry. Although the level of Ozone is necessary for the destruction of Organic and molecular materials, a high concentration can lead to a false sense of security. The Oxidation Reduction Potential is read by an electric charge being sensed through a glass bulb immersed in the liquid medium. If two ORP sensors are not used in tandem, one for the medium without the Ozone to verify the base level, and one for the medium in to which the ozone is infused, (the test medium), there is a false level of Ozone being read in the test medium. Since ozone has a very short life it becomes important to maintain a specific use level of ozone in the wash liquor so that the entire load can be infused with Ozone throughout the entire wash. The Oxidation qualities of ozone in destroying or reducing the levels of organic materials helps the wash process along by reducing contaminant levels in the wash liquor and assisting in the rinsing process. You can see the soil levels go down by viewing through the front door glass of any wash machine. The knowledge that Ozone destroys or impacts quite heavily on the effects of Chlorine Bleach suggests that ozone should not be used in conjunction with a Chlorine Bleach operation. This brings up some other points of the application of ozone in the wash.

For many years and up to the present, many people have used a Venturi vacuum injector to infuse ozone in to the wash liquor or Ozonated water storage tank. It is a known fact that a vacuum has a very adverse affect on any gas. No one to this date has been able to justify the use of a Venturi Vacuum injector in the application of Ozone. No one to this date has shown any technical test results that indicate that there is no change in this method of introducing ozone in to the wash liquor. To me this means that the level of ozone being infused in to the injector is not the level of ozone that is coming out with the water flow. If we lose ozone value, what becomes enough or too much ozone in this type of application? Yes, in waste water treatment it may not matter but when dealing with textiles that can be oxidized, weakened and perhaps destroyed with heavy doses of ozone it seems apparent that we minimize our levels and maximize our use application. This practice will improve on wash quality, extend linen life, destroy contaminating bacteria and eliminate Toxic off gassing.

There also is the matter that is also talked about - “dissolved ozone” in the water. We have heard many times that the ozone must be solubilized in to the water to make it more effective in its use. There is an energy loss when working to get the Ozone solubilized so that you can then infuse the Ozonated water in to the wash liquor so that the ozone can break away and attack the soil or bacteria contaminants in the wash. In a storage tank it means that the water and the ozone must be rotated and mixed to effect the solubilization. The wash water is a vehicle for moving the ozone to the soil and fabric. If the ozone is emulsified or solubilized in the water it will not be any more available than if it is directly infused in to the water, and at a lower energy cost.

This leads us to the methods we have practiced for many years. We use a very small bubble diffuser that injects the ozone directly in to the water at the wash machine sump, after the wash machine has reached its operating water level. In this way we minimize any off gassing and we get maximum distribution of the ozone in the wash liquor. The ozone levels are sufficient to do the job but not at a high concentration to promote off gassing, fabric damage or equipment wear. The small ozone bubbles are consumed quite readily, doing the job of oxidation while our continuous infusion maintains an ozone level to be consistent in its purpose.

All too often we get mixed up and confused by technical jargon that does not improve on practical applications of products. The chemical industry will have us believe that they have the answer, and that they may. Why some chemical manufacturers ignore the fact that ozone is also a chemical and has some very practical uses within the field of chemistry that should not exclude the use of ozone where it can do a better job. Some chemical manufacturers would rather we use a built sanitizer or disinfectant in the treatment cycle of the wash rather than use an application of ozone. Ozone , through a process called “Cell Lysing” destroys bacteria membranes providing a disinfecting quality where an active cell can not reproduce itself and continue growing. The differences are that a formulated chemical product when used as a disinfectant remains in the fabric after the wash and through the drying process. These products can become activated again when a patient or hotel guest is resting on the sheets or pillow case on a hot day and starts to perspire. The perspiration can resolubilize the chemicals that are intended to remain in the fabric causing an irritation or bed sores. When Ozone is used in the treatment operation it reverts back to oxygen and dissipates after it has sanitized the fabric.
Both methods use chemistry to accomplish the task.

When it comes to other benefits that ozone might offer in the wash cycle you can consider some of the following issues. Ozone helps to soften water to some degree it also makes the water somewhat slicker which helps in the extraction process. The greater the extraction of water from your linen the faster the dry cycle which in many cases saves raw gas going up the exhaust. Ozone counteracts the use of chlorine bleach thereby acting as an anti-chlor reducing or eliminating a chlorine residue on synthetic materials. This helps to maintain a whiteness in the final washed item after drying because the chlorine that is retained by the synthetic fabric is no longer in resident to decompose and turn your laundry a dingy grey. This same quality affects your ironer ribbons and covers because the residual chlorine that is normally transferred to them from the ironed line is no longer in resident so the ribbons and pads will last longer. The other quality of ozone is that it acts very similar to Hydrogen Peroxide in working as a non-chlorinated bleach that will flash off when exposed to heat creating a whitening effect on the linen.
The oxygen qualities of ozone when used in the wash cycle also infuses extra oxygen in to the waste water stream aiding in reducing COD (Chemical Oxygen Demand) BOD, (Bio-Chemical oxygen demand
Along with FOG (Fats oil & grease).

Ozone is not the magic bullet that it was suggested to be many years ago, but the proper application of ozone in the laundering process can provide many benefits. Washing at lower temperatures saves fuel cost, washing with less water and fewer cycles saves on water and sewer charges, using a chemical that enhances other chemicals that you manufacture on site reduces out of pocket chemical costs and washing with shorter cycles saves on productive labor and maintenance costs. All in all, the environmental and monetary benefits become quite large, not to mention green house gas reduction, an EPA hot button.

The CDC has many articles pertaining to the useful benefits of ozone applications in water use and in the laundering process. It is important to do due diligence when searching for an ozone system for your laundry. You can have a short term low cost or a long term low cost. You are in control don’t give it away.

Jack Reiff is the president and principal of WET-TECH, The Ozone People. He is a graduate of Worcester State University with a BS degree in management and a minor in Engineering. Jack has worked as a design engineer with two avionics companies as well as a design engineer at Brookhaven National Laboratories dealing with Nuclear research. With over 50 years of experience in the textile care industry both as an owner of a Laundry Drycleaning plant and as a regional sales manager for Diamond Alkali, Jack has participated in many industry organizations. Jack and WET-TECH have been associated with TCATA, ALM, NELA, NEFA and TRSA, among others. As a member of the TRSA Government affairs and legislative committee, Jack authored the TRSA “OSHA HANDBOOK“ for compliance. Jack has authored many technical articles for industry information and helped to develop private label Laundry Chemicals for several industry manufacturers.

Quick Rinse - News From Around The World

Laundry to Reduce Air Emmissions and Fund Cleaner Burning Wood Stove Purchases

BOSTON, Mass. — Alltex Uniform Rental Service, an industrial laundry in Manchester, N.H. has agreed to settle claims by the US Environmental Protection Agency that it violated the Clean Air Act by paying a civil penalty of $65,000. They will also be undertaking a Supplemental Environmental Project with a value of at least $220,000 to replace old, polluting wood stoves in southern New Hampshire with new, cleaner models. Additionally, the company will install equipment at its facility to remove approximately 20 tons per year of emissions of volatile organic compounds (“VOCs”). G&K Services is the parent company of Alltex Uniform Rental Service Inc. The EPA action grew out of an EPA inspection of the facility in July 2008.