About ozone

Ozone in the Laundry Industry --

Practical Experiences in the United Kingdom

Dick Cardis¹, Cameron Tapp², Marc DeBrum², and Rip G. Rice³

¹ JLA Limited, Meadowcroft Lane, Ripponden, West Yorkshire HX6 4AL, UK dcardis@jla.com

² ClearWater Tech, Inc., 850 #E. Capitolio Way, San Luis Obispo, CA 93401, USA ctapp@cwtozone.com; mdebrum@cwtozone.com

³ RICE International Consulting Enterprises,

1710 Hickory Knoll Road, Sandy Spring, MD 20860 RGRice4ozone@aol.com

Abstract

Since the early 1990s, the use of ozone in many commercial and industrial laundering applications has been evolving rapidly. Ozone allows washing to be conducted using cold water, thereby saving considerable heat energy and water consumption. Additionally, ozone enhances the wash process, resulting in a significant reduction in detergent dosage and number of rinses, thus saving water. Ozone/cold water cycles are gentler to fabrics, thus extending linen life. Finally, ozone/cold water laundering is beneficial for effluents, resulting in reductions in COD (chemical oxygen demand). Microorganisms are destroyed effectively in ozone-wash waters, and washing and drying cycles are shorter, thus saving labor.

In this paper, the authors describe some specific case studies at commercial laundering installations in the UK, whereby the users of ozone have reaped major benefits, including enhanced microorganism kills/inactivation and significant cost savings.

Keywords

Ozone, Laundries, Bacteria Kills, Virus Inactivation, Economic Benefits, Clostridium difficile, MSRA,

Introduction (ClearWater Tech, 2003, 2006)

Over the years, commercial laundry operations have improved by achieving higher per-load capacities and automated cycle and chemical management to ensure consistent quality over many loads. These improvements are notable, yet many financial and regulatory pressures continue to face commercial laundering, including:

o Water consumption and conservation

o Energy conservation

o Waste products management

o Efficiency per laundry load

o Fabric lifetime cost

These issues apply in all commercial laundry settings, ranging from hospitals and institutional care to hospitality installations and for-profit commercial laundries.

The number of commercial laundering facilities in the United States alone was estimated in 2003 at 140,400, categorized in Table 1 (ClearWater Tech, 2003).

Table 1. U.S. Commercial Laundering Facilities (ClearWater Tech, 2003)

Category	Laundry Facilities
Hospitals	7,400
Nursing homes	39,700
Hotels and Motels	47,000
Prisons	4,200
Commercial Laundries	7,100
Coin Operated Laundries	35,000

Starting in the mid-to-late 1980s, work began to determine if ozone, O₃, a known powerful oxidant and disinfectant, would allow laundering to be performed using ambient temperature water. The strong oxidizing and bleaching properties of ozone might allow reduction or even elimination of laundering detergents, thus lowering the chemical loads in discharge wastewaters. Simultaneously, ozone’s strong disinfecting capabilities might also kill or inactivate problematic microorganisms found in many soiled textiles, e.g., from hospitals, medical facilities, nursing homes, etc.

Two remarkable properties of ozone stand out in its application to laundry systems :

1. because it leaves no chemical residue and because the amount of detergent needed with ozone treatment is much lower, ozone-sanitized wash needs far less rinsing, saving water, and

2. because ozone works so efficiently in cold water, sanitizing as well as cleaning can be done in cold water, saving energy.

With less rinsing, wash loads can be completed faster, thus utilizing the laundry equipment more efficiently and reducing the total staff hours per load.

Ozone,s arrival for commercial laundries has proceeded on a normal innovation-adoption path. Ozone-based commercial laundries currently are operating in all segments of the commercial laundry market, in many places round the globe, with some in continuous operation for ten years or more.

Objectives of This Paper

In the United Kingdom, rapid and significant advances in developing the application of ozone in commercial laundries have been made in recent years. A leader in this effort has been JLA, Limited, of Ripponden, West Yorkshire, who has been into the ozone-laundry business since mid-2004. The primary purpose of this paper is to document results from studies conducted by

independent microbiological laboratories and other organizations to document the various aspects of ozone’s application in commercial laundering equipment. Another objective is to document and quantify the cost savings obtainable by utilizing this revolutionary technology in commercial laundries.

Ozone (Cold Water) Washing (ClearWater Tech, 2003, 2006)

When designing a commercial laundering system incorporating ozone and/or when retrofitting ozone system into existing commercial laundering systems, there are three fundamentally different design approaches in use.

! Recirculation Injection – This design can handle the heaviest demands and saves the most water, energy and time. The break cycle uses conventional laundry methods with hot - warm water and chemicals. However, that’s where conventional processes end. All other chemical cycles are replaced with cold water and low and at times no chemical injection. The rinse water is continually cycled back to the ozone system for extreme oxidation of the rinse water and a predetermined amount of dissolved ozone is sent back to the washer for sanitizing of the laundry.

! Direct Water Injection – Ozone is introduced directly by injection to the cold water supply line. This approach allows for effective concentrations of ozone for disinfection and odor control in any cold water cycle. This method offers good effectiveness with good return on investment through savings in chemicals and energy. A variation on this approach includes a contact tank in which ozone is mixed with cold water and stored until needed by the wash cycle. The contact tank approach makes it possible to achieve higher effective concentrations of ozone.

! Air Injection – Ozone gas is injected directly into the catch basin of the washer. A properly designed air injection system will activate traditional laundry detergents, allowing them to do their job with less water and at lower temperature. In this approach, ozone is relied on for disinfection and overall laundry quality with reduced costs. Disinfection is achieved with the ozone gas in solution as well as linen folding into the ambient ozone in the wash drum. An ambient air ozone monitor within the facility and/or within the wash drum will control ozone off-gas and eliminate any concerns of high ozone levels in the laundry facility. However, if applied correctly the air injection method of ozonating a commercial or institutional laundry will yield the highest return on investment of the three basic designs.

Figure 1 (California Urban Water Conservation Council, 2006) shows a schematic diagram of a direct injection laundry system with holding tank, (three washing machines) using ozone. This figure shows the optional installation of a Granular Activated Carbon filter to treat incoming municipal water.

Figure 2 (ClearWaterTech, 2006) shows more details of the air injection ozone equipment for a single washing machine (Figure 2a) and Figure 2b shows the same details for two washing

machines fitted with a single ozone air injection system. The oxygen concentrator removes some of the nitrogen from ambient air, thereby concentrating the oxygen to levels above 90% by weight. Higher oxygen concentrations in the feed gas to ozone generators result in higher ozone concentrations being produced. The ambient ozone controller monitors ozone in the ambient air. Should the level of ambient ozone ever exceed local regulations, this controller automatically shuts off the ozone generator until the source of the ambient ozone can be found and repaired. The gaseous ozone produced by the generator is fed via a diffuser into water entering the washer. The ozone system turns on during any “step” within the wash formula via a “dry contact” (no voltage) signal or 120-240V AC signal to the main control board of the ozone generator.

Figure 1. Ozone laundry systems (California Urban Water Conservation Council, 2006).

Other LED units on the display panel indicate other functions of the equipment. Thus the operational status of this equipment can be checked and monitored visually by personnel responsible for laundering without requiring detailed technical training.

The ozone output for any given wash load can be increased or decreased by turning a potentiometer or manual ozone output control knob located on the control panel of the ozone generator. As this potentiometer is turned clockwise, the LED bars illuminate one at a time. In this manner, the proper amount of ozone is applied to cope with the kind/type of soils on articles placed in the washer. The ozone output also can be varied by changing the flow rate of air entering the ozone generator.

Figures 2a,b. Schematic drawings of two CWT ECOTEX™ ozone laundry systems (ClearWater Tech, 2006).

The OTEX Ozone Washing System and Process

This process and complete laundering system is offered on a fixed-price rental basis, including full maintenance, in the United Kingdom by JLA, Ltd. The firm has been monitoring ozone technology since 1995, and developing and perfecting an ozone laundering system since 2002. Commercial ozone-laundering systems were introduced in 2004.

OTEX washing equipment ranges in size to allow laundering of from 16 lbs to 126 lbs, and each equipment component complies fully with all relevant UK water and health regulations. Materials of construction are resistant to ozone-containing gases and waters. Dryers handle capacities of from 20 lbs to 179 lbs, and include the S.A.F.E. (Sensor Activated Fire Extinguishing) system for dryers. Typically, the equipment installer sets the ozone output control knob for the desired ozone output for the degree(s) of soil likely to be encountered on linens at the facility. Personnel doing the laundering then only need choose the program number 1 through 4 (1 being for the heaviest soil and 4 for the lightest), then push “start”.

Liquid detergent and other chemicals are injected according to measured doses into the wash cycle using peristaltic pumps supplied by detergent companies. Detergent control is important in ozone laundering because indiscriminate addition of more detergent than is needed will use up the ozone and will require more-than-necessary rinsing.

A proprietary ozone/water contacting system (the interfusor) is employed that creates a vortex effect, enabling more ozone to be dissolved in a given volume of water than by standard ozone contacting methods. In turn, this allows a higher degree of microorganism kills without producing excessive amounts of ozone off-gas.

An additional feature of the OTEX ozone laundry systems is the inclusion of a means to vary the amount of ozone fed to any wash water. As with household clothing and linens, some soils are heavy (oils, greases, mud, etc.) while other soils are light (personal garments). Heavier soils require more ozone than do light soils. Consequently, the OTEX display board contains a sequence of ten LED (Light Emitting Diode) bars, which indicate 0 to 100% of the ozone output available from the ozonation equipment installed. Each LED bar indicates an additional 10% of the ozone output available above the preceding LED bar.

The OTEX single reaction chamber ozone generator produces 4 g of ozone per hour at 3% ozone concentration in the gas phase at a gas flow rate of 4 scfh at 100% output (LED bar #10 illuminated). At a gas flow rate of 3 scfh, this same unit produces 3.1 g/h of ozone at 3.2% ozone concentration in the gas phase at 100% output. At 60% output (6^th LED bar illuminated), this unit produces 1.86 g/h of ozone at 1.92% concentration in the gas phase at 3 scfh.

Advantages of Ozone in Commercial Laundering Systems

(ClearWater Tech, 2006)

! Reduces Energy Use – Ozone enhances the effectiveness of the actions of chemicals, reducing the need for high temperature washing. Estimates of savings potential are as high as 90% in washing and 20% in drying. The Magnolia Manor, an assisted-living facility in Americus, GA (USA) has documented energy savings of 51.3%.

! Reduces Water Use – Ozone wash systems normally require fewer rinse steps, thus reducing water usage by an estimated 30-45%. Closed loop systems are more expensive but recover most of the water, so that reductions in water use can reach 70-75%.

! Reduces Chemical Use – Ozone makes existing chemicals work better, and reduces overall chemical demand in several ways:

! Ozone helps supply oxygen to the wash water, which increases chemical effectiveness and reduces chemical demand.

! Ozone oxidizes linen soils, making them easier to remove from the wash water.

! Ozone can reduce the need for harsh, high-pH chemicals traditionally used to remove Fats, Oils and Grease (FOG) by breaking some of the molecular bonds in FOG and reducing them to simpler carbon compounds. While virtually all ozone laundry systems use at least some chemicals, savings claims range from 25% to 70%. Actual savings will depend on the type of laundry being washed, the temperature and hardness of supply water and the design of the system.

! Ozone in water solution performs the function of chlorine bleach, without producing byproducts. Ozone works quite well and safely in conjunction with hydrogen peroxide if a separate bleach cycle is desired. Also, because ozone improves the removal of soils from wash water, it helps prevent redeposition of soil onto the wash (one of the major causes of fabric graying) which in turn reduces the need for bleaching.

! Purifies and Disinfects – Ozone is very effective against bacteria, viruses and other microorganisms. The key is achieving a “CT” value (contact time in minutes multiplied by ozone concentration in mg/L) of 1 mg/L-min or more.

! Improves Textile Life and Quality – Shorter cycle times and cooler temperature water (because fewer rinse steps are required) means less wear and tear on textiles. Also, reduced exposure to chemicals can improve fabric life. Additionally, ozone assists in water softening by removing hardeners such as calcium and magnesium from the water. This occurs by the complex mechanism of ozone adding oxygen moieties to some of the partially oxidized organic materials presents in laundry soils. The oxygenated organic laundry soils can form insoluble complexes with polyvalent cations (Ca, Mg, Fe, etc.), thereby softening the ozone-treated laundry waters. Softer water produces a better feel in washed fabrics due to better sudsing and more complete rinsing action. Finally, ozone is an effective deodorizer that works by breaking molecular bonds of many organic and inorganic compounds typically responsible for odors.

! Improves Effluent Quality – Effluent surcharges can be reduced because ozone oxidizes bacteria, other microorganisms, and some dissolved organic compounds that make up biochemical oxygen demand (BOD). Also, because fewer chemicals are used in ozone laundry systems, chemical oxygen demand (COD) may be reduced as well.

These benefits will be quantified in later sections of this paper.

Special Testing Conducted for this Paper

Many test studies were conducted during 2004-2005 in the United Kingdom to determine particular effects and efficacy of ozone in commercial laundering systems. Several representative studies will be described below.

MICROBIOLOGICAL TESTING

Test #1. Comparison of Hot Water (75-80/C) to OTEX Laundering Process vs C. difficile spores (Microsearch Labs., May 15, 2004)

A laboratory test was conducted by Microsearch Laboratories Ltd. comparing the effects of hot water (75/ and 80/C) over 15 minutes to 2.5-minutes laundering using cold water in the OTEX ozone-laundering process on Clostridium difficile spores. C. difficile is an intestinal bacterium that causes hospital-acquired diarrhoea. In elderly patients, this can result in serious illness, and even death. The bacterium produces toxins which damage the cells lining the bowel. C. difficile survives well outside the body because it is a spore-forming microorganism.

Data are presented in Figures 3 (hot water results) and 4 (OTEX results). Hot water testing was conducted at 75/C over 15 minutes, and at 80/C over 15 minutes. The reduction in levels of C. difficile spores was insignificant (Figure 3). Figure 4 shows data obtained from OTEX ozone laundry water at ambient temperature (cold water). Even after only 2.5 minutes, no viable trace of spores could be found.