Low temperature washing for healthcare

Energy remains a significant component of wash costs. Many launderers are looking to reduce this and other costs through increased productivity and efficiency. The laundry the latest laundry chemical technology has been geared to reduced temperature washing however, this has largely been utilised by those launderers specialising in hospitality markets, whilsethe healthcare launderer is still predominantly relying on high temperature wash processes. Indeed, it was only with the introduction of EN14065 in 2005 that the door was opened to the use of novel technology to ensure disinfection in healthcare. This meant that lower temperature processing is now on the table for the healthcare launderer instead of the traditional HSG 95/18 guidance of 71C for three minutes for cotton, 65C for 10 minutes for polyester and polycotton blends or the appropriate use of sodium hypochlorite.

In the on-premise social care marketplace the adoption of low temperature washing was pioneered by the laundry equipment suppliers and the use of ozone became commonplace.

Therefore, the early move by the industrial laundries towards the possibility of adopting lower wash temperatures in healthcare, was closely geared to the adoption of EN14065. The private sector led the way and being certified with a system that meets the requirements of EN 14065:2005 (now EN 14065:20016) has now become a de facto passport to entry into the laundering and textile rental healthcare market. So, healthcare launderers in the UK entered the energy crisis with modern legislation and the latest chemistry already in place.

Reasons for high temperature washing

Implied thermal disinfection was developed and widely publicised by the International Technical Committee on Laundering (ISTCL) and many others in the period 1970 to 2000. It was found as the result of many studies in several countries, particularly in Europe, that a large proportion of the pathogens on soiled healthcare textiles were destroyed if the wash process incorporated a period in the wash liquor of at least 3 minutes above 71C. (The exceptions included spore-formers such Bacillus cereus and Clostridium difficile, but these were dealt with separately.) It was therefore assumed that simply by ensuring that if the necessary temperature was achieved in the wash process, disinfection would be adequate for multiple re-use of the laundered textiles. There was no ongoing requirement for regular checks that this was actually being achieved. Occasional checks were carried out by LTC in the UK and others overseas, and these sometimes did reveal poor disinfection. The reasons for this were usually apparent (overloading of a washer extractor was a common one, because the middle of the load never got as hot as the temperature sensor in the sump).

Traditionally the high temperature hospital laundering process also relied on high alkalinity and good mechanical action to emulsify the fatty proteins in human body fluids. The hot water promoted swelling of the cotton yarns to aid release of ointments and solid particles.

Detergent development

Meanwhile, detergent chemists were tackling the problems of low temperature chemical disinfection in healthcare wash processes. They developed a range of options and the all-important testing protocols to ensure that they actually delivered effective disinfection long-term. They had to meet the NHS requirement for a 5log10 reduction in bacteria (effectively a 100,000-fold reduction) with no mutations into species that could survive multiple washing. They also had to ensure the effective physical removal of sporeforming bacteria. They discovered the substantive nature of some disinfectants, designed to cling to the textile surface and survive the rinse, so that the linen stayed bug-free in the ward linen cupboards.

Sodium hypochlorite bleach is of course an excellent disinfectant, but its use is effectively banned from the healthcare sector because it reacts with hospital disinfectants based on chlorhexidine, to produce indelible brown stains. More recent success has been achieved with peracetic acid, provided this is used in properly designed and controlled washing systems.

As well as achieving disinfection, modern low temperature processes must achieve thorough emulsification of the fatty proteins in body fluids. It is not sufficient to simply match the emulsifying power of the previously used high temperature detergent and alkali systems. Modern high performance hospital textiles usually require some polyester, which has a high attraction for oils and fats. Much higher emulsifying forces are needed to break this bond. Removing gels and small solid particles embedded in the textile also requires much greater enclosure and suspension power, if there is less hot water to swell the yarns. It is easy to see why simply reducing temperature whilst continuing to use old chemistry just does not work!

Beneficial effects of the change

The much-improved low temperature technology built into the latest systems inevitably comes at a cost, but launderers have generally found this cost worth paying. So just what are the benefits? Firstly, there is the obvious cost benefit of lower wash energy. Heating wash water from 10C to 75C consumes (75 – 10) x 4182 Joules/kg per °C = 271.8 kJ per litre. The comparable figure for washing at 40C is only 125.5 kJ/litre. The saving of 146.3 kJ/ litre in a washer extractor is equivalent to 0.04kWh. In a tunnel washer using 2.5 litre/kg textiles into the hot wash zone, the saving would be about 0.1 kWh/ kg dry textiles, plus normal heat losses into the workroom, say 0.12 kWh/kg in total. For a laundry striving to reduce its unit energy consumption from 1.50 down to 1.00 kWh. kg, the saving of 0.12 would get it to 1.38 kWh/kg in just one step.

Making the transition now to low temperature washing also gives a degree of future proofing, for when the wash cost might include electric heating for the wash. Meanwhile, it should be possible to eliminate warm-up time from the hot wash, aiming for an extra load per shift from washer extractors and a slight reduction in stage time in the tunnel washer.

Of more value in many plants is the effect of consistent low temperature on the softening of protein stains and soiling. Many tunnel operators find it difficult to guarantee temperatures below 40C throughout the pre-wash and then have to cope with setting of staining and higher rewash as a consequence. This is a particular problem if recycling of heat into the cold fresh rinse water flow makes it impossible to ensure correct temperatures in the pre-wash. With low temperature washing, the rinse feed can safely be allowed to rise to 38 -40C, enabling maximum use of recycled heat and minimal requirement for anything additional. Users should be looking for a shorter payback on investment ,either in effluent heat recovery, or in recovery from ironer (or tunnel finisher) exhaust where appropriate. This should in turn make possible the progressive reductions in unit energy which the sector has demonstrated in the past, with the accompanying financial benefits. Targets across the sector should soon be pushing down towards 0.80 kWh/kg, especially when electric heating becomes effectively mandatory.

Those laundries which decide to install total water recycling should find that this gives fewer problem with consistent lower temperature, because of the use of low temperature emulsifiers and hence less fat interaction with purification membranes. The lower temperature of final effluent should also reduce the local acceptability problems which some water companies have been raising.

Research work in Germany and elsewhere has suggested that reduced processing temperatures in laundering could usefully extend linen life. This work certainly supports exploring the benefits of reduced ironing temperatures (especially of cotton-rich flatwork), but nothing has yet been published on the effects of lower wash temperatures.

Negative effects of low temperature washing

There is inevitably an increase in the cost of wash chemistry, to meet the need for good low temperature emulsification of oily, fatty contaminants. This is further increased by the cost of low temperature activation of oxygen bleaches, but these will in future be needed only for vegetable dye stains from foodstuffs, drinks and a few medications. The beneficial effects of low temperature processing on protein stain release should result in a marked reduction in residual protein stains, which form a large proportion of any surviving contamination on healthcare work.

There are some launderers believed still to be using high temperatures to improve moisture extraction during the highspeed spin in a washer extractor or in the membrane press. Optimum efficiency here is best achieved by optimising the spin time or maximising the time at pressure in the dewatering press. With energy recycling into the cold rinse water flow (which could soon be economically essential), most launderers will see a slight improvement in water extraction at 38 – 40C, which will have the desirable benefit of reducing energy demand in tumble drying, ironing and tunnel finishing.

Conclusions

So, what actions should forward thinking laundry now be planning? The following checklist might be of help:

• Forward planning for laundering healthcare textiles without fossil fuel
• Low temperature washing has been shown to be both viable and desirable for healthcare textiles, so you should be considering this transition if you have not already done so.
• The first step should be gaining certification to meet the requirements of EN 14065:2016, which enables the safe adoption of low temperature disinfection.
• You should be planning now to instal heat recovery so that the washhouse can run utilising recovered heat. Investigate recovery from ironer and tunnel finisher exhausts. Investigate flash steam utilisation if you are planning to use electric boilers.
• Investigate total water recycling for possible installation in the next five years, because this would reduce the investment cost of recovering heat to run the washhouse
• Monitor quality carefully, to ensure you are getting the maximum benefit of the changes you will be making in the next few years. Use simple one-wash EMPA test-pieces on a regular basis and keep long term records – some effects take time to emerge!
• Monitor and record linen life continually. The cost of circulating stock is considerable, so consciously improving this towards an achievable 200 wash and use cycles for each classification is going to be an essential element of future cost management (see LCN June 2023 issue for how to do the calculation without any stocktaking).