Brian Stother, Managing Director of Purite Ltd, explains how hospital SSDs can capitalise on the latest purification technology.

The growth in the numbers of nosocomial or hospital acquired infections (HAI) in recent years is focussing the attentions of medical and administrative staff alike on the need to improve both the quality and management of hygiene regimes. For example, a study carried out by The London School of Hygiene and Tropical Medicine estimated that HAIs affect around 9% of the patient population, adding some £1 billion to the annual costs of running the NHS in England alone.

Strategic management of infection control is a core discipline in the health sector, ranging from essential cleaning of hospital wards and hand-washing protocols to sophisticated surveillance, analytical and screening techniques. An important element in infection control regimes is the effective use of purified water in decontamination processes, especially in equipment disinfection and sterilisation, where high purity water is used as a final rinsing agent to remove residual traces of contamination or detergent from washer-disinfectors and to provide steam for thermal disinfection and steam sterilisation.

Although the mains water supply commonly used by hospitals has been treated to ensure it is potable, its overall quality can be extremely variable and, even in the best areas, is still unsuitable for use with disinfection equipment as it contains dissolved solids and micro-organisms.

Consequently, the (S)HTM 2030/2031 standard is now used to govern the quality of water used for washer disinfectors and steam generators. This standard provides recommended limits for key parameters such as electrical conductivity, total dissolved solids (TDS) content and water hardness, plus the acceptable concentrations of chlorides, heavy metals, iron, phosphate and silicate and the maximum levels of bacterial endotoxins and the total viable count of micro-organisms.

(S)HTM 2030/2031 also means that feed-water has to be treated or purified to ensure that it does not introduce contaminants into subsequent stages of the cleaning and sterilisation process. It is, therefore, essential for water purification equipment to be correctly designed, manufactured, installed and maintained.

One of the most effective processes in providing a supply of consistently high purity water is reverse osmosis (RO), where a conventional mains supply is fed under pressure into a module containing a semi-permeable membrane. The membrane removes a high proportion of impurities, including up to 98% of inorganic ions, together with virtually all colloids, micro-organisms, endotoxins and macromolecules, with almost 70% of the feed-water passing through the membrane as a purified permeate, with impurities being removed in a residual concentrate stream that is run to drain.

RO systems generally include a pre-treatment package designed to meet the characteristics of the feed-water. Typically, this equipment includes a base-exchange softener to remove hardness that would otherwise scale downstream membranes and, where necessary, to provide a flow of softened water directly to the washer-disinfectors. Further protection is provided by passing the water through activated carbon filters, to remove free chlorine and organic contaminants, with any remaining particulates being removed by a fine filter before the pre-treated water enters the RO plant.

The latest developments in water purification technology mean that many systems require relatively little space for installation, being designed so that a duty or standby RO unit can provide purified feed-water for both washer disinfectors and clean steam generators; a heated distribution ring main can be added to maintain microbial integrity after final sub-micron filtration has been used to remove bacteria and endotoxins.

Finally, portable and self-contained containerised RO units can be located outside hospital buildings to maximise the space available internally. These systems can be installed quickly and simply, with a minimum of disruption to hospital schedules; once in place they have low operating costs, requiring minimal maintenance or user intervention, and can be used to provide a 24/7 supply of high purity water to improve hygiene and combat HAIs.