Water purification for sterile services, decontamination and endoscope reprocessing
High quality purified water is critical for use with washer disinfectors, automated endoscope reprocessors (AERs) autoclaves and steam sterilisation systems, for cleaning and decontaminating endoscopes and other hospital instruments.
In each case, raw source water, normally drawn from mains supplies, must be purified to meet the requirements of the latest HTM guidelines. These include:
HTM 01-01 part a
HTM 01-01 part b
HTM 01-06 part c and part e
Part c covers the operation of washer-disinfectors, with reference to the supply of purified water for process and final rinse water. Part e covers the testing regime and specifies the permitted maximum level of measurements such as acidity (pH), electrical conductivity, hardness and total viable count (TVC) of micro-organisms.
Water purification technologies
Reverse osmosis is a proven and highly effective method of removing inorganic ions and larger, non-ionic contaminants from raw water streams. An RO system operates by passing pressurised feedwater through a specialised semi-permeable membrane, which is capable of rejecting up to 98% of the mineral salts, silica and organic compounds and over 99% of bacteria that may be present, and produces a stream of purified water known as the permeate. A waste or concentrate stream containing the rejected impurities is also produced that can often be recycled.
By comparison, deionisation technology removes ions and charged particles either using electric fields or through ion exchange in resin beds. Although deionisation can produce a higher purity of water than RO, the latter is more than adequate to meet the needs of sterile services and decontamination services, as defined by the HTM guidelines.
From a practical perspective it should also be noted that:
- RO is cheaper to install and operate than DI
- RO removes particulate matter, organic molecules and pyrogens that cannot be eliminated using DI
- RO water is less corrosive to steel and copper pipework and storage vessels than DI water
- RO systems are simpler and less expensive to maintain that DI plant.
Case study: Edinburgh Royal Infirmary
A Purite hot sensitisation system is crucial in the ongoing modernisation and expansion at Edinburgh Royal Infirmary.
This upgrade enhances the existing cold reverse osmosis water purification plant, enabling the Hospital Sterilisation Decontamination Unit (HSDU) to improve service quality and meet growing demand from the NHS Lothian region.
