Endoscope washer disinfector water compliance — is reverse osmosis the answer?

Tristel Pty Ltd
Thursday, 01 October, 2020

AS/NZS 4187 is changing, with water quality requirements for both CSSD and endoscopy revised in line with ISO 15883 and HTM 01-06. However, the requirements for CSSD and endoscopy vary greatly, so there may not be a one-size-fits-all solution with conventional products. While reverse osmosis (RO) is a commonly discussed solution, how suitable is it for endoscopy?

Historically, RO systems have been used for CSSD departments with variable success rates. When it comes to endoscopy departments, RO systems can be problematic in maintaining bacteria-free water quality. RO systems require a ringmain; an expensive piping system downstream of the RO that can supply endoscope washer disinfectors (EWDs) and circulate RO water back to the system. If the ringmain is not installed by the manufacturer, they may refuse to guarantee the water quality of the system. The manufacturer of the RO only guarantees bacteria-free water within their own system and ringmain. This means that installation of an RO system may not cure existing water quality issues that could be faced in the endoscopy department.

If there is an existing ringmain, super chlorination will need to be performed, filters changed, and the source of the contamination assessed. The question remains; when water sampling yields a positive result, who owns the no man’s land between RO and EWD? While RO systems may be suited to CSSD, they may be an expensive and imperfect solution for the more stringent EWD Rinse Water requirements under AS/NZS-4187.

Endoscopy requires its own unique solution. Tristel has nearly three decades of experience in endoscopy, and developed the Tristel RA (Rinse Assure) System specifically for use with EWDs. Tristel RA is a small, streamlined unit that can be installed next to EWDs, or in an adjacent room. During the design and concept stages of Tristel RA, Tristel analysed ISO 15883 and HTM 01-06 and designed a product to fully comply with these standards.

Tristel RA combines pre-filtration from 5-micron to 0.2-micron, water deionisation, RO and the addition of a non-toxic disinfectant — a combination of all methods for water treatment, designed to tick every box for supplying and maintaining bacteria-free water to your EWD. No other product on the market was designed specifically for endoscopy, and guarantees bacteria-free rinse water.

The unique feature of Tristel RA lies within Tristel’s patented chlorine dioxide chemistry. Chlorine dioxide is recognised by the World Health Organization for safe treatment of drinking water. There are numerous studies comparing chlorine dioxide, chlorine and thermal disinfection; with the most recognisable study carried out by Johns Hopkins University in the USA. The study concluded that chlorine dioxide is efficacious in eliminating Legionella, gram-negative bacteria and biofilm. In comparison, hyper-chlorination was unable to achieve this, nor function successfully as a remediation shock treatment. Super-heated water was also unable to achieve this, nor function successfully as a remediation shock treatment.

Tristel RA automatically doses pre-set levels of chlorine dioxide at low levels into the incoming water supply used during an EWD’s cycle. The chemistry is generated by mixing Tristel Base Solution (citric acid) and Tristel Activator Solution (sodium chlorite) at point of use. Chlorine dioxide is compatible with materials within an EWD at the concentration dosed by Tristel RA. Chlorine dioxide as dosed by Tristel RA does not damage endoscopes and does not affect the chemical composition and efficacy of detergents (including enzymatic) and disinfectants (including peracetic acid) commonly used in EWDs.

The following statements are mentioned in HTM 01-06, which were used both to develop Tristel RA, and to develop AS/NZS-4187 Table 7.3:

  • “Residual chlorine remaining in a reprocessed endoscope may reduce the possibility of biofilm formation and growth of contaminants” (HTM 01-06 Part B - 2.62).
  • “The addition of a non-toxic biocide to the final rinse-water may help prevent the formation of biofilm” (HTM 01-06 Part B - 2.82).

While both being oxidative agents and sharing a word, ‘chlorine’ and ‘chlorine dioxide’ have very different properties. Chlorine dioxide is roughly two and a half times more powerful than chlorine on a molecule for molecule basis, and is a selective (rather than reactive) chemistry. This is why low concentrations are effective, without the negative side effects associated with chlorine.

Tristel RA doses between 1.5–2.5 ppm of chlorine dioxide; drinking water is 0.5–0.8 ppm, and the Standards allow up to 10 ppm for EWDs. A constant presence of even low levels of chlorine dioxide provides the solution to existing water quality issues and peace of mind moving forward, with water compliant with AS/NZS 4187 Table 7.3 and associated Standards.

Tristel carried out an initial case study in the Endoscopy Department of a hospital in Wales (UK) that was known to have water quality issues. Prior to installation, three laboratories took full water samples to assess current quality of water supplied to four EWDs. Results showed high total viable counts (TVC) after two days, some as high as 236. TVCs increased to more than 900 after five days.

Tristel RA was installed to dose two of four EWDs in the department. The two remaining EWDs continued to operate as usual to act as control bays. Upon installation of Tristel RA, several high-dose cycles were run to purge the EWDs. Daily samples were taken by the hospital and sent to three laboratories for testing. Five days after installation, water samples taken from machines supplied by Tristel RA showed zero TVCs.

The Tristel RA base is quickly approaching 50 installations worldwide. Since the first Tristel RA was installed in 2015, no site has reported a failed water sample. Tristel RA is approaching 3000 final rinse water samples globally without failure.

Concerned about compliance with AS/NZS-4187 Table 7.3? Contact Tristel to find out more about Tristel RA.

For more information: https://www.tristel.com/au/tristel-products/tristel-ra.

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