Thursday, 4 December 2014

Water Dispenser Sanitisation - How to Make it Cost Effective

It is important to understand the definition of “sanitisation” as used in Europe.  Sanitisation combines cleaning and disinfection in a single step.  “Disinfection”, on the other hand, is a single process which follows an initial cleaning step.

The techniques used in dispenser sanitisation can be listed as follows:

·         Replacement of water contact parts by pre-sanitised or disposable components – reservoirs, reservoirs + tubing, taps
·         Manual cleaning and disinfection of components still in place
·         Auto-disinfection

Chemicals, Methods and Utensils
Chemicals include cleaners/acids and disinfectants.  Other methods include ozonation, steam treatment and hot water treatment.  Usual utensils are brushes, paper cloths and scouring pads.

Acids are used for descaling reservoirs/piping and hot tanks.  Phosphoric acid is preferred and various concentrations are available from suppliers from 20-75%.  Increased concentration means more rapid descaling.  Some descalers contain detergents, which sometimes cause excessive foaming with heavy scaling.  Some descaling acids contain a disinfectant component, which enables descaling and disinfection.

Direct chill/spiral chill dispensers require a venturi doser to apply the descaler.  Push-fit fittings should be disconnected at the filter and the venturi doser connected.  Add 25-30ml acid, depending on the concentration, and draw into the dispenser with the chill tap.  Remember to rinse the push-fit fittings afterwards.

Typical disinfectants are listed as follows:

·         Hydrogen peroxide
·         Hydrogen peroxide + silver ions
·         Peracetic acid
·         Ozone
·         Chlorinated materials

Hydrogen peroxide is highly effective against biofilm, leaves no taint and has harmless break-down products.  Peracetic acid is highly effective against biofilm, a small dosage is needed but residual product needs to be rinsed out thoroughly.  Chlorinated materials can create a taint issue if not rinsed out thoroughly and biofilm can resist.  An exception is chlorine dioxide, which leaves no taint and is very effective against biofilm.  The disadvantage of chlorine dioxide is that it has to be generated in situ because of stability issues.  However tablets are available, which generate the disinfectant on addition to water, although these are expensive.  Ozone can be generated with a portable kit and is effective against biofilm.  However it does create an ozone smell in the environment around the dispenser.  Steam provides effective sterilisation in 4 minutes with some units on the market.  However, care is needed in operation.

New Technologies – Auto Disinfection
Auto disinfection is possible with the following materials:

·         Ozone
·         UV
·         Hot Water
·         Silver and Copper

Ozone may be used by ozonating the water in the reservoir on a timed basis overnight.  Another technique ozonates the last section of the supply circuit prior to the tap outlet.  UV may be used to irradiate the reservoir contents or the water line just prior to the tap outlet.  A further technique irradiates the total tap outlet area.  Hot water disinfection uses hot water generated by the hot tank.  A microprocessor releases water into the rest of the dispenser and continues to heat until near boiling. 

Silver may be incorporated into plastic components.  This provides more of a bacteriostatic effect than germ-kill.  The treated plastic works well at low temperatures (5oC), but is unable to cope at ambient temperature.  Copper is used in pipework.  It has a bacteriostatic action, but oxidation and subsequent passivation of the copper surfaces can reduce this effect.  Copper-silver alloys, unlike copper alone, can generate an electrolytic effect which provides better germ-kill.

Cooler Maintenance
Despite all the new technologies, a sanitary maintenance visit is still required to clean and disinfect the dispenser head, taps exterior and drip tray, otherwise poor in-house maintenance and difficult environments will always pose a problem for hygienic dispensing of water.  High-use dispensers are particularly vulnerable to tap contamination, including colonisation with Pseudomonas aeruginosa.  Sani-cloths may solve the problem for flat surfaces, but a disinfectant spray is necessary for tap areas.  A hydrogen peroxide spray provides a good germ-kill effect in the tap area, but the effect is not long-lasting.  New sprays are now available on the market which provide a long-lasting effect and these are to be recommended.

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