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Hygiene In Hot Water Systems

biofilm on rubber shower hose
biofilm on rubber shower hose
Bacteria sampled from a tap outlet
microbiological sample from a tap outlet
Reasons for contaminated systems 
There are many reasons why a water system can become contaminated with pathogens such as Legionella or Pseudomonas. It is likely that the pathogens are already in any water system, but at low concentrations where they will not have any effect on health. Problems arise when the pathogens are able to reach high concentrations and where there is also an exposure route. 

The reasons that contamination occurs in the pipework can include water temperatures, over-sized pipework (or other installation mistakes), long travel distances, long stagnation phases, short circuits in the cold water/warm water system, dead legs, not enough thermal disinfection, retrograde contamination or simply a growing bio-film colony in the hot and cold water systems. The age of the system is one of the less important factors, though the older the system the higher the chance for dead legs and areas of stagnation. In addition the piping materials have an influence on the speed and extent of bacterial colonisation i.e. iron is a source of nutrients for bacteria and is a good growing medium for biofilm, copper is mildly phytotoxic and plastic makes a good base for biofilm.  

Contamination in warm water systems 
The largest threat of microbiological contamination from legionella exists in hot water systems. Normally with the use of a thermal disinfection and continously high water temperatures in the hot water system (≥ 60°C) the growth rate of legionella should be controlled. For this methodology to be completely effective it must be ensured that the water temperature stays continously high. 

 As a rough rule, at water temperatures of below 20°C Legionella will not reproduce, the optimum temperature for Legionella to thrive is 25°C- 45°C, above 50°C the growth rate should slow or stop and above 60°C should kill the bacteria. It should be noted that biofilm can shelter the bacteria and that if temperatures are not maintained they may well remerge shortly after heat treatment. There is evidence from American hospital testing that recollonation can occur within two weeks. 

It should be noted that water systems typically include thermal mixing valves in advance of showers and taps, these devices control the water temperature at the outlet to prevent scalding, it also means that the water will typically not exceed 45°C beyond this point. As a result please note that the implementation of this measure is not a guarentee for a legionella free water network. If an increase in legionella count is detected a thermal disinfection could be implemented to reduce the count. To implement this measurement you have to flush water at every tap point of the system with a temperature of 70°C for a period of time. This thermal disinfection is an immediate step to achieve a germ reduction, for continuous sanitation additional steps should also be taken. As a precondition of a thermal sanitation the water system has to be planned and installed in a way that ensures that the necessary water temperature of > 70°C can be reached at every exit / tap point and all through the pipework system. You must also take steps to prevent scalding. Thermal disinfection has a high energy and labour cost related to the amount of hot water you will require for disinfection and scald risk management, in addition it puts stress on your pipe systems. It should be noted that thermal disinfection alone may not have the desired hygienic success.

A statistical check of about 20,000 tests in Germany (BMBF-Verbundprojekt, biofilm in drinking water installations, see also above) concluded that Legionella was found in 12 % of all the hot water tests conducted and that almost 3% also included Pseudomonas, both bacteria were also found in cold water systems more than was expected, (Knowlege resulted from the BMBF-Verbundprojekt „Biofilme in drinking water-nstallation“, Prof. Dr. Hans-Curt Flemming, IWW Mühlheim, Moritzstraße 26, 45476 Mühlheim). 

An issue that has not received a lot of attention yet (except in hospitals) is the occurrence of Pseudomonas, which is one of the most important opportunistic pathogens, and which has a hugh growing potential in technical water systems.  This bacteria typically enters the water system through retrograde contamination at the tap, this area is beyond the thermal mixing valves and never achieves high temperatures.

How the Aquadron Addresses Water Hygiene
The Aquadron treats all of the water that passes through the system, it does this by proportionally dosing all of the water with Anolyte, 24 hours a day, seven days a week. The Anolyte passes through the whole system, removing biofilm and killing bacteria, it even works in the shower heads and taps, at a point that is beyond the thermal mixing valves and that is not protected by thermal treatment. This ensures that Legionella colonies can not form in the pipework system.

Once the system has been disinfected it is possible to operate without the thermal barrier, this means that water temperatures can be reduced. This saves energy and money - the net effect is that you get improved water treatment with far higher levels of safety and energy savings pay for the system. Click here for details of the potential cost savings.

Click here for more details on the Aquadron Legionella System.

Click here for project examples in hospitals and care homes.
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