Raising the hot water tank temperature to 60-700
C- Thermal eradication provides only temporary results: it is very labour intensive, presents scalding risks, has associated high energy costs and corrosion problems, is difficult to achieve complete effectiveness and at best provides only short term (weeks to months)effectiveness.
Shock treatment at 20 to 500 ppm provides only temporary results and is corrosive to pipes and produces potentially carcinogenic DBP’s. Continuous chlorination at 1-2 ppm is not effective. Chlorine is significantly less effective in hot water systems which are the main foci of Legionella proliferation.
Provides effective point of source disinfection only, but no residual and thus not effective for systems already contaminated. High energy costs and requires very clean water with low turbidity and suspended solids.
Must be generated onsite and commercially available treatment plant costs for small scale systems such as hospitals and hotels are high. This method, while effective involves possible health risks and has been disallowed in some countries.
In a paper published in the Journal of Hospital Infection (Prince, 2002); a comprehensive sampling protocol was employed to evaluate the efficacy of electrochemically activated water, against legionellae and heterotrophic bacteria in two industrial cooling tower systems.
Both of the towers in the study remained free from evidence of Legionella spp. contamination throughout a five-month evaluation period, despite the previously demonstrated presence of legionellae in one of the test towers, and in two other towers on the same site, at levels well in excess of UK Health and Safety Commission (HSC) Approved Code of Practice and Guidance (ACOP) upper action limits.
Levels of heterotrophic bacteria were controlled below 10 cfu/mL in both towers throughout most of the trial. Results also provided indirect evidence of significant activity against biofilm bacteria, with biofilm removal beginning almost immediately after commissioning of the electrochemically activated water treatment systems. The results were particularly encouraging as the two towers studied had a long history of poor microbiological control using conventional bromine-based biocide products.
Legionnaires’ disease, or Legionellosis, is a severe infection caused by Legionella species, primarily L. pneumophila. The disease typically presents as pneumonia and symptoms may include a high fever, chills, cough, muscle aches, headaches, and diarrhoea.
The major source for legionella is water distribution systems of large buildings, including hotels and hospitals and the cooling towers of various industries. Recent evidence suggests that "Aspiration" (choking such that secretions in the mouth get past the choking reflexes and enter the lung) is the most common way that bacteria enter into the lungs to cause pneumonia.
Legionella is widespread in nature and found in low quantities in most surface water. It proliferates most in stagnant warm water (± 40°C). This makes it relatively easy for homes and businesses to inadvertently cause fatal infections and outbreaks in workers and the wider public.