About Legionella Pneumophila

These micro-organisms:

  • are pathogenic, rod shaped gram-negative bacteria with size of about 1×2 microns
  • are naturally present in most waters (endemic to most public water supplies)
  • multiply easy in contained water areas with stagnant water between 32-40°C
  • cannot sustain temperatures above 60°C
  • are oxygen loving bacteria
  • can cause inflammation of the lungs by inhalation
  • are most commonly causing sickness by aspirating contaminated air and aerolized water droplets.
  • can cause legionellosis (legionella pneumophila, often called legionnaires disease) or the non-fatal Pontic Fever.
  • are a public health concern due to possible large outbreaks (ex. Philadelphia, July 1976)

Places of special concern:

  • cooling towers (power plants and large air conditioning systems of buildings and ship’s)
  • public shower installations (especially older installations and when not continuously in use)
  • hospitals (especially vulnerable are transplant patients, people that need anesthesia and intubation)
  • whirlpools, steam baths and hot-tubs
  • specific buildings for expositions and tradeshows
  • the bottom of tanks and water heaters (concentration of Mg and Ca scaling contributes to their presence)

Regular methods of ‘removal’ are:

  • (shock) hyperchlorination (up to 50ppm) and flushing, which is time consuming and not environmentally friendly.
  • continuous chlorination (3-4ppm), which merely suppresses L.pneumophila and is not beneficial for health.
  • heat (>60°C) treatment, which also takes time/energy and is not always possible or desired.
  • partly with UV light treatment (at 254nm) which damages DNA and is not sufficient on its own.


We have studies and references that ultrasound can reduce colonization and consequently eliminate these pathogenic bacteria over time.

Hereby, the treated installation can remain in service and no dismantling is needed.

Other studies :  ncbi-1-Research                            ncbi-2-Research

About the outbreak in Warstein, Germany

Recently in the news :



Picture: deadly diseases and epidemics,

Jon Zonderman & Laurel Shader, M.D
infobase publishing 2006.

European guidelines


Watertreatment and biofilm prevention