Legionella bacteria are naturally present in cold water.
They are also present in hot water networks at temperatures between 25 and 45°C in conditions that are favourable to their development (nutrients, biofilms). They can cause a serious illness: Legionnaire’s Disease; one which has become a major challenge in terms of public health issues.
The treatments traditionally used against Legionella bacteria are of the chemical biocide variety. There are several disadvantages to these treatments:
- The different parameters for optimal efficiency (dosage, pH, resistance phenomena…) are complex
- The use of continuous injection, which requires high levels of input, may be required, thus raising operating costs
- They generate by products that are rejected into the environment during de-concentration phases
- Chemical biocide injection alone does not always enable full control of the level of Legionella bacteria
Shutting down a system for curative or preventive action against Legionella bacteria is expensive
Biocide injection is no longer the ultimate weapon for destroying Legionella bacteria in water distribution circuits
BIO-UV offers a concept that provides a true bacteriological barrier every time a risk factor is identified:
UV TREATMENT OF COLD WATER FROM THE WATER METER INLET UV TREATMENT OF HOT WATER CLOSED CIRCUITS UV TREATMENT COMBINED WITH PREVENTIVE TREATMENT OF BIOFILMS
TREATMENT OF COLD WATER AT THE INLET
The source of contamination of Legionella bacteria in hot water networks is the cold water inlet (bore holes or other local resources…).
Legionella is a bacteria that is naturally present in water. It is also present in drinking water. Culture analyses (NFT 90-431) highlight some of the germs present, the bacteria that are ‘cultivatable’. PCR analyses show all bacteria, notably the non-cultivatable and cultivatable viable bacteria.
Example of analyses carried out on a water network.
Water source
NFT 90-431 analysis
PCR analysis
Drinking water
Non identifiable
13 000 UG/litre
It is clear that the risk of contamination via cold water is very high.
Erect an initial bacteriological barrier to avoid contamination by new bacteria
A BIO-UV steriliser enables continuous treatment of cold water thus avoiding contamination of water networks:
Example of results obtained:
Water source
PCR result before UV
PCR result after UV
Drinking water
13 000 UG/litre
Non identifiable
< 250 UG/litre
This solution is very easy to apply and has a low investment and maintenance cost.
Analyses carried out by Laboratoire Bouisson Bertrand in Montpellier, an accredited independent laboratory.
TREATMENT OF HOT WATER CIRCUITS
Water in domestic hot water networks is contaminated by Legionella bacteria because:
- The water network design is not always ideal in terms of germ prevention,
- Certain biocide products have operational limits due to phenomena of developed tolerance, concentration dosage management, global water quality parameters (pH, …),
- The biofilm that always forms in the circuit releases Legionella by detachment or abrasion.
Contamination by release from the biofilm must be treated.
Erect a second bacteriological barrier to treat, on a constant basis, the Legionella released by the biofilm.
A BIO-UV steriliser enables continuous treatment of water in a circuit
A significant level of efficiency that enables, during circulation through a closed network, continuous destruction of the legionella released by the biofilms.
BIO-UV sterilisers in the IBP/AM series have been designed specifically for the treatment of hot water at between 35 and 75°C. Unlike standard UV lamps, which are not as efficient beyond temperatures of 40°C, the BIO-UV sterilisers are equipped with dedicated high performance lamps which guarantee performance up to 75°C.
UV TREATMENT OF COLD WATER FROM THE WATER METER INLET
