UV hot water disinfection

Low temperature hot water systems require extra protection from harmful bacteria, such as Legionella, as Taylor Purification explains.

UV water disinfection is a natural process that does not add any chemicals into the water, nor alter the water chemistry. UV light energy inactivates harmful microorganisms, such as bacteria and viruses, by disrupting the DNA—effectively preventing them from multiplying and causing illness. The pathogens are destroyed when the water passes through the disinfection chamber. E. coli, cryptosporidium and giardia are all examples of waterborne microorganisms that cause gastrointestinal illnesses, and that can be controlled with UV disinfection.

Legionella bacteria

Legionella bacteria can cause a serious type of pneumonia (lung infection) called Legionnaires’ disease, or a less serious illness known as Pontiac fever. Legionella bacteria are found naturally in freshwater environments, like lakes and streams. The bacteria can become a health concern when they grow and spread in manmade building water systems. People can get sick when they breathe in small droplets of water in the air that contain the bacteria, or by accidentally ingesting affected water into the lungs while drinking.

People at increased risk from Legionella include people 50 years or older, current or former smokers, those with chronic lung diseases, people with weak immune systems or who take drugs that weaken the immune system (like after a transplant operation

The Greenway 32H Hot Water UV System is an example of a system that’s suitable for hot water reticulation systems under 55°C. Retirement homes, apartment buildings, medical facilities and schools have lower temperature hot water systems, so they require protection from harmful microorganisms, including Legionella bacteria.

or chemotherapy), people with cancer, or people with underlying illnesses such as diabetes, kidney failure or liver failure.

Susceptible hot water systems

In domestic hot water systems, the temperature is typically maintained at 65°C so bacteria cannot grow. However, there are some institutional hot water systems that are kept below 55°C for protection against severe scalding. Below this temperature there is a danger of bacterial growth, and this can lead to serious outbreaks— particularly of Legionnaires’ disease. Retirement homes, apartment buildings, medical facilities and schools are the main places with these susceptible lower temperature hot water systems, so they require protection.

Lower temperature hot water solutions

Various solutions are available, one of which is ultraviolet (UV) disinfection with a hot water UV system. Normal domestic UV systems don’t work very well on hot water applications, as they are intended to run at about 35°C or less, and their output diminishes dramatically at temperatures over 45°C.

The Greenway 32H Hot Water UV System is an example of a system that’s suitable for hot water reticulation systems under 55°C. It can treat flows of up to 8,820 LPH in a single pass situation but has greater capability in a recirculation system where there are multiple passes through the UV. The system incorporates Low Pressure High Output lamps that are specifically designed to operate at higher temperature of 55°C without difficulty and have twice the power of a standard low pressure UV lamp.

About the author: Taylor Purification are the distributors of the Greenway® range of UV disinfection systems. For more information, please visit www.taylor-purification.nz or contact sales@taylor-purification.nz