Swimming Pool Water Disinfection and How Ultraviolet Light can reduce Pool running costs

Why some chemicals must be used in the disinfection of Pool Water

Many people hear the word 'chlorine' and are immediately reminded of their local municipal pool where the smell hits you like a wall as you walk through the doors.

Chlorine has a bad reputation because of this – what many people do not know is that Chlorine is the number one chemical used in the disinfection of a lot of food products and the water in your tap!

We have all heard the stories of A-list celebrities who did nude photoshoots when they were poor and struggling actors and actresses, only for the images to resurface years later damaging very lucrative and succesful careers... Chlorine's nude photos are municipal pools – and unfortunately this is what people remember when talking about chlorine. Chlorine isn't remembered for it's disinfection of drinking water keeping people in the United Kingdrom safe from dangerous bacteria and viruses.

I'm not here to bring down municpal pools because they are such important facilities, but many are understaffed and overcrowded.

Why do we need to disinfect the water in our swimming pools?

Why do we need to add chlorine to our pool water if the water comes out of the tap and is safe to drink?

The answer is people.

You wouldn't fill the kitchen sink up, wash your baby in it and then drink a glass of the water, would you? Well, it's the same in your swimming pool. One person can lose up to 70L of sweat during one swimming session. And the local swimming pool probably sees a lot of people every day.

are or believe they are allergic to chlorine and want a swimming pool that does not rely on it to disinfect the water. Unfortunately this is not possible at the present time because there is no other form of water treatment that is guaranteed to be safe. Probably every healthy pool in the world uses either Chlorine, Bromine or Peroxide and this article explains why that is the case.

All three of these chemicals work in the same way and all have the same drawback that you are swimming in a chemical soup!

Diseases that can occur 


Swimming pool water contains bacteria that can cause many types of diseases in humans. The bacteria that cause these diseases are known as pathogenic bacteria and the pool water disinfection process must kill these for the pool to be safe to swim in. 
The disinfection of Water in the past has always relied on Chlorine because it is a very efficient sanitizer and has always been relatively cheap. However it is getting more expensive and there are a few doubts about its absolute safety when people are exposed to it over a long term. Because of this plenty of research has been carried out to find other methods of cheap, reliable water treatment that will kill the pathogens. 


What are the Alternative Disinfectants to Chlorine or Bromine? 

 

The water disinfection properties of ultraviolet light were discovered over 100 years ago. The light must be at a specific wavelength and power to treat the water as it passes through a treatment cell. The UV light causes biological changes that kill the pathogens and significantly reduce the concentration of bacteria in the water, without leaving any dangerous by-products. 
However the water must be totally transparent without any turbidity for the UV light to be totally effective (Turbidity is a measure of how transparent water is and increases due to the presence of particles in the water). 
It is also very difficult to measure how effective the UV light treatment is. With Chlorine this is easy because the water is treated with sufficient chemical to make sure that there is enough residual chlorine to ensure that the pool water is safe. 
So the UV treatment needs a filter to ensure that the water is never cloudy, but this filter will also harbour a seething mass of bacteria (See other article on Swimming Pool Water Quality). 
The result of all this is that UV can be used to reduce the amount of chemicals used but every pool will still need a residual level of chlorine in the water for it to be 100% safe.

Untitled document

Swimming Pool Water Disinfection and How Ultraviolet Light can reduce Pool running costs

Why some chemicals must be used in the disinfection of Pool Water

Many people hear the word 'chlorine' and are immediately reminded of their local municipal pool where the smell hits you like a wall as you walk through the doors.

Chlorine has a bad reputation because of this – what many people do not know is that Chlorine is the number one chemical used in the disinfection of a lot of food products and the water in your tap!

We have all heard the stories of A-list celebrities who did nude photoshoots when they were poor and struggling actors and actresses, only for the images to resurface years later damaging very lucrative and succesful careers... Chlorine's nude photos are municipal pools – and unfortunately this is what people remember when talking about chlorine. Chlorine isn't remembered for it's disinfection of drinking water keeping people in the United Kingdrom safe from dangerous bacteria and viruses.

I'm not here to bring down municpal pools because they are such important facilities, but many are understaffed and overcrowded.

Why do we need to disinfect the water in our swimming pools?

Why do we need to add chlorine to our pool water if the water comes out of the tap and is safe to drink?

The answer is people.

You wouldn't fill the kitchen sink up, wash your baby in it and then drink a glass of the water, would you? Well, it's the same in your swimming pool. One person can lose up to 70L of sweat during one swimming session. And the local swimming pool probably sees a lot of people every day.

are or believe they are allergic to chlorine and want a swimming pool that does not rely on it to disinfect the water. Unfortunately this is not possible at the present time because there is no other form of water treatment that is guaranteed to be safe. Probably every healthy pool in the world uses either Chlorine, Bromine or Peroxide and this article explains why that is the case.

All three of these chemicals work in the same way and all have the same drawback that you are swimming in a chemical soup!

Diseases that can occur 


Swimming pool water contains bacteria that can cause many types of diseases in humans. The bacteria that cause these diseases are known as pathogenic bacteria and the pool water disinfection process must kill these for the pool to be safe to swim in. 
The disinfection of Water in the past has always relied on Chlorine because it is a very efficient sanitizer and has always been relatively cheap. However it is getting more expensive and there are a few doubts about its absolute safety when people are exposed to it over a long term. Because of this plenty of research has been carried out to find other methods of cheap, reliable water treatment that will kill the pathogens. 


What are the Alternative Disinfectants to Chlorine or Bromine? 

 

The water disinfection properties of ultraviolet light were discovered over 100 years ago. The light must be at a specific wavelength and power to treat the water as it passes through a treatment cell. The UV light causes biological changes that kill the pathogens and significantly reduce the concentration of bacteria in the water, without leaving any dangerous by-products. 
However the water must be totally transparent without any turbidity for the UV light to be totally effective (Turbidity is a measure of how transparent water is and increases due to the presence of particles in the water). 
It is also very difficult to measure how effective the UV light treatment is. With Chlorine this is easy because the water is treated with sufficient chemical to make sure that there is enough residual chlorine to ensure that the pool water is safe. 
So the UV treatment needs a filter to ensure that the water is never cloudy, but this filter will also harbour a seething mass of bacteria (See other article on Swimming Pool Water Quality). 
The result of all this is that UV can be used to reduce the amount of chemicals used but every pool will still need a residual level of chlorine in the water for it to be 100% safe.

Ultra Violet light has been used in swimming pools in recent years because it has been found that it is very effective at neutralising bacteria in pool water. The water passes through the UV cell that is plumbed into the pipework in the plant room and as the water passes the UV light disrupts the DNA of bacteria rendering it inert and therefore no longer harmful to bathers.

The pool industry calls this secondary disinfection. UV cannot be used alone in a pool because depending on the hydraulics and the use of the pool it may take some time before all the water in the pool passes through the UV lamp. It is therefore necessary to have some residual chlorine in the pool water in order to disinfect the pool water whilst bathers are swimming.

The use of UV does mean that less chemicals can be used in the pool water itself. Typically with the use of Ultra Violet light, in conjuction with an effective Chlorination regime, good filtration and regular dilution of the pool water it is possible to lower Free Chlorine levels in the pool to 0.5 – 0.8mg/L which is close to the levels acceptable in drinking water that comes from the tap in the UK.

It is essential that the pool water is crystal clear in order for the UV to work. If the water is cloudy there is a higher risk that bacteria can be sheltered from the harmful UV light behind debri in the water.

Bluepools now specialises in the design and installation of pool water disinfection systems that rely predominantly on disinfection using anUltra Violet light cell.

This works on the basis that a small power pump runs 24/7 so that the whole pool water volume ontinuously passes throught the UV at a rate of 4 timed per day.

The extra cost of running the small pump continuously is far less then the cost of the chemicals that would be used if the pool relied exclusively on chlorine dosing and at the same time has the benefit of reducing the pool water chlorine content to a level very close to that which cpmes out of your kitchen tap!

 
How UV works


Ozone is generated when a molecule of oxygen is illuminated by high energy ultraviolet light. It is formed when three atoms of oxygen are bound together instead of the normal two. The extra oxygen atom makes ozone a highly energetic oxidiser and very efficient pathogen killer.
It is produced for swimming pool water using two different methods. In the UV method, air is passed over a UV bulb, and the radiation creates nascent oxygen and then ozone. In the corona discharge method, a small lightning storm is created in an air filled chamber. 
Ozone is a powerful sanitizer, but it is a gas. 
Its primary drawback is that it quickly reverts back to oxygen and so it is currently impossible to ensure that all the water in a pool has been treated. The short life span of ozone and the difficulty of ensuring even distribution throughout the water that is being treated results in a requirement for a low residual level of chlorine as in UV light sanitation. 
However the actual chlorine usage is reduced by about 80% and there is no doubt that ozone sanitation use will continue to increase in the pool industry. It gives water a better smell, taste and clarity than chlorine alone, and it produces no by-products. 
Ozone also removes certain dissolved metals and rids the pool of soaps, scum, oils and chloramines.

It is probably the pool water sanitation system of the future