Why is Electrochlorination the best choice for swimming pool disinfection?

All swimming pools should be regularly and thoroughly disinfected. This eliminates harmful pathogens that cause sickness in swimmers and prevents the growth of other biological organisms, such as algae. Commercial pools come in all shapes and sizes and there may be multiple pools on a single site, each one requiring tailored disinfection depending on water volume and usage.

There are several different pool disinfection techniques currently available to pool managers.

Chemical Pool Disinfection

Commercial chemicals such as sodium hypochlorite or calcium hypochlorite are often used for the pool disinfection process. These chemicals are highly effective, but they can present problems if stored or handled incorrectly. Maintaining a safe and constant chemical supply can also be expensive.

Sodium Hypochloriirte is made on a industrial scale by reacting caustic with chlorine gas. It is delivered to site either in 20 litre containers or as a pumped over delivery into site storage tanks. When added to a pool, it attacks the microbial cell walls of any viruses, bacteria and fungi, breaking them down and preventing them from reproducing. The sodium hypochlorite solution needs to be carefully stored and managed as it degrades over time, or if exposed to sunlight, high temperatures or vibrations. It is also a major irritant to human skin and eyes, so should only be handled by trained staff wearing protective gear.

Calcium hypochlorite (Ca(OCl)2), created by combining calcium oxide (lime) with chlorine gas, usually comes in tablet or granulated powder form. It is supplied in 45 kg containers. Measured doses are added to water to form hydrochloric acid, which works in the same way as Sodium Hypochlorite to destroy harmful organisms in the water. ‘Cal Hypo’ is easy to buy, transport and store in powdered form, and has a shelf life of 2-3 years.

It reacts to sunlight and it should be diluted so it won’t form liquid bleach. If misused or mishandled, cal hypo is also an irritant. Additionally, it adds calcium to the pool water and this may lead to calcium scaling on tiles and equipment over time.

Ultraviolet (UV) Pool Disinfection

Ultraviolet light rays have germicidal properties and are increasingly used to sanitise water, surfaces and even air supply, The UV light targets the DNA or RNA of algae, fungi, viruses, bacteria and any other micro-organisms in the water, preventing reproduction and growth. It’s environmentally friendly as it creates no chemical by-products. However, it can be expensive to install and needs to run 24/7. It won’t remove non-biological contaminants (such as excess chlorine or salts). It only works in clear water — cloudy water may need additional filtering before the UV disinfection can get to work. UV Radiation can remove

Electrochlorination Disinfection

Electrochlorination is the process of generating Sodium Hypochlorite from a brine solution via the simple process of electrolysis. Electrolysis of brine is a tried and trusted technique and electrochlorinators have been sold for the disinfection of water for decades. The outlay cost for an electrochlorinator has come down over time, which now makes it a viable alternative to the continuous procurement of raw materials necessary for chemical pool disinfection. 

How Does Electrochlorination Work?

An electrochlorinator generates Sodium Hypochlorite from a high quality salt. Several 25 kg bags of salt are added to a brine tank and mixed with softened water. Some of the salt dissolves in the water until it becomes a saturated brine solution i.e. no more salt can dissolve. This brine solution is then diluted to a 3% concentration where it passes through an electrolytic cell and produces Sodium Hypochlorite. The resultant Sodium Hypochlorite solution is stored in a small tank where it can be metered into a pool under the control of a pool controller. During the process a number of reactions take place inside the cell but they can be summarised as:

2NaCl + 2H2O → NaCl + NaClO + 2H2

The sodium hypochlorite generated is typically 0.7% solution strength. This electrolytic generated Sodium Hypochlorite is significantly lower strength than commercial hypochlorite (14-15%), which is a benefit for many applications including pool disinfection. 

What Does Electrochlorination Cost?

One major advantage of generating Sodium Hypochlorite at site with an electrochlorinator is reduced costs. As a quick comparison:

• Each kg of chlorine generated by an electrochlorinator requires approx. 3.5kg of salt.  
• A 20 litre container of 14%-15% Sodium Hypochlorite contains approx. 2.8 kg of Chlorine. 
• A 45kg container of Calcium Hypochlorite  (approx. 68% active ingredient) contains 30.6 kg of chlorine. 

The following table shows the chemical costs in terms of salt to generate a single 45kg container of calcium hypochlorite and 20 litres of sodium hypochlorite:

1. Based on the cost of a 25 kg bag of salt at £5.75.

From this table it’s easy to compare potential chemical costs against the equivalent costs of switching to an electrochlorinator. From this we are able to calculate the payback period for each site. This often demonstrates an immediate benefit on the Profit and Loss accounts as the capital cost of systems are normally ammortised over an asset’s lifetime.

So why is it better to generate Sodium Hypochlorite onsite?  Sodium Hypochlorite from an electrochlorinator has several advantages over purchased chemicals. These can be summarised under the following headings:

RUNNING COST

The costs of salt versus commercial chemicals have already been discussed. There is clearly a lower running cost for pools using electrochlorination, which often generates a reasonable payback for the capital investment. 

HEALTH & SAFETY

Commercial Sodium Hypochlorite is classed as hazardous at 5% concentration or higher. At 0.7% the electrolytically generated Sodium Hypochlorite is significantly safer in comparison to both commercial Sodium Hypochlorite and Calcium Hypochlorite. Lower COSHH risks for employees is a big benefit..

The only chemical handled by employees is salt. There no risk to employees to being exposed to salt, further reducing chemical risks within the plant room

The second risk is the elimination of the risk of filling the wrong tank, as may happen when using Sodium Hypochlorite or Calcium Hypochlorite. High risk incidents occur when acid is inadvertently mixed with sodium hypochlorite. This produces toxic chlorine gas. There is no such risk with an electrochlorinator as only one tank (acid tank) is ever filled manually. 

CHEMICAL MANAGEMENT & PROCUREMENT

The only chemical required for the onsite generation of hypochlorite is salt. Salt is available in 25kg bags and delivered in pallet loads of up to 49 bags. Salt can be safely stored indefinitely in a range of temperatures, making it easy to procure and easy to store.

BUSINESS SUSTAINABILITY

Prices of commercial chemicals fluctuate,and they may become scarce or even unavailable. This affects the ongoing business operation of a swimming pool. If the water isn’t disinfected to established standards then the pool has to close. Even a short closure can affect revenue. Chemicals are part of the supply chain and their availability can be curtailed by the pandemic or other external factors, such as the closing of a factory or industrial action. 

Salt is mined and refined in the UK and is produced in large quantities by several companies. It’s a standard commodity, stable in price. It is easy and low cost to buy ahead and simple to store in times of difficulty.   

ENVIRONMENTAL GAINS

Salt is a readily available resource mined and refined in the UK and is delivered in its raw form. Chemicals such as Sodium Hypochlorite  and Calcium Hypochlorite are nearly always imported from overseas, so there is a major environmental cost involved in their transport.

Why Use Prodose for Your Electrochlorination Needs?

Prodose manufactures the Ampro range of highly cost effective and uniquely controllable electrochlorinators. We have built these systems to multiple specifications from more than a hundred UK and overseas projects, that include a range of different sized swimming pools. The range of Ampro electrochlorinators come with a complete after-sales support and if necessary can be installed by third parties.

As part of our customer commitment, we assess each swimming pool disinfection project individually as we pride ourselves on always aiming to specify the most suitable equipment to meet your requirements. Given we are not tied into any particular manufacturer or on commission to sell certain products means we are entirely impartial and can supply a range of equipment from different suppliers.

Why not take advantage of our specialist expertise with regard to electrochlorination? Our years of extensive experience in working with these systems ensures we are in a very strong position to assess your pool disinfection needs and advise you on the best solution.

What is the Electrochlorination process?

Electrochlorination is the process of applying an electrical current to salt water to produce dilute sodium hypochlorite (bleach) and hydrogen gas. The resultant sodium hypochlorite solution contains between 0.7%-1% chlorine. This low concentration is considered non-hazardous to humans yet still destroys viruses, bacteria, and other harmful microorganisms present in the water, making it safe to drink and preventing the spread of diseases. 

Unlike other chlorination methods, such as chlorine gas or commercial hypochlorite solutions, electrochlorination doesn’t generate any toxic by-products, nor does it require staff to handle hazardous chemicals, such as chlorine or sodium hypochlorite in high concentrations. The only by-product is hydrogen gas and there are processes to manage and disperse this safely.

Electrochlorination is therefore a highly effective and economical technique for disinfecting water. Unsurprisingly, it’s used all over the world, at all scales, from personal electrochlorination units carried by campers in remote locations to giant industrial plants treating potable water for an entire city. 

Electrochlorination produces sodium hypochlorite on site on an “as needed” basis. If required, electrochlorination can function as part of a responsive system that automatically generates a dosage of sodium hypochlorite depending on the existing levels of free chlorine or organic matter in the water. Here at ProDose, we install electrochlorination apparatus ranging in dosing capacity from 25 grams per hour right up to 10 kilograms per hour.

What’s involved in the Electrochlorination Process?

In very basic terms, electrochlorination is the electrolysis of salt water. This can be natural seawater or artificial brine produced by adding sodium chloride, or pure vacuum dried salt, to fresh water. In all brine based systems the incoming water (used to dilute the brine and dissolve the salt) is softened.This reduces calcium and magnesium salts dissolved within the water and prevents the build up of harmful scale deposits around the electrical components and within pipes. This improves the reliability of the system.

After cleaning, the filtered brine flows through a series of electrodes within an electrolytic cell. A low voltage DC current is passed through the solution. At the positive anode, chloride ions are oxidized to produce chlorine. At the negative cathode, the salt water is reduced to sodium hydroxide and hydrogen. The liberated chlorine reacts instantly with the sodium hydroxide to produce sodium hypochlorite, while the hydrogen gas is released. 

The chemical reaction is:

NaCl + H2O + ENERGY → NaOCl + H2

The sodium hypochlorite solution flows onwards to a separate chamber or tank, where it is separated from the by-product, hydrogen gas.The sodium hypochlorite is typically low strength, with a moderate pH value. From here, it can be stored in the short term or immediately injected into the main water system where it goes to work, either as a continuous supply or a shock dose.

Safe Dispersal of Hydrogen

The by-product hydrogen is highly flammable and has no smell. Therefore it should not be permitted to build up in significant quantities around the electrochlorination equipment as it could explode. Some kind of degassing system needs to be built into the process to make sure the hydrogen disperses safely. Prodose advocates the use of dual containment and force air ventilation of all hydrogen containing components within a plant room. This ultra safe method ensures that in the event of a leak of hydrogen (cracked pipe or leaking fitting) the hydrogen is immediately diluted with air to a concentration significantly below the 4% explosive threshold.

Choosing an Electrochlorination System

The ProDose team of experts has specified and installed more than 100 electrochlorination systems in the UK and worldwide. Our experience covers a variety of industries and applications, from food production to school swimming pools to drinking water treatment. We offer a range of AMPRO electrochlorinators to suit every operation, footprint, and budget, and we always include a full after-sale support package.

• MPS Model – A simple wall mounted, lower capacity electrochlorination system, with self-cleaning electrode technology.
• MP Models– Available in three capacities these electrochlorinators feature auto brine dilution, hydrogen degassing and force air ventilation, all in one compact wall mounted assembly. With an intelligent colour touchscreen control panel, operators can access running parameters, help screens and system diagnostics with ease.
• MPI Models – Available in five larger capacities these floor mounted electrochlorinators are supplied fully assembled and ready for integration at site. These also feature auto brine dilution, hydrogen degassing, force air ventilation and intelligent touchscreen control panel as per the MP range.

Call us today to discuss your electrochlorination needs, whether you’re considering upgrading your existing system or installing an entirely new one.

Chlorine Dioxide and Legionella Control

Legionella is a bacterium found in soil and water. When it occurs outdoors, it usually does so in low concentrations and doesn’t cause problems. However, when it grows inside artificial water systems, such as hot tubs, hot water tanks, swimming pools, decorative fountains, or cooling towers, it can multiply to dangerous levels and result in Legionnaires disease in humans. This is a serious form of pneumonia which can be fatal.

There are, in an average year, around 200-250 confirmed cases of Legionnaires disease in England and Wales. Approximately half these cases are the result of local contamination, while the rest can be traced to overseas travel. As it’s a major public health concern, the relevant local authorities must be notified of any Legionnaire’s disease diagnosis so the original source of infection can be investigated and eradicated.

As it’s such a serious health and safety issue, building owners and managers must stay on top of monitoring water supplies for the bacteria and administer treatments as necessary. In the UK, there are very specific health and safety regulations detailed in HSG274. Chlorine dioxide is one of the chemical treatments recommended for making water safe and protecting customers, staff, and residents from Legionnaires’ disease.

Why is Legionella so Dangerous?

Legionnaires disease is spread when people breathe the bacteria in via microscopic water droplets (aerosols), which then infects their lungs and/or respiratory system. It’s not passed from person to person, instead people moving through the same location are likely to become infected at the same time. 

Legionella outbreaks can occur in industrial, commercial, hospital, or even domestic settings, in fact anywhere where quantities of water are stored within the temperature range 30-42ºC. It becomes dormant at lower temperatures, but can revive as soon as the water warms up again. With the right nutrients, the Legionella population can double every 3-4 hours. It thrives in water systems where the usual flow (which disturbs colonies’ growth) is halted for a period of time, such as an office building that has been closed during a pandemic.

Cases of Legionnaires disease can be particularly dangerous in patients who are over 50, smokers, or have an underlying immunodeficiency disorder. Initial symptoms include cough and headache, but this can rapidly progress to chest pains, vomiting, and mental confusion. If left untreated, it may result in respiratory failure, septic shock, or acute kidney failure.

How does Chlorine Dioxide Destroy Legionella?

Legionella bacteria develops inside a protective polysaccharide slime, or biofilm. This layer of microorganisms forms on surfaces that come into contact with water. At even a low concentration of 0.1 ppm, chlorine dioxide penetrates both the biofilm and the bacteria cell walls. It oxidizes the amino acids in the cytoplasm within cells, effectively destroying the bacteria and the nutrients they feed off. Chlorine Dioxide works rapidly and is effective over a wide temperature and pH range.

How is Chlorine Dioxide added to the Water System?

Chlorine dioxide is a volatile gas, which is difficult and potentially dangerous to store. Therefore it’s usually generated on site, as needed, in a stable solution form that is much safer to handle. Chlorine dioxide solution can be derived in a number of different ways, one of the most common is the controlled reaction of low strengths solutions of sodium chlorite NaClO2 and hydrochloric acid. The resultant chemical reaction forms chlorine dioxide (ClO2) and salt and water. As this solution is fresh, precise doses can then be injected into the water system as and where required, so the biocidal action can begin.

The team at ProDose has many years of experience with Legionella prevention and eradication. We can advise you on your level of compliance with the current Approved Code of Practice L8 for control of Legionella bacteria in water systems. We also have a great deal of expertise in designing and maintaining safe water treatment strategies for a variety of buildings, including offices, universities, hospitals, factories, schools, and sports stadiums. We can help you upgrade your existing system or provide you with the latest state-of-the-art equipment. The first step is to give us a call and set up a consultation.

Chlorine Dioxide and Water Treatment for Plant Nurseries

Horticultural facilities, such as plant nurseries, face many of the same water sanitation issues as their agricultural counterparts. These issues include keeping ornamental and food plants healthy, maintaining sanitized equipment, especially irrigation and water recycling systems, and controlling the growth of algae and other harmful microbes.

Treating water with chlorine dioxide solves these problems. It’s also safe, effective at a wide pH range (4-10), and cost efficient for most installations. Finally, chlorine dioxide is odor free, which means it in no way interferes with customers’ experience as they visit a nursery to pick out their plants.

Chlorine dioxide is easy to use. It is a water soluble gas that can be generated on site, as required, then injected directly into irrigation lines. It is an effective disinfectant at a low concentration, below 1.0ppm.

Chlorine Dioxide and Maintaining Plant Health

Most plant nursery owners would agree that keeping plant stock healthy (and therefore attractive to customers) is a big priority. Chlorine dioxide water treatment can be a powerful tool in the fight against plant disease. Even in relatively low amounts, chlorine dioxide added to water can protect against plant pathogens .

For instance, research has shown that chlorine dioxide prevents the spread of Fusarium oxysporum in daffodils during hot water treatment. When used as a dipping agent, it is also effective in reducing Botrytis grey mould in roses. If added to irrigation water, such as that gathered from collection ponds, it kills other pathogens such as Thieloviopsis basicola, Botrytis cinerea, and Clavibacter michiganesis. Chlorine dioxide is effective both if added in small amounts to the regular supply, or as a “shock treatment” at a higher concentration (20-50ppm) in order to target a specific outbreak of a pathogen, or as a periodic cleanse.

Chlorine dioxide is especially useful as a disinfestant as it can be used to control plant diseases during production and post-harvest.

Chlorine Dioxide and Eliminating Biofilm and Algae

The layer of green slime sometimes visible inside a water treatment system is known as biofilm, and it consists of a living mass of organic and inorganic elements that cluster together for survival. Unfortunately, biofilm and the organisms lurking within it thrive on any surface that is in regular contact with water, and that includes the irrigation and return lines, holding and mixing tanks, and containment vessels of typical plant nursery irrigation equipment. Biofilm also grows quickly inside liquid fertilizer lines. If its development is left unchecked, it can block pipes, affecting water flow and pressure, as well as spreading pathogens among plants.

Once again, chlorine dioxide water treatment solves the problem. Once dissolved in water, chlorine dioxide moves freely within the irrigation system. It attacks the surface of the biofilm, destroying it right down to the surface it sits on and, if part of a constant injection system, stops it from re-establishing itself. Chlorine dioxide prevents biofilm regrowth at concentrations as low as 0.25ppm in irrigation water.

Chlorine Dioxide and Irrigation, Runoff, and Water Recycling

Chlorine dioxide can be added to a plant nursery irrigation system with minimal environmental consequences— as long as levels are constantly monitored. When it reacts with microbes, chlorine dioxide does not form any harmful compounds such as trihalomethane, chloramines, chloroform or other halogenated disinfection by-products (DBPs). It dissipates swiftly once water is exposed to air. This means that treated run-off water can continue to circulate within the irrigation system, reducing labour and waste costs. As chlorine dioxide functions as a disinfectant in such a dilute form, it’s not necessary to clean the system after its use with aggressive chemicals, which may corrode plastic pipes and limit equipment life.

If you’re interested in learning more about chlorine dioxide as a water sanitization solution for plant nurseries and other horticultural businesses, please contact the team at ProDose. We have many years of experience in this specific field and can design, install and maintain every element of your irrigation system, as well as supplying all necessary chemicals. Give us a call today!

Keeping It Clean: the use of Chlorine Dioxide in the Food and Beverage Sector

Chlorine dioxide is rising in prominence as the best water treatment additive for the food and drinks industry. It’s powerful and economical, and may be a more practical solution for food-grade facilities than other options such as chlorine or bromine. Chlorine dioxide is also relatively odorless, another big plus for this sector.

What is Chlorine Dioxide (ClO2)?

Chlorine Dioxide is a fast acting disinfectant, used in many different water treatment systems around the world. It’s a yellow or reddish-yellow gas, which breaks down into chlorine gas and oxygen when heated. Chlorine dioxide is quite volatile so it is usually manufactured as a stable solution on site and on demand to avoid some of the issues associated with safe storage.

How is Chlorine Dioxide solution made?

Chlorine dioxide solution can be derived in a number of different ways, one of the most common is the addition of sodium chlorite NaClO2 and hydrochloric acid. The resultant chemical reaction forms chlorine dioxide (ClO2) and salt and water.

Alternatively, a stabilized chlorine dioxide solution can be activated by small doses of a strong acid at timed intervals. This will release low quantities of gaseous chlorine dioxide.

How does Chlorine Dioxide work?

Once added to water, Chlorine Dioxide goes to work very quickly. It remains stable in solution (unlike Chlorine) and therefore remains effective over a wide pH range. It doesn’t react with background organic matter in water (again unlike Chlorine) so it reaches the bioorganisms it’s designed to kill in larger quantities, more immediately.

Chlorine dioxide works as a bactericide, fungicide and antimicrobial agent, eliminating pathogens from the water and from the surface of washed produce. First, chlorine dioxide penetrates the biofilm, the protective polysaccharide “glue” that holds clusters of microbes together. As it doesn’t react with the inert sugars in this layer, it remains at full strength for the next stage. It then works by attacking the microbe’s amino acids and RNA, breaking down cell walls and preventing any further growth.

How does Chlorine Dioxide affect water?

Chlorine dioxide sanitizes water without generating the same environmentally damaging byproducts as its competitors. For instance, chlorine bleach and bromide produce carcinogenic trihalomethanes when added to water. By contrast, Chlorine Dioxide breaks down to water, oxygen and common table salt, making clean-up much easier.

Chlorine dioxide is effective as a disinfectant across a wide range of water pH values. This means it’s suited to the closed loop systems commonly used by the food and drinks industry. When it reacts with bioorganisms, there is no resultant taint or odour – again crucial when washing meat, poultry, fish, or produce.

How does Chlorine Dioxide affect equipment?

Chlorine dioxide is an effective sanitizer at concentrations as low as 5 parts-per-million (ppm). As well as making it environmentally friendly, this means it’s much less corrosive to the stainless steel equipment vital to any food processing or washing plant . By contrast, systems that use hypochlorite solution often operate at much higher residual levels, and at these levels there can often be a detriment corrosive reaction with steels. This leads to extra repair and replacement costs, not to mention down time. Chlorine dioxide is also a very fast acting disinfectant, which makes it ideal for short contact cleaning, further reducing the wear and tear on a water treatment system.

Can an existing water treatment system be converted to Chlorine Dioxide use?

If you have questions about the use of Chlorine Dioxide as a disinfectant in your specific water treatment system, please contact us here at ProDose. Our team of experts have many years of experience with chlorination processes and have installed sanitization systems in many different food and drink production facilities. We’re more than happy to discuss your options, from designing and installing a new system, to adapting and maintaining your existing set up. We also supply chemicals. Call or email us to schedule an appointment to discuss your water treatment needs.