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.