Why does Chlorine Dioxide Beat Chlorine Every Time?

28 June 2017

By Kirsty McLaren

Can we continue to rely upon chlorine to treat water effectively and if not, what are the alternatives?

Companies are beginning to look for alternatives to chlorine for a variety of factors, and are now looking to Chlorine Dioxide as a more preferable and more effective biocide. Scotmas is a water treatment technology specialist with over 30 years’ experience studying the uses and reactivity of Chlorine Dioxide (ClO₂). The company has been in the forefront of innovation to design, manufacture and install water treatment generators where to date, they have helped to treat water in numerous low to large scale projects across the globe.

Below, you will find four key motivators to use Chlorine Dioxide:   

Cost Efficiencies

It is important to compare and analyse the chemical properties, and kill efficiencies of both chlorine and Chlorine Dioxide, which provides us with a far better overall understanding of what biocide can give businesses a greater return on investment.

Chlorine Dioxide has a low oxidation strength and so, the biocide is more selective in what it reacts with. In addition to ClO₂ having greater specificity in relation to what it reacts with, it has a higher oxidation capacity, which means that it has the ability to sustain more reactions. This is possible as ClO₂ has two and a half times more electrons to give than other biocides, such as chlorine and so, gram for gram, has the capacity to react with and destroy 2.5 x more biological contaminants.

Not only does chlorine get used up far quicker due to having no specificity in what it reacts with, but microorganisms can build up resistance to chlorine, hence it is a greater economic risk to invest in chlorine as a biocide.

Therefore, it is clear that if chlorine is used, expenses will be greater as more Cl will have to be added to the water to kill all harmful contaminants. 

Better for Health

If we look at the core fundamental strategy of the Healthcare industry, it is to protect the welfare of the public. What many are not aware of, is that water supplied to hospitals, care homes and similar healthcare environments is often treated with chlorine. We are highlighting this, as chlorine can react with precursors and as a result can potentially produce trihalomethanes (THMs), which are carcinogenic by-products and a potential health hazard. In comparison, Chlorine Dioxide cannot produce THMs due to the fact that it is an oxidant i.e. it oxidises other microorganisms and elements, and it converts back to a chlorite ion i.e. ClO₂⁻, which is stable in water and harmless to humans.

A great benefit of treating drinking water with ClO₂ is that you do not get the chemical aftertaste of chlorine, experienced by many of us that drink tap water.

ClO₂ also targets microorganisms by reacting within the cell wall, hence deactivating and destroying the entire cell. Chlorine Dioxide has also been proven to destroy inactive microorganisms, which if allowed to become active can be potentially harmful. Microorganisms in drinking water can include Cryptosporidium, Cholera or Giardia and these microorganisms cannot develop resistance to ClO₂. Chlorine on the other hand reacts on the cell wall, hence having a slower kill time.  

 Chlorine V Chlorine Dioxide 1

Biofilm Destruction

Another key property of Chlorine Dioxide is that it can destroy biofilm at source, unlike chlorine which biofilm is resistant to. Biofilm formation is a health and safety hazard, as well as being detrimental to business success through increased expenses when it builds up in the pipelines. Within biofilm, you can often find Pseudomonas or Legionella, which cannot only result in corrosion through the pipework and energy inefficiency, but can also cause Legionnaires Disease if not treated or destroyed. Adhering to L8 regulations is crucial, particularly for businesses in the Building Services and Facilities Management industry.


Graphic of Biofilm in Pipework


Chlorine Dioxide is effective across the entire pH range, as it lacks significant reactions with water. This is not the case for chlorine, where its effectiveness is very much pH dependant. When chlorine is added to seawater (norm is pH8), the chlorine converts to a hypochlorite ion, which is inactive and so, ineffective at killing microorganisms, this is known as chlorine disassociation.

Contact Scotmas today for a consultation on our Chlorine Dioxide solutions, and our dedicated team of chemical and project engineers will be more than happy to answer any queries that you may have. 

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