Posted By Deirdre Moore
Has anyone got any information about ozone as a substitute disinfectant for chlorine?

I received this query from a Farmer who uses chlorine on his farm and has become allergic to the substance.

If ozone is not suitable, perhaps someone could suggest another substance..

Deirdre

Posted By John Webster
Yes
Ozone is used as a substitute for chlorine in disinfecting water supplies, but hydrogen peroxide is the frequently used altenative to chlorine (hypochlorite) based bleach.
John

Posted By Ken Taylor
Putting the availability and practicality questions aside, you would not want to be caught in an accidental release of either gas. The method and location of application and presence of persons at potential risk will be major dtermining factors. Are you still using Cl2 as a gas rather than Sodium hypochlorite and the like?

Posted By Eric Letherman
Ozone is sometimes used for water treatment in swimming pools and presumably in other situations, too. However, for the reasons discussed elsewhere in this thread ozone doesn't seem particularly practical for your client.

Oxfam use calcium hypochlorite for treating natural well water in developing countries, or areas where the normal water supply has been destroyed or otherwise disturbed to ensure potable water.

As already advised, the reasons for using chlorine need to be established before any alternatives can be considered.

I hope this is of interest.

Posted By Jim Walker
Deirdre,

I've been following this thread with some concern.

With the notable exception of Diane's response can I suggest you ignore most of the other's.
I'm afraid many appear to have a very shaky knowledge of chemistry, disinfectant modes and COSHH requirements.

It is virtually impossible to give you a reasonable answer without knowing more detail.

Posted By John Webster
Yes, thanks Harry and Alex.

I, too, found the tone of Jim's response unhelpful. As a qualified chemist and chemical engineer from a farming family, formerly in water treatment and now working in healthcare in a predominantly agricultural community, I feel I am entitled to reply.

As with so many of these questions, the technical knowledge of the questioner (with all due respect to Deirdre) is often limited - which may well be why the question is being asked in the first place. It is therefore necessary to try and interpret the question rather than just taking everything literally.

12-15% Sodium Hypochlorite solution (NaHOCl) is in common use on farms, where it is supplied in, typically, 25litre drums under trade names such as "Chloros". Its main use is in washing down and cleaning out dairy areas and equipment when it is used diluted with hot water. It is an effective sterilant and, due to its causticity, suitable for cleaning where there is a coating of fats. Given the average person's chemical knowledge and (mis)-useage of the name chlorine to describe any substance giving off a bleachy smell, and given that it is highly improbable that a farmer would use "chlorine" for anything, it is reasonable to assume that the original question almost certainly related to sodium hypochlorite solution.

There was inevitably a response from those, perhaps unaquainted with farming, who naturally did take the use of the word "chlorine" literally. After all, there are plenty of undertakings where liquid or gaseous chlorine IS used, and a nasty substance it is indeed.

Two of those undertakings are swimming pools and water supply, where ozone (as Jay points out, generated in-situ) is now often used in place of chlorine. Again, there is no likely way a farm would use ozone, and so it is much more likely that the substitution issue has been confused and, as Ashley realised, the wrong name used in place of another "oxygen rich" sterilant - Hydrogen Peroxide (H2O2).

Hydrogen Peroxide is a Permitted Disinfection and Cleaning Product for use in livestock buildings under Council Proposal 8697/98 to EC reg. 2092/91: Annexe II E. I believe it is usually supplied as a 20vol 6% solution and in 25 litre drums.

The farmer should, of course, consult with his usual agri-chemical supplier who will be best placed to advise on correct application and use, and on the most appropriate PPE.

Assuming the application is one for which sodium hypochlorite may be substituted with hydrogen peroxide, there are a number of advantages. Hydrogen Peroxide is less damaging to the environment than Sodium Hypochlorite, breaking down to water and oxygen, unlike the latter which forms dangerous chloramines and other chlorinated organic compounds. It is also less irritating to the skin, mucous membranes, eyes and respiratory tract.

There could be a PPE issue here, as has been noted, given the irritant properties of sodium hypochlorite solution. It could also be that the solution is currently being used too strong, again leading to excessive exposure.

Sorry to ramble on, but I hope this gives a full answer to a vague question. If my assumptions are wide of the mark, I apologise. But then, having qualified my response, I would not expect anybody to use information not relevent to their situation.

John

Posted By Ken Taylor
My rhetorical question 'Are you still using Cl2 as a gas rather than Sodium hypochlorite and the like?' was intended as a subtle way of suggesting that the questioner might be using a colloquial term for a liquid disinfectant. However, the offered Ozone alternative is also a gas added to water for disinfection and might, therefore, have also been an exact consideration. The thread seems to have gone in a strange direction on this question.

Posted By Ashley Williams
I Realise this is in a pool environment and not a farm but it mentioned one of the alternatives we previously mentioned.

Council swimming pool chlorine incident
More than 40 persons, many of whom are children, have been treated in hospital for the effects of inhaling chlorine gas at a leisure centre swimming pool in Coatbridge. Dozens more were examined and treated at a hastily created emergency centre in a nearby primary school. Six persons in the neighbouring Buchanan Resource Centre, were also affected and taken to hospital.
Sodium hypochlorite
The major incident occurred shortly after opening time at the Time Capsule in the North Lanarkshire town. Casualties, who in the main were suffering breathing difficulties, were dispersed to several local hospitals.
Investigation will soon reveal the causation of the incident which will be of great interest to other authorities operating such facilities.
Chief Inspector David Stephen of Strathclyde Police reported: "Shortly after 9am a chemical cleaning agent was added to the pool, which caused an almost instantaneous reaction. The incident happened shortly after a lorry driver delivered a quantity of sodium hypochlorite to the pool."

Posted By Ken Taylor
I am aware of 2 cases in schools where a relief caretaker added the chemical to the wrong day-tank and started a chlorine release. However, I have also come across one in which the Ozonators continued to generate after pool circulation stopped and affected an operative within the plant room. Both chemicals have very real hazards and effective controls are called for as part of the risk asessment process. In a swimming pool we recently had built, we were able to provide separate day-tank lean-to buildings for the acid and alkali. Other measures can include non-compatible couplings, interlocks between dosing and circulation and clear colour-coded signage. You cannot assume that the pool designer will get it right. It's always worth checking. On one occasion we found that an interlock depended upon a flow switch which remained in the open position due to the head of water and poor plant room design!