chloramines in your swimming pool

Alan Lewis, pool consultant from Aquazure, investigates the issue of phantom chloramines, and concludes that yes, you should be scared of ghosts.

Confusion is rife over the issue of testing for chloramines in swimming pools. Definitive testing of chloramines is critical in public indoor pools, because combined chlorine is the real enemy of good disinfection. Aquatic centres invest a lot in minimising chloramines, since they are the precursors of vital health concerns. Examples of these are the gaseous trichloramines thought to aggravate asthma, or trihalomethanes (THMs) which, when absorbed in the blood of swimmers and staff, could be carcinogenic. In several states in Australia the guidelines or regulations limit the presence of chloramines in indoor public pools to 1.0mg/L, yet heavily frequented pools are constantly battling to meet this requirement. The most common practice for the reduction or destruction of chloramines used to be “breakpoint chlorination” – where the indoor pool is super-chlorinated at a rate of 10-times the chloramine residual. This practice is great for chemical manufacturers but almost impossible to apply in our modern day aquatic centres which open early in the morning and close late at night – leaving insufficient time to treat the pool and allow it to return to the normal disinfection level by morning. The great advantage was that this procedure was very effective in maintaining a perfect state of disinfection. Hence, for example, the cryptosporidium protocol current in many states requires a similar approach. In other parts of the world, it is required to add 30L of fresh water for every bather. Heated pools find this very demanding on their energy bill because the fresh incoming water from the mains must to be raised to the normal temperature of the pool overnight. Now that water shortages are rife in most states, this too has brought added stress to the way we use, recycle or dump water. Dilution remains one of the most effective solutions.

 A raft of new demands and thinking about ways to control chloramines and other Disinfectant By-Products (DBPs) in public indoor swimming pools has arisen. UV; radiation; ozonation; and chlorine dioxide are among these, even though they are very costly to install and maintain. Lately, many European countries have been changing their regulations to allow maintenance of lower residuals of free chlorine (eg Italy: 0.6-1.2mg/L). The New South Wales Health Department (1996) agreed that ORP (Redox Potential) can be used as a criterion for the maintenance of disinfection, thus releasing pools from the normal requirement for a constant residual of “free available chlorine” (FAC). All of these solutions have their downsides – but are in effect prompting us to rethink our attitudes to treatment and maintenance of public recreational water. Most disconcerting of all is the unresolved matter of just how to test for the presence of inorganic chloramines and THMs, and whether all or some of the tested chloramines aggravate, dissipate or are ignorable health issues.

 Two types of chloramines

Over the past few years, a spate of discussions in US pool management literature has questioned the way we should relate to the presence of chloramines. Naturally, many operators are anxious to accept excuses for avoiding concerns about chloramines by defining them as “harmless chloramines” or “ghost chloramines”. They are in fact relating to the chemical definition and properties of Organic Chloramines. Let us take a pause here to understand just what this field of chemistry deals with. Nearly two hundred years ago chemists noted that the majority of compounds they found in nature, could only be made by living organisms (animal or vegetable) and all included carbon (C). As the science progressed, ways were found to reproduce these compounds artificially. So organic chemistry is now often called Carbon Chemistry. Inorganic chemistry is here fore a study of compounds which are made up of all the other elements. This definition has become somewhat clouded by some alternate ways of categorizing the two chemistries. Thus many schools often find that there is a considerable overlap between the two. This has confused the discussions on the internet too – particularly by purveyors of chemicals – resulting in the misleading of readers with some misconceptions. Let us keep our discussion simple:

The Inorganic Chloramines we are concerned with in swimming pools are:

• Monochloramine NH2Cl

• Dichloramine NHCl2

• Trichloramine NCl3

Note that none of these include carbon.

 These are quite stable, hang around in the pool for a long time, and are easy to test in the field (as a group). They are also relatively easy to identify in the laboratory.

 
Research of organic chloramines

Organic chloramines are difficult to enumerate here and also difficult to test when in the presence of inorganic chloramines. There are no known field tests for organic chloramines and they are grouped together under the general form: RNHCl. The R relates to any one of dozens of organic side chains with Carbon as the primary component; such as Methane (CH4), or Ethane (C2H6). Body amino acids have been well researched and each has its specific function in our metabolism. This group concerns us, because they are prominent in the make-up of chloramines in pools. Among these is the group known as trihalomethanes (THMs) – which are considered potentially carcinogenic.

 Their biocidal activity in a pool is insignificant and can be ignored for all intents and purposes. However we do recognize that they will show up when we test for inorganic chloramines with DPD 1 + 3 or DPD 4 (the test for total chlorine). In the laboratory it is possible to separately test for the group RNHCl (organic chloramines). Disagreement arises with methodologies for differentiating between the two types of chloramines. The organic types easily interchange and are very unstable – so the test must first stabilize the contents. If the sample has been chilled soon after it has been taken, then there is a chance of getting a reasonably accurate picture in the lab, provided that the process of testing is fast enough to beat an interchange. The expensive and involved attempts made by Lucasewycz et al (1989), were the closest that reputable scientists have got to differentiating between the two types using both ultraviolet and electrochemical detection.

 To confirm the disinfection efficacy of organic chloramines, Donnermair & Blatchley (2003) ran a thorough study of 20 body amino acids and two nucleic acid bases. They prepared solutions with a molar ratio of 0.4:1 (Cl:N) to investigate how well these organic chloramines can inactivate E. coli in suspension over 60 minutes. All of them, with the exception of Proline, showed little effect on the viability of E coli. The interesting part is that the worry about interchange-ability between these particular acids and inorganic chloramines was unquantifiable. In this case the researchers used a mass spectrometry device for the detection of the inorganic chloramines. Today, this method is generally considered to be very reliable. So the jury is still out on interchange-ability.

 In this research only a few of the amino acids did not combine with all the free chlorine (note the ratio above), leaving a measurable free chlorine residual after the 60 minutes test period. The  degeneration of the inorganic chloramines uses up a lot of chlorine which would otherwise be better utilised as a disinfectant, sotherefore it is immaterial whether the chloramines are inorganic or organic. They still grab a lot of the free chlorine for their own gratification – thus detracting from its work on the pathogens in the water.

 One can only draw the logical conclusion from all this research that, for the purposes of this  iscussion, the quantitative identification of organic chloramines in swimming pools is really quite

irrelevant. On average, an hour of activity in the swimming pool produces 200ml sweat and 50ml urine, at a temperature of 28 – 30 °C

(Judd & Black 2000).

Sweat is rich in Ammonia (NH3) and it quickly combines with the free chlorine (Hypochlorous Acid -HOCl):

Note that no trichloramines develop here – the nitrogen “gases off” harmlessly into the air.

 Of course it is the Nitrogen Trichloride (or trichloramine) which we are trying to avoid. This is the smelly gas that irritates the eyes and the mucous membranes – and in some cases aggravates the lungs of those suffering from asthma. Apparently ozone may act as a catalyst in this reaction.

 
What you don’t know may do you more harm than good

Some of the worst aspects of chlorination are of great concern because they are rarely identified. These are often the ones we choose to ignore altogether:

 A) Phantom (or Ghost) Free Chlorine:

You will have noticed that equations (i) – (iv) are reversible. If in any of these cases you happen to take a sample and are testing for Free Available Chlorine in the field – you might wonder why the residual and the ORP reads lower than expected. Let the test stand for several more minutes and you might notice the colour deepening in the tube giving a reading much higher than the original one.

 If this is the case you can be reasonably sure that there is a lot of ammonia in the water which has bound up with the chlorine. By letting the test tube stand you have allowed the water to cool (relative to that in the pool). When that happens the pH will slowly decline, resulting in a rise of the FAC (and the ORP). The “phantom” will have returned to base! Yes, pH is temperature sensitive. When chloramines are around, these demanding types are always looking to grab more chlorine – unless you know how to trick them by cooling the water a little.

 B) Phantom Chloramines

To the best of my knowledge this term is an “American invention.” The chemical explanation is reasonably simple. Perhaps the unidentifiable chemical is an organic chloramine which has formed from hydro-carbons introduced into the water from beauty lotions applied by the bathers before entering the very warm water of the pool or spa.

 The second common reference to ghost or phantom chloramines has been described as an attempt by the operator to placate the patrons that “.. since there is no smell in the room – the chloramines must be organic – and they don’t count”.

 C) Trihalomethanes

Earlier I mentioned that the worst enemy of the lot is the presence of trihalomethanes (usually chloroform CHCl3) in the pool. The test for these is also extremely complicated. Nor is the cost of such testing likely to be met by the average aquatic centre struggling to keep the facility viable.

 Here at least the research is absolutely clear. It has been shown repeatedly that further oxidation of the chloramines can result in the development of single-carbon compounds known as Haloforms. These compounds are formed by the substitution of a halogen such as Chlorine; Bromine or Iodine; in a single-carbon compound. Chloroform (CHCl3) is the compound most commonly found in pools treated with Sodium or Calcium Hypochlorite, in conjunction with UV radiation. Furthermore, since many potable water systems involve chloramination and UV or Ozone, health authorities worldwide are limiting the amount of THMs allowable due to its proven carcinogenic potential. Small residuals can be very potent, even though they are hardly noticeable. DIN (19643) and FINA standards set the limit at 200 micrograms per cubic meter (μg/L-1 ) in the air above the pool, and 20 micrograms per litre in the water (μg/L-1) some ten years ago. It should be noted that THMs are taken in by three routes: ingestion; inhalation; and dermal absorption. THMs in indoor pools have been shown to increase with the bather load. In other words, the more chloramines and bathers there are – the more THMs are likely to be produced. The dermal absorption path appears to be the one of main concern. The implication is that the amines exiting through the pores of the skin react with the free chlorine well inside the outer layers of skin, thus shortening the path to the bloodstream.

 Ozone studies

One study carried out by Sydney Water in 2003 showed that a suburban hotel pool treated with low level ozone continuously over 10 weeks, actually reduced THMs from 589μg/L-1 to 277μg/L-1. This

was one of the rare occasions when funds were found to conduct expensive longitudinal tests involving one of Australia’s world renowned independent research laboratories. The impact on our recreational pool industry was minimal and this stunning result passed almost unnoticed in Australia. It should also be noted that these levels (of THMs) are extremely high compared with other international research results over the last five to six years.

 UV studies

The production of THMs in pool water treatment involving UV radiation has brought some alarming results. [Please note, this is NOT the type of UV used in ozone production.] While UV does reduce

trichloramines effectively, in doing so, it has been found to increase the formation of THMs. Black (1999) noticed a short lived increase in THMs after treatment with UV and this was confi rmed by later similar studies in Cranfield University.

 The most recent and startling findings come from Montpellier University (Faculty of Sport Sciences) in France (Cassan et al June 2005). They assert that THMs significantly increase when medium pressure UV lamps are functioning in the treatment system of indoor public pools. Note that the maximum allowable level of chloramines here is 0.6 mg/L while there are no guidelines in Europe or Australia for THM levels. The mean results (μg/L-1) were spread over 4 weeks where for the fi rst week the UV was off. Wk1: 36; Wk 2: 95; Wk3: 75; Wk4: 76. This indicates that by week 3 a steady state (Also found by Judd and Black 2000) of THMs had been achieved.

The researchers chose WHO (1993) guidelines for drinking water which allow 200μg/L-1 CHCl3 as the limit. But further studies would be needed to ascertain the impact of inhalation and absorption of CHCl3 and other THMs, into swimmers’ and staff’s blood, beyond the ingestion route.

 In conclusion

In summarizing this discussion, the important facts to remember are that the more chlorine and bathers there are in the pool together, the more chloramines are likely to be formed. One thousand

swimmers will produce on average a total of 250 litres of body ammonias which will promptly react with the free chlorine in the pool. Dealing with this is difficult and fraught with insidious side effects.

Any system which produces water which can kill the bugs quickly with a minimum of chlorine is going to be more effective. Low level ozone appears to bring better results than UV if we rely on the latest literature. Clearly we need to take advantage of more advanced technological solutions which use less chemicals – low level UV radiation or ozonation – and yet achieve maximum protection from infection.

 There is also the new DiaCell system, a process which uses low level residuals of sodium chloride for an electrolytic disinfection process which relies on Boron Doped Diamond (BDD) electrodes and produces a line of hydroxyl radicals. Solutions to some of the dilemmas presented in this article might possibly be found with that process.

Extract from February/March 2007 edition of SPLASH pool & spa industry magazine