bathing in bleach
by Trev Millerswimming pool designer and constructor
and sculptor
and BSc(Hons) Physiology and Chemistry
(University of Sheffield, 1980)
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| bathing in bleach by Trev Millerswimming pool designer and constructor and BSc(Hons) Physiology and Chemistry |
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page contents
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This document is at wavesculptor.com /pools/chlorine_diatribe.htm. | |
This is a page about general pool sanitisation. My living swimming page and technology page contain information about my own pool hygiene systems based on natural water ecology.
This page started life essentially as a way of isolating, from the pages about my own pools, my rants about the various state-of-the-art pools that I regularly swam in as a youth, and their effect upon my wellbeing. My indignation has served swimmers to some extent in that it has inspired me to create and develop a particular kind of pool that is other than a natural "swimming pond" or a hospital-like "swimming pool".... Swimming ponds tend to be entirely rustic in appearance and operation, relying upon little more than the incidental effects of plants in an aquatic environment to maintain an indeterminately-robust standard of hygiene best suited to occasional, seasonal or limited user applications. At the opposite extreme are large municipal or commercial pools, catering for continual frequent, heavy loads of bathers of indeterminable hygiene, in warmer water, by using sophisticated "industrial" sanitisation.
Since I began this page, concern about the undesirable effects of chlorination has become mainstream(13), and knowledge of how to optimise its performance has become more widespread. My response is to bring to this page rather more open-mindedness than before, which might help potential pool builders visiting this web site to evaluate which kind of swimming water sanitisation is most suited to their project, recognising that all the options have a niche somewhere, but probably none of them everywhere. While much of this page still describes the chemistry of chlorine, which is still the most popular pool sanitiser, the later paragraphs give links to some other sites giving good accounts of some mainstream alternatives, as well as my own. My personal interest in swimming water hygiene management involves the synergistic use of: rapid and selective water-turn-over; higher aquatic plants and their commencal micro-organisms; and biologically active filtration. I began my investigations here from the principles of reed beds as pioneered by Kaethe Seidel(11) in Germany in the 1950s.
Sanitisation has become the preferred term to describe the maintenance of swimming water hygiene. Since the pool cannot be isolated from its surroundings and users, it cannot be sterilised. Even disinfection is too rigorous a term to apply to what can be reliably achieved in a pool. A best case is sanitisation which reduces - but not eliminates - the various potential pathogens in the water to less than legally specified limits.
Without effective sanitisation, swimming pool water, particularly pool water with large numbers of users, is a choice method for the transmission of many human infectious conditions. However, sanitisation by means of established processes involving molecular chlorine and its derivatives should be considered controversial since association of disinfection byproducts with longer term health and environmental risks. The discomfort resulting from bathing in a chlorinated pool that is anything less than perfectly managed would in itself suggest that other equally - or more - effective methods of sanitisation deserve further development and promotion.
Free chlorine is so aggressive that it rapidly reacts with almost any biological material around it to form byproducts, including some giving cause for concern. The action of free chlorine is so broad-spectrum such that, as the concentration of it and time exposed to it increase, it becomes progressively more - but not equally - acutely toxic to all known organisms, without exception. For all but the last few years of the history of the chlorine industry which began with the production of gas for use as a weapon in World War I (12), it has been accepted that most toxicity of chlorine is manifested acutely in the lungs, and then only at concentrations much higher than would be encountered around swimming pools. Whilst the lungs are where most immediate life-threatening inhalation damage occurs, the references against the data, below, on chlorine toxicity and doses, indicate this is not the only case. Some of the data below refer to concentrations of free chlorine in air, and some to concentration in water. If water containing dissolved chlorine is acidified such as when chlorinated water is swallowed, the chlorine contained in the swallowed water will be immediately liberated - within the body, in the case of swallowing.
Humans are not endangered by the concentration of chlorine that rapidly disables many isolated micro-organisms. The ability of the HOCl solvation product of chlorine to easily diffuse through most exposed cell walls in a few seconds, disrupting vital functions taking place very close to the boundary with the chlorinated water, means chlorine disables micro-organisms in seconds by denaturing their enzyme proteins. The complete oxidation of the cell and contents takes much longer. The fine tuning involved with the use of chlorine is maintaining a concentration that kills isolated cells within a few seconds, but that does not make a significant number of bathers become discernibly and attributably clinically ill from its effect as well. Since the volume to surface area ratio of the human body is much larger than of a micro-organism, and our blood and vital organs relatively deeply buried in less vital tissues which can intercept chlorine diffusing in directly from the water, we are not as severely affected. Our exposed mucosa are most vulnerable, particularly eyes and airways, protected only by the secretions covering them, their ability to buffer changes in pH and to regenerate quickly. Humans risk injury from chlorine or its byproducts mostly by inhalation of concentrations of that overwhelm our defenses.
Micro-organisms can, however, survive much longer in pool water in clumps surrounded by protective dead matter, or protective mucous, or in surface films. In chlorinated pool water with a slow turn-over, pathogens protected in these ways may survive for long enough to be ingested by humans. The pathogenic micro-organisms Cryptosporidium sp. and Giardia have relatively impermeable walls allowing them to survive chlorine at the concentrations permitted in public pools for long enough to risk ingestion.
End products of chlorine disinfection are ideally harmless solvated ionic chlorides - an important component of our bodies, like for instance, common salt: sodium chloride, from which chlorine is manufactured. But there are many other products of chlorine disinfection, some of which are hazardous, including the following.
A recognised advantage of chlorine or chlorine-bleach as a pool sanitiser is that as well as immediately killing most micro-organisms in the water at the point where it is added, part of any dose of chlorine will remain latent in the water and continue to sanitise over the period of time that the pool water takes to circulate, ensuring an aggressive environment in any circulating region of the water system. The effectiveness of this sustained action, however, is determined by many factors which pool operators will not always maintain sufficient control over. For a chlorination system to perform as effectively as intended, automation is almost essential, and even then cannot maintain the system efficacy if other factors in the pool management regime are not carefully attended to.
Chlorine-bleach is popular with private pool operators because any vessel with some sort of recirculation system and filter can be kept looking cleaner than without chlorine, and thus more attractive to swimmers, without any capital expenditure, and with minimal understanding of pool management. This is because, besides actually sanitising the pool, the chlorine does actually bleach organic suspended matter, surface contamination and sediment and break them down into less visible soluble and volatile substances, facilitating a tidy, defined look to a pool; with continuously maintained concentrations such as used in public pools, chlorine is also toxic to algae, thus preventing the "murkiness" caused by their growth. If these effects of chlorine are required without chlorine, other carefully designed systems are needed.
Should pool users accept discomfort and mild, almost unattributable inflammations, and the small risks of long term effects from chlorination byproducts as the cost of the prevention of more frequent outbreaks of traceable, serious infectious illness? A high proportion of bathers in chlorinated pools are probably young and robust. I am still a keen swimmer but during the latter half off my life (I was born in 1957), I have weighed up my reactions to swimming in chlorinated pools and inevitably decided not to subject myself to the consequences (see next section). How many potential users besides me do not use such pools because of experience of their unacceptable side effects? Can statistics of the efficacy of chlorinated pools be made to take the former into account?
Public pool operators are obliged by public health requirements to cover themselves using the most established means. Private pool operators like chlorine for the reasons given in the previous section. Unless they are promoted, subtler non-commercial processes will not be seen as part of the picture. Like most products that are established in the market place, there is - literally - a strong investment in keeping chlorine at the top.
But now, entering the mainstream swimming arena from the backwaters where they have been for years, are a variety of commercial products designed to augment pool hygiene, or reduce the concentration of chlorine necessary to achieve any standard of hygiene, or even in some situations replace chlorine. Synthetic chemicals designed to optimise or reduce chlorine dependence include algicides, stabilisers, pH regulators, softeners, and sanitisers such as bromine derivatives, hydrogen peroxide and quaternary ammonium salts, polyhexamethylene biguanide (PHMB) - marketed as Bacquacil®. Treatments which are at least as reliant on "equipment" as consumables include include electrolytic copper and silver solvation17, chlorine dioxide generation16, electrolytic in-situ chlorine generation relying on saline pool water, ozone disinfection, ultraviolet disinfection, and activated carbon or mineral filters claiming to reduce the amounts of chemicals you need. All of these products have some things in common: they are specialist manufactured items which consume energy and require considerable expenditure, capital or specialist maintenance, and do not regulate or regenerate themselves. Most are not as effective as chlorine, but other than their less aggressive in-your-faceness, they have a lot more in common with the use of chlorine bleach than a natural system, as they provide no tangible benefits other than sanitising the pool water.
Whilst I am able to describe my own(18) alternative that appears to be working in one environment, I realise that this alternative is neither appropriate for all swimming pool applications nor ready for public pools without much further development. My main objective in writing this document is to campaign for an "attitude" to water hygiene, rather than one specific solution. That attitude is to embrace the young, productive science of biomimicry(14) rather than the hard (hard-edged and hard on people and the natural environment) technology of military industrial assault.
In my teens and twenties, I used to swim at least once a week in chlorinated public pools. Eventually I had to stop this because the effects on me were becoming intolerable, though I assumed this was my problem and complained to no-one likely to scientifically record my grievance. Whilst actually swimming hard (wearing goggles), the adrenalin of exertion would suppress my inflammatory response to the chlorine (or nitrogen trichloride), but upon leaving the pool, it frequently lead to sensitisation to airborne pollen and other irritants, and nasal and throat infections, which occurred less when I did not swim. I must therefore attribute such acute ailments either to the damage to my body's protective systems due to the chlorination system as well as to any micro-organisms, smoke or pollen there to exacerbate the damage, or entirely to the failure of chlorination to control infectious agents in the pool water leading to such sensitisation.
Whether all the public pools I used in my youth (in the 1960s and '70s) were badly managed or not, a mild to strong odour of chlorine (or nitrogen trichloride) was present around them all. One indoor pool I regularly swam in was on a route I integrated with my work, so I would frequently enter the building but decide to carry on with my business without stopping for a dip, because the fumes would be too disturbing. Whatever the regimen maintained at the pools, it was such that I almost always came away with my eyes and airways feeling mildly to distressingly inflamed, and almost incapacitating abdominal discomfort if I accidentally swallowed any pool water.
My work as an electronics engineer, at that time, also involved me in regular exposure to chlorinated solvents and fumes from heated PVC. I now rarely encounter such pollution but I remain susceptible to a number of immune disorders that are becoming higher profile in contemporary society, particularly allergies, arthritis and depression. In my 30s, I brought myself back, with no medical intervention, to remarkable fitness and health from a state of severe joint inflammation and deformity, impaired mobility, and pain, mainly by means of extremely careful diet.
My investigations into ecological pool management are based on the way living organisms have together been regulating the nature of the planet's biosphere - its surface, oceans and atmosphere - for many times longer than humans have been around. Inhabitants of ecosystems, including aquatic ones, have often evolved ways of biasing their environment towards states in which they can function better, and frequently do this symbiotically between micro-organisms, higher plants and animals.(14) Chlorination is unlikely to be compatible with sanitisation by means of living organisms, as the organisms effecting the sanitisation may be compromised if not killed by the chlorine as well as potential pathogens, though this has not been tested. Seidel(11) and others have, however, demonstrated that some aquatic plants are actually able to metabolise and destroy organochlorines, perhaps even deriving nutritional value from them.
In the swimming pool environment, my aim is for a large volume of water of near drinking quality, as being swallowed is in effect what will happen to a minute but ultimately significant proportion of it. The systems I have used to try to obtain this are explained on my El Valero pool(18) pages.
...lead to my belief that a more aesthetically and environmentally acceptable way forward in swimming pool water hygiene management involves the synergistic use of:
Though biological pool water quality management is at a very early stage of development, I suspect that in less than a generation, the consensus will be to reject the concept of jumping into an aggressive chemical soup like this writer frequently did in his youth.
It will be clear to you if you explore other sections of this site that I am an artist as well as engineer and scientist. If you are an individual or represent a public body which wishes to support the development of biological swimming pools incorporating creative sculptural architecture and leaving a unique natural swimming pool as a product, then do .
Creating and maintaining a page such as this is an arduous task for an individual. Statements I have made or references I have given may be controversial or out of date. If you would like to support a criticism (with your own internet references traceable to reputable sources) which you think warrants a modification of this page, please don't just skip by and discount it: you can easily contact me with your response. Thanks.
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| this site ©2001-2005 Trev Miller aka Val dolphin
Page history: Original page: 2003, November 11th New content page: 2005, January 16th Last minor mods: 2005, Dec 24th |
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