|Effectiveness of Disinfectants on Different Pathogens|
|Microorganism Reduction Ability|
|Chlorine||Very effective||Moderately effective||Not effective||Very effective|
|Ozone||Very effective||Very effective||Very effective||Very effective|
|Chloramines||Very effective||Moderately effective||Not effective||Moderately effective|
|Chlorine dioxide||Very effective||Moderately effective||Moderately effective||Very effective|
|Ultraviolet radiation||Very effective||Very effective||Very effective||Moderately effective|
Note: The reduction levels in the table are
for normal dose and contact time conditions; they are only for
general comparison. The effectiveness of different disinfectants
depends on the dose, contact time and water
Many aquatics professionals are hearing reports about swim meets where athletes have to queue up in the hallway because the natatorium air is too polluted to breathe. Similarly, large indoor waterparks have become the topic du jour on the 5 o’clock news because scores of paying customers claim to have
fallen ill from the air they were breathing during their visit to the facility.
The health issues relating to disinfection
byproducts (DBPs) and indoor air contamination may soon overtake
the concerns about recreational waterborne illnesses (RWIs). A
strong case is being built, supported by studies, that many other
things besides chloramines in pool water should concern us and that
these compounds may cause illness.
First, a few definitions need to be clarified. The
terms chloramines and combined chlorine are not interchangeable.
“Chloramine” refers specifically to monochloramine,
dichloramine and trichloramine, also called nitrogen trichloride.
The term “combined chlorine” encompasses these three
chloramine species plus myriad other chlorinated nitrogen
compounds. The results of combined chlorine wet tests indicate the
presence of many other substances in the water, not just
Some of these chemicals or compounds that show up
as combined chlorine may include oxidants such as potassium
mono-persulfate and ozone. In the absence of these chemicals, the
results of a combined chlorine test indicate the presence of
synthetic organic compounds, volatile organic compounds and other
higher chlorinated ammonia compounds called N-chloro compounds.
Clearly, it is combined chlorine that we should be concerned about,
not just chloramines. Many of these chlorinated compounds do not
yield to breakpoint chlorination.
To complicate things further, it’s fair to
say that pool water chemistry is very poorly understood. To date,
there has not been a single comprehensive study performed on the
multitude of chemical reactions that occur in a pool. Fortunately,
many studies have been performed on the formation of DBPs in
chlorinated drinking water supplies. By inference, we can assume
that most, if not all, of the same reactions occur in pool water
because we typically fill pools with potable water.
It may even be safe to say that a greater
concentration of DBPs is formed in pool water because it contains
more contaminants and a wider range of chemicals. The EPA has
identified and qualified only an estimated 50 percent of the DBPs
that form in chlorinated drinking water. This adds up to
approximately 500 DBPs, most of which have not been qualified as to
their impact on the health of swimmers. The EPA has identified
hundreds of DBPs in potable water, and limited the allowable
concentration there. No equivalent restrictions exist for pool
water in the United States. (See the USEPA Web site at
www.epa.gov/athens/research/process/drinkingwater.html for more
Furthermore, we should not be solely concerned
with DBPs that offgas a pool surface into the atmosphere. Consider
for a moment the immense popularity of indoor waterparks with their
plethora of sprays, geysers, falls and jets. These types of
attractions aerosolize the pool water with its hundreds of
identified and unidentified DBPs, pool chemicals and body
Unfortunately, each and every patron in the park
inhales these minute water droplets. Many operators of indoor
waterparks report air filters clogged with much more than dust.
Some describe the deposits on their air filters as fatty oils and
grease. The sources of these substances are the people in the pool.
Not only are the air filters picking up these substances, but so,
too, are the lungs of the people breathing in the air.
What can we do about it? A good place to start is
modern building designs. While these structures are
energy-efficient, indoor air quality has diminished. The tighter
air envelope within the structure does not permit a building to
“breathe.” Meanwhile, many new buildings feature HVAC
equipment that is designed and installed to bring in very little
fresh outside air. In the case of an indoor pool facility, this
circulation of air contaminated with DBPs and other compounds
exacerbates our problems.
Another point to consider is the design of new
pools. It’s generally accepted that a surge tank in any
filtration system collects the dirtiest water in the pool. In the
case of spraypads, it is the only point of water collection. That
means the turnover is significantly altered when feature pumps are
turned on. In essence, water is short-cycled, resulting in
unfiltered and untreated water becoming aerosolized into the
atmosphere via the features, slides and sprays.
It may be time for codes to mandate that water for
features come directly from the pool. In cases such as spraypads,
where no other water sources exist, an additional filtrate tank
that collects treated water should be required.
It’s also incumbent upon us to carefully
consider the filter types, turnovers, outside air dilution,
supplemental chloramine control equipment and systems controls we
specify and install.
Exciting examples of new equipment are
regenerative media filters; ultraviolet systems that not only
provide an extra disinfection barrier but also DBP control, as
demonstrated by the ground-breaking studies performed by Dr. Chip
Blatchley and Dr. Jing Li of Purdue University; new HVAC system
designs that are efficient, but allow for higher amounts of outside
dilution air to be used in natatoriums; and control systems that
harmonize the functions of chemical controllers, UV and HVAC
systems, allowing the equipment to adjust as a complete package to
accommodate changes in bather loading.
The term “value engineering” also
should be re-evaluated. Too many times, a value-engineered project,
while meeting budgetary constraints, results in “sick
natatorium syndrome,” leading to more discomfort and
Maybe it is time to re-examine how we treat pool
water. Let’s look at the European model. As a general rule,
their equipment selection is geared toward using the best available
technologies and designs. Overall, the equipment for comparable
pools is larger, turnover times are lower, bather capacities are
lower, and operator training is more stringent.
It may even be time to think about how we use
chlorine. Europeans understand that the more chlorine is added to a
pool, the more DBPs will form. The German DIN standard limits the
amount of free chlorine in a swimming pool to 0.6 mg/L (ppm) and a
pH range of 6.5 to 7.6, which maximizes the formation of HOCl.
Taking this concept further, it may be time to rethink the use of
sodium hypochlorite and calcium hypochlorite completely and move to
a different sanitizer/oxidizer such as chlorine dioxide.
Chlorine dioxide is more effective against most
RWIs than chlorine is — especially in the case of
cryptosporidium, as noted in the USEPA Guidance Manual for
Alternative Disinfectants and Oxidants. It forms far fewer DBPs
compared with chlorine and, based on recent toxicological studies
mentioned in Chapter 12 of the Handbook of Chlorination by Clifford
White, previous fears about chlorine dioxide’s principal
byproduct — chlorite ion — have been allayed because of
new generation techniques.
It is clear that we cannot continue with business
as usual. We must ask ourselves the hard questions and take the
bold steps necessary for the health of our industry and, more
importantly, the health of our customers.
Robert Kappel is employed by Siemens Water
Technologies as the Regional Sales Manager for Aquatic Products-
Eastern North America. With over 13 years in the aquatics industry,
his background includes a broad range of experience comprised of
facilities operation, technical service and sales, management,
consulting, large project commissioning and customer training.
Robert is an active member of the International Ultraviolet
Association, holds an APSP Certified Service Professional
designation and is an AFO instructor. Robert is also is the past
co-chair of the Wisconsin HFS-172 Health Code Advisory Committee
and the current Chairperson of the PPOA Board of