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Natural Swimming Pools using BioNova Technology


Natural Swimming Pools using BioNova Technology

This group is designed to provide information about the worldwide BioNova Natural Swimming Pool activity, benefits of BioNova Natural Swimming Pools, benefits of BioNova Technology, and Natural Swimming Pool standards.

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Latest Activity: Aug 2

This group is designed to provide information about the worldwide BioNova Natural Swimming Pool activity, benefits of BioNova Natural Swimming Pools, benefits of BioNova Technology, and Natural Swimming Pool standards.

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SERBIA--Belgrade (First Residential BioNova Natural Swimming Pool in Serbia)

 The "Hidronova Plus" company of Serbia, headed by Saša Matovic, has installed Serbia's first residential BioNova natural swimming pool in Belgrade. This residential BioNova natural swimming pool was…Continue

Started by John Pustai Jul 29, 2012.

USA--Massachusetts--Nantucket (First Residential BioNova Natural Swimming Pool in the United States) 1 Reply

 The first residential BioNova natural swimming pool in the United States was completed in April, 2012 on Nantucket Island in Massachusetts. This residential BioNova natural swimming pool…Continue

Started by John Pustai. Last reply by Richard A. Falk Jul 29, 2012.

Switzerland--Zurich (Canton)--Dietikon (District)--Schlieren City Public BioNova Natural Swimming Pool

Located in the city of Schlieren in Switzerland is the fabulous Schlieren public BioNova natural swimming pool. This public BioNova natural swimming pool is a testament to how beautiful a BioNova…Continue

Started by John Pustai Jul 22, 2012.

First North American BioNova Natural Swimming Pool Dealer Partner Basic Training Program--August 22-26, 2012, Boston, Massachusetts

 The first North American BioNova® Dealer Partner Natural Swimming Pool (NSP) Basic Training Program will be on August 22 - 26, 2012 in Boston, Massachusetts at the Sheraton Boston. In order to…Continue

Started by John Pustai Jul 22, 2012.

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Comment by Richard A. Falk on November 3, 2014 at 1:36am

Thanks for the info.  Yes, I noticed the stats in detail when I read the report and it was pretty clear that transmission of the disease occurred through multiple methods, but the correlations with the pond usage and water exposure levels did seem to indicate that at least some of the transmission occurred via this rather heavy bather load pond.  The small sample size (and broad confidence intervals as a result) were pretty obvious weak spots, but the genetic typing seemed pretty solid.  Their point, though, was that it demonstrated a transmission mode that could apply to other pathogens in the fecal-to-oral route that aren't necessarily as transmissible via other means.  The following paper is a nice review of this using the CDC surveillance summaries as primary info and shows that the greatest risk is when there is no bulk water disinfection and bather loads are high (Crypto being the exception, of course, since even chlorine doesn't deal with it well).

Where this whole topic came up recently was via a LinkedIn discussion with someone who was very opinionated about NSPs and couldn't even admit that the lack of disinfection in the bulk swimming area water meant that there was no protection of person-to-person transmission of disease except from water dilution (so dependent on amount of fecal release, bather load, circulation, etc.).  They claimed that there have been no outbreaks associated with NSPs and that's when I searched and found that report.

I kept emphasizing that I was not against NSPs, but I was against not being forthcoming about the relative risks even if they are still small.  They would be more like monitored natural waters with their usually low risks except that some of these NSPs including the one in the report appear to be operated at bather loads that are simply too high to count on dilution effects to save the day.

As is pretty obvious by looking at studies such as the one in Pinellas County, FL years ago:

49 pools had no measurable chlorine and many of these or low active chlorine (roughly the FC/CYA ratio) pools had extraordinary bacterial counts, yet there were no reported outbreaks with any of these pools.  So while disinfection is certainly important from a large numbers perspective when dealing with over 250,000 commercial/public pools in the U.S., not having proper disinfection does not mean a high probability of having an outbreak.  A higher probability, yes, but high, no.

That doesn't seem to be true for spas, however, but that's another matter.

As for the MMWR report of the chlorinated pool not preventing transmission, you should note the following statement from that report: "An automated chlorine feeder with stabilized cyanurated chlorine was in use at the pool throughout the day."  That combined with the 0.5-1.0 mg/L chlorine level likely meant the active chlorine level was too low because use of stabilized chlorine builds up CYA (and it irks me that the CDC hardly ever reports the CYA level).  If it were near the max allowed of 100 ppm, then the active chlorine level was equivalent to having only 0.005 - 0.01 mg/L and with a rough CT value for a 3-log kill of 1.3 or so, that would be over 2 hours so a pretty slow kill.  I'm getting the CT value from Table 1 in the following paper:

I've been trying to get the CDC to look at the FC/CYA ratio for years now and perhaps the research agenda for the MAHC will finally take a look at this known science since at least 1974.

Comment by James Robyn on November 3, 2014 at 12:37am

Wow! The resurrection of a 2 year old thread! 

Thank you for bringing up the Nordhessen study - we know it well - note that it dates from 2001 and there have been no followup reports. It does not document the outbreak of crypto in an NSP, it does document and factually demonstrates that an NSP was involved in the transmission of an echovirus outbreak.

The Nordhessen study (I've read it, including the last 3 pages, and have the original German complete report - Echovirus Ausbruch in Nordhessen, August-Oktober 2001”, Staatliches Untersuchungsamt Hessen Zentrum Für
          Gesundheitsschultz Januar 2002)

This was an unabashed attempt by the German Nordhessen Health Department to throw a scare, or create Angst and stop the growth of NSPs in a burgeoning market - preferring that chlorinated vessels be required.

First of all, echovirus is a highly contagious fecal-oral pathogen to which children and young adults are particularly susceptible. It can be transmitted through a variety of means, including airborne particles. It is much more contagious than ebola - it is more like influenza.

In the Nordhessen outbreak report, when one parses the statistical obfuscation, the report documents 15 children and 10 young adults who became ill from the virus. 4 of them had been in the NSP - the rest had not.

We do not dispute that the NSP was involved in the transmission of the disease - however, the report focuses only on the NSP and doesn't also demonstrate that there were daycare centers, donut shops and delivery vans that also could have been involved in the transmission of the disease to the other 21 patients. The recent misunderstanding of science resulting in the political hyperbole about ebola is a great example of how easy it is to scare the public with junk science.

In March of 2002, Prof. Dr. Dr. Hans E. Mueller wrote a critique of the Nordhessen Health Department report in which he analyzed and critiqued all of the aspects of the report including the selection of the control group and the selection of the population of infected patients.

Unfortunately the critique is 11 pages in German and to my knowledge has never been translated into English, but the conclusion is clear.

“The general warning of natural ponds and natural bathing waters as potential sources of Enterovirus infection is a coarse deceit of the public. Bathing ponds and natural bathing waters are much further back on the list of risk factors, all of which the study has left out.  Therefore the study paints a completely distorted picture.” (Translation mine.)

Today in Europe no one brings up the old Nordhessen Report - it's basically been debunked.

And chlorinated vessels also don't always necessarily prevent the transmission of echovirus.

See this link:

The whole point of this is that in my opinion, the public should be free to choose if they want to swim in a chlorinated swimming pool or a natural, chemical-free body of water. Neither can be made totally, 100% safe. It's all about choice.

Comment by Richard A. Falk on November 2, 2014 at 6:32am

(... continued from previous comment)

"In Germany and Austria an increasing number of public chlorinated swimming pools are being rebuilt into nature-like bathing ponds. Bathing ponds generally have an appealing ambiance and offer considerable economic advantages to communities with limited financial resources. However, while in conventional swimming pools chlorination assures a rapid inactivation of introduced pathogens, in bathing ponds water purification is left to natural degrading processes. In swimming lakes dilution effects and water exchange with ground water quickly reduce infection risks to co-bathers following a point contamination. Water volume in bathing ponds is considerably lower."

"Weekly testing of bacterial indicator organisms in pond A never rose above EU bathing water guideline limits. Indicator bacteria are useful markers of faecal contamination only if the faecal contamination results of water influx into a body of water with the water influx containing an average load of pathogens (e.g. from depuration plants, agricultural land wash). If water is contaminated directly by a bather, the relation between pathogens and faecal indicators is
much higher and faecal indicators fail."

"This outbreak demonstrates the potential of nature-like swimming ponds to cause widespread community infection with substantial public health impact. A whole host of other organisms, including hepatitis A, Norovirus and polioviruses are potentially waterborne [25–27]. There is an urgent need to reconsider the popular tendency to convert chlorinated swimming pools into nature-like swimming ponds. Existing ponds need to be promoted with care and require careful maintenance."

Note that since there is no disinfection in the swimming region, you are relying on water dilution to prevent person-to-person transmission of disease. While such dilution can prevent outbreaks in large natural bodies of water, this principle does not work in NSPs with high bather load. The above NSP wasn't that small in spite of what the paper says — 3680 m3 would be 972,000 gallons — though 1500 persons per day even in that volume would be a substantial bather load of around 650 gallons per bather (it's not as bad as this sounds since I'm sure that all these people were not in the pond all day so there probably weren't 1500 people in at the same time).

Comment by Richard A. Falk on November 2, 2014 at 6:30am

James, you wrote the following:

"Interestingly, there has never been an outbreak from cryptosporidium in any of the public NSPs in Europe - and there are over 100 of them in Germany alone."

Well, that simply isn't true. The following paper "An outbreak of viral meningitis associated with a public swimming pool" documents an NSP that has an outbreak:

You need to purchase this article though can get all but the last 3 pages of it at ResearchGate:

I extract the summary (abstract) and selected portions of the paper below for your convenience.

"From July to October 2001, 215 cases of aseptic meningitis occurred among the inhabitants of the German city of Kassel and neighbouring counties. A matched case-control study identified bathing in a public, nature-like pond during the beginning of the outbreak as a risk factor for disease [matched odds ratio (mOR) 44.8, 95% confidence interval (CI) 3.9–515.6]. Among bathers, patients with meningitis spent more time in the water (mOR 18.8, 95% CI 2.0–174.1) and swallowed water more frequently (mOR=7.3, 95% CI 0.7–81.8). Of 30 cerebrospinal fluid samples tested, echovirus 30 was cultured from 16, and echovirus 13 from seven. An echovirus 30 sequence obtained from one pond water sample showed a 99% nucleotide and 100% amino-acid homology with patient isolates. This outbreak demonstrates the potential of nature-like swimming ponds to cause widespread community infection with substantial public health impact."

"Between 13 and 15 August 2001, approximately 10 children and 15 young adults were reported to the health department of the city of Kassel with clinically suspected aseptic meningitis. All had been admitted to local hospitals. Following these reports an outbreak investigation was initiated to identify the pathogen, describe the outbreak, and identify risk factors and possible control measures."

"Kassel is a German city with a population of 195 000 inhabitants. Neighbouring counties are the semi-rural counties of Kassel (246 000 inhabitants) and Go¨ ttingen (265 000 inhabitants). During the hot summer of 2001 bathing facilities and lakes were heavily frequented. In Kassel and neighbouring areas there are two bathing lakes, several public swimming pools and a swimming pond (pond A). Pond A, originally built as a chlorinated swimming pool, was converted into a nature-like swimming pond and reopened in 2001. The rebuilt pond has a total water volume of 3680 m3. Water disinfection with oxidizing substances (e.g. chlorine), as required for public swimming pools, cannot be implemented in nature-like ponds. Organic pollutants are supposed to be degraded through natural processes, mainly through re-circulation of pond water through a planted regeneration area. The pond also included a wading area for small children, including toddlers. During the summer holidays, which ended on 5 August 2001, up to an estimated 1500 persons visited the pond each day."

"We could not definitively determine how the pond became contaminated. Bathing ponds have to be refilled with water of drinking-water quality. Given the small size of the pond, the low infective dose of <=100 virus particles, the potentially high concentrations of virus particles in stool, the absence of efficient disinfection procedures and the high number of visitors, water contamination by faeces of a single person has the potential to cause a high number of echovirus infections."

(continued in next comment...)

Comment by Richard A. Falk on July 27, 2012 at 5:01pm

Thanks James.  Those are good points.  As for the illness rate relative to the bacterial counts, I am calculating those based on the formulas in the EPA document Implementation Guidance for Ambient Water Quality Criteria for Bact....  It is too bad the FLL doesn't use a statistical sampling standard and instead just has a maximum count allowed that triggers investigation but not shutdown unless nothing is found and resampling continues to show exceeding the maximum limit.  The EPA document is pretty good in terms of the statistical nature of sampling and how the geometric mean is most correlated to the number of swimmers who get ill (mostly from gastrointestinal illness).  If you happen to know the typical geometric mean of bacterial counts for the three bacteria in properly managed NSPs, then I can calculate a more accurate predicted illness rate that I'm sure will be lower than the numbers I quoted.

As for Crypto in the U.S., most years saw around 10 outbreaks though in 2005-2006 this jumped to 29 and in 2007-2008 this jumped up to 58.  Nevertheless, out of approximately 300,000 commercial/public swimming pools in the U.S. (vs. around 10 million residential pools roughly evenly split between in-ground and above-ground), the total from 1999-2008 of 122 Crypto outbreaks in treated pools is 0.04%.  So having 100 NSPs with no outbreaks doesn't tell you very much since statistically that is the likely outcome in that small a sample with (1-0.0004)^100 = 96% probability.

That's a good point about the chemical injuries and illness from chemicals.  Though these are most often completely preventable, people make mistakes and the bottom line is the injury rate regardless of human infallibility.

From a bather's perspective, the risk trade-off is between a low (being more generous than my original calculation) roughly 1 in 1000 risk of gastrointestinal illness per swimming season in an NSP compared to a very low long-term increased risk of cancer in a chlorinated pool (though this is more from high bather-load indoor pools) though such risk doesn't show up reliably in epidemiological studies but is theoretically on the order of 1 in 10,000 to 1 in 100,000 over a lifetime based on THM data (it's more like 1 in 1,000,000 for DIN 19643 pools that focus on keeping disinfection by-products low).

Comment by James Robyn on July 27, 2012 at 3:24pm

Two other points that I would like to make.  First, as it relates to the terminology of Natural Swimming Pool (NSP) and it's evolution in German.  Although the Germans started out calling them Schwimmteiche or Badeteiche (see my comment below), today the more sophisticated designs and technological implementations in NSPs are referred to as Naturpools.  In fact, the leading German publication in the pool industry, "Schwimmbad und Sauna" has developed a periodical that discusses NSPs called "Naturpool"

Any my second comment is that one statistic from the CDC that you will never see associated with NSPs, is the illnesses/injuries caused by improper handling of pool chemicals. The CDC has reported that between 2002 and 2008, they estimate that there were 28,071 cases of injuries or illneses from pool chemicals.  Since the NSP does not use any chemicals, they will never be a contributing to this statistic.

Comment by James Robyn on July 27, 2012 at 3:14pm

The term Natural Swimming Pool is a misnomer.  These swimmable watershapes probably should be called Constructed Swimming Ponds.  Because they began in Germanic speaking countries, it's interesting to note what they're called there.  At first they were called Schwimmteiche, literally Swimming Ponds.  Because the German word for a swimming pool is Schwimmbad, the use of the word "Schwimmteich" implied that this was a constructed vessel. Another word which was (and still is) used is Badeteich which means Bathing Pond.

The first major work in English to discuss these vessels was written by Michael Littlewood from the UK.  In his book, Littlewood called them Natural Swimming Pools (the title of the book) - and the name has stuck - probably because it sounds a lot better than Constructed Swimming Ponds.

Several years ago, I wrote a definition of the Natural Swimming Pool or Natural Swimming Pond based on the German FLL Standards.

"A Natural Swimming Pool or Natural Swimming Pond (NSP)  is a system consisting of a constructed body of water, where the water is contained by an isolating membrane or membranes, in which no chemicals or devices that disinfect or sterilize water are used, and all clarifying and cleaning of the water is achieved purely with the motion of the water through biological filters and plants rooted hydroponically in the system."

Today, people in the industry generally refer to Natural Swimming Pools as NSPs.  Note that the definition specifically indicates that the water is not disinfected or sterilized. There is no attempt to imply that NSPs are simply pools that use plants instead of chemicals.  We do however use a catch phrase - "The pool reinvented - Plants instead of chemicals" in our advertising to try to succinctly convey the concept of the NSP, but we never suggest that the water in the NSP is disinfected or sterilized by plants.

In fact, the plants have very little to do with clarifying or purifying the water. Their role in the NSP is to simply remove nutrients from the water and out compete for those nutrients with algae in order to keep algae to a minimum.

Regarding the FLL Standards, the fecal bacteria allowance is not related to a number of ill swimmers per 1000 per swim season, it is specifically the number of coliform units permitted in a 100 ml sample of water.  In the US and Canada, most of the state health departments regulate these levels for public bathing beaches (natural or constructed ponds where the public is permitted to swim) at 200 coliform units per 100 ml of water.  The FLL Standard is twice as strict as that - i.e., FLL Standards permit only 100 coliform units per 100 ml sample of water.  Additionally, the FLL Standards require standards be met for enterococcus and pseudomonas - bacterial standards that are not even addressed in North America.  Finally, in addition to other parameters, like pH, total alkalinity, electrical conductivity, hardness and others, there are standards for visibility.  None of these are addressed by any North American Health Dept for a swimming pond.

Interestingly, there has never been an outbreak from cryptosporidium in any of the public NSPs in Europe - and there are over 100 of them in Germany alone. Germany does have an efficient centralized surveillance reporting system both at the state and federal level and does monitor disease outbreaks. Also, there is a centralized European Center for Disease Prevention and Control (ECDC) that is coordinating reporting data throughout the continent. It is however relatively new when compared to CDC in the US.

Obviously, I am going to agree that NSPs have their place and that it will be interesting to see the statistics once these bathing waters become more prevalent in North America.

Comment by Richard A. Falk on July 24, 2012 at 12:40am

I started a discussion on Natural Swimming Pools (NSPs) in the Water Chemistry group.

First of all, European Directive 2006/7/EC calls these "bathing waters" while German FLL calls them "swimming and bathing ponds".  Neither standard calls them pools and reserves that term (for commercial/public use) solely for disinfected venues.

Also, the levels of fecal bacteria allowed by German FLL is at a rate of roughly 7-10 ill swimmers per 1000 per swim season compared to the EPA swimming pool disinfection standard DIS/TSS-12 that has virtually no illnesses in properly disinfected pools except for the highly chlorine-resistant protozoan oocyst Cryptosporidium parvum.  Most countries in Europe do not have the centralized surveillance reporting system that the CDC uses to keep nationwide statistics for outbreaks so it will be interesting to see the statistics once such bathing waters become more prevalent in the U.S.

The bottom line is that these bathing waters are more like artificial ponds with only somewhat lower illness rates than real natural waters.  They do not have any sort of bulk-water disinfectant at all and therefore do not prevent person-to-person transmission of disease via the fecal-to-oral route -- not for bacteria, viruses or protozoa.  They certainly have a place, but one should be very careful about implying that they are simply pools using plants instead of chemicals.


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