> In 2023, the CDC recommended new health codes that call for "secondary disinfection" methods to keep Crypto at bay, including disinfection systems using ozone or ultraviolet light. Another possible solution is to have "single-pass" splash pads that don't recirculate water.
UV seems straightforward, even as a retrofit — a UV sterilizer is not terribly expensive or large, and it can be installed downstream of the filter without any other complication. (UV works poorly in cloudy water, which is why it goes after the filter.)
Ozone is a mess. The concentrations of ozone that disinfect are also dangerous for people, so you need a “contact chamber” to let the ozone react, and you want to avoid spraying highly ozonated water at children.
It also seems like it might be useful to sterilize the filter every night — those filters can surely end up quite full of cryptosporidium oocysts that will live for a long time. I don’t know what one would sterilize it with, though. Maybe chlorine dioxide?
In any case, IMO the volatility issue is a bit silly. Chlorine is indeed volatile, but chlorinated cyanurates are not, and one can, and should, have cyanuric acid mixed in with one’s chlorinated pool/splash pad water to “stabilize” the chlorine. (They do decrease the effecacy of the chlorine at any given concentration, but they make up for it by making it much easier to maintain an appropriate concentration.) And one can buy a (moderately expensive!) system to monitor and control, closed-loop, the chlorine concentration in the water, so maintaining an appropriate chlorine level in a public pool is not actually that hard.
The real problem here is that cryptosporidium is hard to kill.
I agree, maintaining a pool is super easy. My assumption with the splash pad is that there must be some complication introduced because of the aeration of the water, and maybe the cycle time. Aside from raising the PH, maybe it makes it tough to keep the chlorine levels up even with CYA. I wonder if it would be feasible to build a splash loop that had an intermediate tank which could maintain better control over chlorine levels for a predictable amount of time that would make sanitizing reliable.
Maintaining a pool gets less easy as the amount of gunk added increases in proportion to the volume of water. A lightly used swimming pool? Not so bad. A lightly used swimming pool with an attached spa with spillover? Barely any harder, unless you care about maintaining a nonzero chlorine residual in the hot tub. Residential hot tub that doesn't spill into a pool and gets any amount of serious use? Utterly gross without real effort.
And all of this assumes that you're just not concerned about cryptosporidium. The chlorine levels in a pool do not reliably kill cryptosporidium! So you need something like UV, which will kill it as it goes through the UV chamber.
A splash pad has huge load of junk and a small water volume. The one nice property is that almost all the exposure is to water that is fresh out of the pump and associated filters, which makes UV quite attractive.
Agreed, eliminating crypto in a typical residential pool is basically impossible. If I were sure I had a pool infected with it, I'd probably drain, disinfect as much as possible, refill, and then SLAM the pool hard with no CYA for a while. What a PITA. And that assumes the pool is the type that can be drained.
The most reliable solution, of course, is to screen the people who are going to use your pool and don't allow anyone who has even a hint of crypto symptoms to get in.
I hope that most public pools invest in a UV system. It's hard to prevent some dumbass with diarrhea from deciding today was a good day to swim anyway. Lots of those types of people in the world.
When you first enter the building, you put your belongings into lockers, including your socks and shoes. After some instructions, you walk up a slightly inclined ramp that has a wonderful heated river of water about ankle deep.
I realized this warm river of water was actually cleaning our feet! Shortly thereafter, you enter a room that has a very spongy/pillowy floor, thus drying your feet. To my surprise, the whole process almost gave me an icky feeling. :)
The Japanese take cleaning seriously. The other day I was at a hotel and I saw the hotel front desk staff cleaning the elevator door track late at night.
Their approach to floors and feet is one of my favourite things about Japan. No shoes in the house. No slippers on the tatami. Designated slippers for the toilet. Completely thought out and sane. Traditionally the Japanese life revolves around the floor - you eat sitting on the floor and you sleep on the floor. As such they built very strong processes around maintaining clean floors.
Shoes in the house is insane. Dogs (and humans) regularly excrete on the surfaces you walk on. Studies have found people who drive regularly traipse in lead around the house coming from petrol refilling.
I find the rest of the world's approach to feet and shoes completely upside down. An old roommate explained to me that only after you walk around your home barefoot do you appreciate how clean your floors are and more importantly how clean your feet are.
Conversely, only after you walk around your home barefoot do you appreciate that a critical reason for shoes is because humans created unnaturally flat surfaces to walk and stand on. The best answer is a dedicated pair of shoes for indoor use, but my guess is most people would find that too inconvenient.
That’s the number of cases being directly linked to a specific cause, it doesn’t mean that the actual number was 400/year. It’s like someone trying to estimate how much violence exists from watching the news. You’re likely to see major incidents, but you can only estimate the actual total.
I wouldn’t be surprised if it was well over 10k/year, but the CDC is conservative with their numbers for good reasons.
Also worth noting that there can be incidents where a massive number of people are infected in a short span.
> with the largest sickening over 2,000 water frolickers in one go.
Lots of people experience isolated events of food-borne illnesses for a variety of reasons. But when a restaurant gets 2000 people sick in a short time frame, we shut it down...and correctly so!
The average annual rate is not terribly informative for making effective public health decisions because it smooths out most of the interesting bits.
For public health decisions I agree, but I'm not making those decisions.
For private health decisions (should my family go to a splash pad or not) the average rate, or chance of infection from one visit relative to other activities, would be more relevant.
I wish you luck finding a commercially available filtration system, suitable for high volume recirculating water like a splash pad, that will reliably remove pathogens.
A properly maintained (good luck!) DE filter might do the trick, but they’re messy enough that they’re banned in large parts of the country. Cartridge filters are usually rated at 10 microns, which is nowhere near good enough.
We'll never know if we would have had splash pad filtration if the Iraq invasion didn't happen. What we do know is we were lied to by a presidential candidate and many of our solders were either killed or broken and many many Iraqis died because of that lie. Oh, and greed.
I think we can safely say that splash pad filtration and the Iraq War have no relation and we’d be in exactly the same fecal contaminant situation whether or not we invaded.
After seeing how many porta potties at playgrounds never have their hand sanitizer filled, I have come to grips with fecal matter being a part of the gig
I feel like what the lesson is going to be if it goes to the larger public --> (1) Municipal funds which will go way overboard to try and resolve this - well past any meaningful value and (2) people not using them anymore for beyond reasonable level of concern.
I can't bring myself to be surprised on this? It turns out, animals have default behavior that is just not healthy. Humans aren't specifically bad on this, I don't think?
Excited to see studies on how well different intervention strategies work.
Anything that reduces outbreaks in public spaces is a win, no? Even if they are spaces I am not going to. Even better, if you can reduce outbreaks without necessarily having to change behavior.
Fun fact - well maintained pool water has barely a detectable scent of chlorine. If you go to a pool that reeks of chlorine, what you are really smelling are chloramines. That is the result of chlorine combining with pee and other stuff. It's one of the reasons a poorly maintained pool is so irritating for your skin and eyes.
I sympathize, though, with the maintainers of public pools. A nearly constant bather load comprised mostly of children emptying their bladders at will. It's probably a losing battle. And then periodically one of the little brats will poop in the water. God bless the maintenance guy who has to fish that out and then shock the pool into the safe zone again. Yuck.
It seems like 60 outbreaks over 25 years really isn't that many, with 10K illnesses and 0 reported deaths. As a comparison, every year in the US, over 20,000 children are hospitalized due to the flu, and over a hundred die.
I know the denominator is different - most children are exposed to potential flu vectors, while only some visit splash pads - but I think this article mostly sounds scary because poop is gross.
Pretty sure this is the grossest thing I've ever read on HN!
Chlorination isn't sufficient:
"maintaining germ-killing chlorine concentration is especially difficult for splash pads because the jets and sprays aerosolize chlorine, lowering the concentration.
Still, in most splash-pad linked outbreaks, standard chlorine concentrations aren't enough anyway."
> Another possible solution is to have "single-pass" splash pads that don't recirculate water.
Yeah, do that. Or do ozone and UV and filters and all the things. It is absolutely wild to me that this is in any way surprising to someone. It also did not need the weird descriptions of who has stuck poop where and how it ends up in the water - simply stating that kids inevitable poop in the water is kinda enough to understand the problem.
I never understood, both as a child and now, all the kids that swim in a pool with their mouth open, constantly ingesting and spitting out water. Can you not swim with your mouth closed? Do you have a nasal obstruction?
Well maintained pool water is pretty close to as safe as drinking water, so I wouldn't worry much about relatively small amounts ingested. But at a splash pad with recirculating water, or a popular public pool with a lot of bathers ... yuuuuck.
I clicked on the article to find out what a splash pad was too lol I was still confused for most of it until I realized the first picture wasn't a kid throwing up it was a kid standing on one of those things where water shoots up from the ground, which is apparently a splash pad.
UV seems straightforward, even as a retrofit — a UV sterilizer is not terribly expensive or large, and it can be installed downstream of the filter without any other complication. (UV works poorly in cloudy water, which is why it goes after the filter.)
Ozone is a mess. The concentrations of ozone that disinfect are also dangerous for people, so you need a “contact chamber” to let the ozone react, and you want to avoid spraying highly ozonated water at children.
It also seems like it might be useful to sterilize the filter every night — those filters can surely end up quite full of cryptosporidium oocysts that will live for a long time. I don’t know what one would sterilize it with, though. Maybe chlorine dioxide?