Comment of the Day: Why the Water in Your Naturally Filtered Bayou-Side Swimming Hole Is Going To Be Brown

COMMENT OF THE DAY: WHY THE WATER IN YOUR NATURALLY FILTERED BAYOU-SIDE SWIMMING HOLE IS GOING TO BE BROWN Illustration of Proposed Houston Swimming Hole“I’ll bite. Here’s a very simple engineering analysis. Problems with stream-fed swimming pools in Houston are going to be three-fold: 1) Silt (in engineer-speak, Total-Suspended-Solids or TSS). TSS is treated with sedimentation basins. That can be a large pool (that people don’t swim in) adjacent to the real pool. In water/wastewater treatment plants, a coagulant like alum is usually added to sedimentation basins to make TSS precipitate out quicker. If you’re going to do this with no chemicals, you’ve got to be willing to accept either VERY long treatment times, or only partially successful results. The tiny diameter of the clay particles that make up the TSS in our bayous just flat out won’t come out of suspension without a coagulant, so the water WILL be brown. It’s not necessarily a deal breaker — the water in Galveston’s brown too. 2) Bacteria (in engineer-speak, total coliform count). See here. Usually these are E. Coli, algae, and some protests. ALL streams/lakes/oceans in the entire world have this, even the cleanest and clearest. Realistically, to get an insurance policy to operate, the water’s going to have to be disinfected to some degree. That means chlorination (chemicals), ozonation (chemicals), or UV disinfection. More on UV in a minute. 3) Dissolved oxygen content. You don’t want the water to turn anaerobic. If there’s enough carbon-containing compounds dissolved in the water, the bacteria naturally in the water will eat it rapidly, causing the bacteria to use up all the oxygen that’s already dissolved in the water. This leads to any/all fish in the water suddenly dying off, as well as noxious smells and other really terrible stuff. You can make sure the dissolved oxygen doesn’t drop by filtering out carbon containing compounds (takes chemicals), or using aerators. A dual-way to solve the #2 and #3 issues is by passing the water over a very shallow (less than 6-in. deep) bed of rocks at a fast speed. Think rapids. This lets the water simultaneously re-oxygenate and also absorb huge amounts of UV. This might be the sort of silver bullet that makes this possible in Houston. So: This is going to be expensive, but it’s probably do-able. However, the water is still going to be brown. Sorry.” [Ornlu, commenting on Bayou Swimming Hole Promoters Jump To Kickstarter To Jumpstart Project] Illustration: Houston Needs a Swimming Hole

15 Comment

  • All it would take is one water moccasin or alligator to shut it down.

  • Anyone who gives money to that kickstarter is pretty much just throwing it away.. they could spend $1000 of it, produce a report that says ‘we can’t do it’ and keep the rest easily. Even if they did decide it could work, then what?

    I’d suggest cancelling your pledge and giving to a worthy charity instead, at least the money would be put to some actual use.

  • Not to mention it will quickly become an unofficial dumpster, toilet, and bathing facility.

  • you lie.

  • How brown it will be depends on how much water you’re going to send through it. If you can reduce the flow rate into the pool such that you get a very low-speed, shallow flow of water (think a few inches deep and many feet long), you’ll still get the silts settling out. Add in the probability that the influent will be channeled through a vegetative barrier, perhaps in a gravel bed to increase the surface area to capture the silts, and I think it’s do-able.

    Of course, the gravel bed will fill up over time, so there would have to be a mechanism for backwashing it, which will probably stir up the pool unless it can somehow be captured. But I do think it’s at least worth doing a feasibility study, which was the point of this Kickstarter campaign.

  • I’ll take your word for it that this tome is C of D. I’m not reading all of that…zzzzz.

  • This dude knows what he’s talking about (save for misspelling “protists”).

  • As a native Houstonian who actually swam in the upper reaches of Brays and Keegan’s bayous, I have one question to ask?

    Why on earth would you want to do this?

    We did it because the apartment complexes wouldn’t let us swim in their pools without adult supervision, but even at ten we knew it was disgusting.

  • I don’t get it. They’re going to have to engineer something in a manner such as that it could never resemble both naturally occurring and also something considered sanitary by most of the public; so why not don’t they just drop the pretenses of it being “natural” and just lobby the Parks Department to build a nice public swimming pool?

  • The surface area required to remove that much silt is simply enormous. I don’t know if the city’s water purification plants offer tours for the general public to see this, but the amount of sludge that they export and the amount of flocculation in the water during treatment is very impressive.

  • Yeah, it might be difficult so just quit now and don’t bother your little heads.

  • RoyL: To be like Austin.

  • Something no one has mentioned yet…brain eating amoeba naegleria fowleri. I don’t see how they could prevent this from flourishing in the waters.

  • I’ve got some just as ridiculous ideas:

    1. Lets build a giant mountain downtown and cover it in fake snow and have a ski resort in Houston!

    2. Or lets dam the bayou and create a resevoir right next to downtown ( sorry montrose, downtown, and pretty much all of the western side of houston anywhere near the bayou).

    I’m only asking for 20k for my kickstarter, its a real bargain!

  • My first thought when I saw the rendering above was if you think there will be white sandy beaches with clear blue water you must be high on something.

    There was little doubt in my mind that the beaches dark and the water would be brown. Glad to know someone brought some science to confirm this.