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LA is dumping millions of plastic balls into its reservoir to tackle the drought

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Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#71

Post by redcalx »

rdlecler1 wrote: post #65
redcalx wrote: post #63

Earlier quoted context omitted.

> Black balls will also heat up more, causing more evaporation. Question. Overall, is the heat absorption of the black balls greater than open water? I imagine it's about the same, but perhaps the issue is that the balls are concentrating the heat at the surface, and on the surface of the rotating balls. So it does seem like the evaporation rate could well be higher. I suppose it comes down to the mean rotation rate…

Smart thinking. The balls could be slightly weighted to avoid this issue, albeit this could mean the balls collect a rim of sludge more easily.

> the balls collect a rim of sludge more easily

Not sure if that's a massive issue, that would probably seal the water off even more effectively. That makes me think that this whole balls idea will limit gas exchange too, i.e. much reduced oxygen absorption, but I guess if they want no life in the reservoir that's not an issue.

Overall though I can't help feeling like there are going to be some significant unintended consequences with this scheme.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#72

Post by DanBC »

zz1 wrote: post #46
PhasmaFelis wrote: post #24

Earlier quoted context omitted.

I would guess that having loads of dead algae in your drinking water is not much better than live algae. You want to keep assorted gunk from having a chance to grow in the first place.

But certainly the water is filtered before reaching homes, considering it rests a long time in a open reservoir. So you could remove the dead algae. Still, they certainly have a "better dead" approach, wanting the reservoir to be a dead pool instead of a living ecosystem where they'd have to monitor what is growing and how dangerous it might be.

It's interesting to compare different systems. Here's one for a small part of the UK. Our tap water (from thefaucet) is vety high quality.

http://www.thameswater.co.uk/cycles/accessible/water_treatme...

The last stage of the process is to add chlorine to the water.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#73

Post by WalterBright »

rdlecler1 wrote: post #65
redcalx wrote: post #63

Earlier quoted context omitted.

> Black balls will also heat up more, causing more evaporation. Question. Overall, is the heat absorption of the black balls greater than open water? I imagine it's about the same, but perhaps the issue is that the balls are concentrating the heat at the surface, and on the surface of the rotating balls. So it does seem like the evaporation rate could well be higher. I suppose it comes down to the mean rotation rate…

Smart thinking. The balls could be slightly weighted to avoid this issue, albeit this could mean the balls collect a rim of sludge more easily.

The weighting won't prevent them from sloshing around due to wave action and getting the upper surfaces wet anyway.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#74

Post by thaumaturgy »

Bootvis wrote: post #8

What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use white or reflecting balls so the water stays slightly cooler? I would be glad to know why black balls are chosen.

The primary purpose of these is not to slow down evaporation. In fact they have a negligible effect on the rate of evaporation.

Their primary purpose is to absorb the light spectra that drives chemical reactions in the treated water to prevent carcinogenic bromate from being formed.

Most of the reporting on this, including this article, is pretty bad, and causing a lot of laymen to ask questions like yours, because it doesn't make sense as described in the reporting.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#75

Post by SamReidHughes »

WalterBright wrote: post #73
rdlecler1 wrote: post #65

Earlier quoted context omitted.

Smart thinking. The balls could be slightly weighted to avoid this issue, albeit this could mean the balls collect a rim of sludge more easily.

The weighting won't prevent them from sloshing around due to wave action and getting the upper surfaces wet anyway.

They'd be fine. For example, the tops of these ducks are dry:

https://i.imgur.com/RYyBMrf.jpg

In a reservoir you're not going to get waves that manage to spin the weighted side of the ball up any considerable amount, even if it's only slightly weighted.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#76

Post by erikb »

Implicated wrote: post #31
erikb wrote: post #15

Earlier quoted context omitted.

Now you just said the opposite of what intuition suggests without any evidence, or even argument. Please elaborate and don't just heat up the discussion!

UV + Chlorine = Bromide

Does that look like an explanation to you? I don't see anything about black. I don't see anything about white. I don't see anything about reflecting materials. I see something from chemistry, maybe?

Customer: "Why should I buy the product?" Developer: "Here we had a problem with the inheritance tree. We worked around it with a factory method."

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#77

Post by sauravt »

WalterBright wrote: post #36

I wouldn't be surprised if the balls increased the evaporation rate, for the simple reason that it will increase the surface area of the water (the balls will rotate in the water, bringing wet surfaces up). Black balls will also heat up more, causing more evaporation.

Not if the dye they are using to paint these balls is hydrophobic.

Re: LA is dumping millions of plastic balls into its reservoir to tackle the drought

#78

Post by SamReidHughes »

SamReidHughes wrote: post #75
WalterBright wrote: post #73

Earlier quoted context omitted.

The weighting won't prevent them from sloshing around due to wave action and getting the upper surfaces wet anyway.

They'd be fine. For example, the tops of these ducks are dry: https://i.imgur.com/RYyBMrf.jpg In a reservoir you're not going to get waves that manage to spin the weighted side of the ball up any considerable amount, even if it's only slightly weighted.

Actually maybe I'm talking out of my behind -- what if there was wind? Add more weight then. Obviously a weighted oblate spheroid, like the ducks, would definitely work.
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