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Comment by DanBC | Hacker News Reader

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> And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating. In the reservoir water, the naturally occurring bromide was mixing with sunlight and chlorine (added to disinfect drinking water) to create dangerous levels of the the carcinogen bromate. Shade balls should stop that harmful chemical reaction from happening at a large scale, and of course by deflecting the Sun's rays, they also keep more of the water in liquid form.

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Well, there is a difference from "we do this" and "we have been mandated to do this", whatever the reason "to do this" might be. I guess that explaining they were forced to cover the reservoir makes me appreciate the solution even more: given an order, they found an intelligent and efficient solution.

Wouldn't it make more sense to add the chlorine after the water is drawn from the reservoir?

Doesn't that fix the bromate problem at the root?

Just a guess, but maybe chlorine needs a good amount of time to be effective, and the transit time from reservoir to tap might not be enough

Why not use ozone to teat the water. It's a better solution that chlorine, even more effective to kill bacteria.

Why not, indeed...

Bromates are formed many different ways in municipal drinking water. The most common is the reaction of ozone and bromide.

Source: https://en.wikipedia.org/wiki/Bromate

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.

Is there any reason why you guys don't have your reservoirs underground? It seems to me that that would solve a lot of problems.

They're pretty hard to dig. Outside resivour can be made by damming a mountain valley and filling it in.

They have space, and they conceived this system, like many others, thinking of what was the easiest thing to do, disregarding a low-maintenance approach.

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