Any ideas for alternative for RO water?

[Hzuiel]

Oh and the power consumption is 580 watts, running for 8 hours a day 5 days a week would cost you in the ballpark of 9-11 dollars a month in electricity and net you 10 gallons of distilled water for changes and topoff.

 

[disc1]

I don't really like the stainless pot. I'd rather have glass but it shouldn't make a huge difference in quality as long as everything after it is glass.
I guess it would work if you had a really small tank and never had any emergency situation where you need water fast.

My only question that wasn't answered in the link is energy consumption. I'd want to know how much electricity cost before I tried to compare to the waste output on a rodi.

 

[Hzuiel]

Scroll back up, i double posted, sorry.

 

[Mxx]

From the article..


So you're still looking at a 2:1 waste water ratio. Although I guess you don't have to fill it from the tap you could use any water source.

Let's think about a gallon per square meter. Let's say we need 4 gallons per day, that's a decent sized tank between top-off and weekly water changes. So we need 4 square meters of solar still, if we achieve the output of the one mentioned. To put that into terms Americans understand, that is about 6'6" by 6'6". And then what do you do one day when you need more water? Say a coral slimes out and you need to do a few rapid water changes.



I don't know, it would depend on the source of the water. I only mention it because there seems to be this idea (especially around RC) that any time you evaporate and condense water that makes it distilled. People try to call the condensate off their airconditioner or dehumidifier the same thing as distilled. That just isn't the case. I only mention it to illustrate the point that if there were something there you're not going to get it out.



Rainwater can have a lot of nasties in it. First of all, every raindrop has at its core a speck of dust. But moreover, rain picks up a ton of dissolved gasses from the air. The CO2 isn't so big of a deal because all it does is drop the pH. But the other constituents of "acid rain" are soemtimes things you don't want in your tank. All the NOx species will become nitrate eventually. The SOx species will become sulfate, maybe not as big of a problem as nitrate but still.

And even this is assuming the rain came from a perfectly clean sky. Our air is rather polluted these days. With all the industry going on, there's a lot of stuff going up into the sky that comes back down with the rain.

The moral of that story is that rainwater isn't nearly as clean as you would like to think it is. Again, simply having evaporated and condensed does not make it distilled water.

Thanks for the detailed responses above.

That seems rather surprising in part, I wouldn't have expected the flushing of a solar still or having the input water reaching saturation to be nearly that much of a problem. I would have thought you could have eventually just scraped out any built-up salt/solids now and then...

In any case, in terms of output for a still, then say we're using a 6 sqm still, which if you're top-off requires 4 gallons a day then you'd have 50% extra each day to store, resulting in 14 gallons of extra water per week.

I certainly had the idea that evaporated and then condensed water is distilled water. I'd questioned that slightly, but never found anything to the contrary.

Have you ever happened to come across any research I could read further on about the quality of rainwater? It'd something which would interest me from an intellectual perspective at least, even if I'm going to myself stick to my RODI unit. I wouldn't have imagined CO2 and Nitrogen gas to be a problem with rainwater. It will reach equilibrium anyway if just sitting in a container.

I'd not so long ago looked into recycling water change water from a softwater freshwater tank through a KATI/ANI DI unit with rechargeable resin. There were some potential issues there, but a number of upsides as well.

 

[disc1]

Not nitrogen gas. NOx means NO, NO2 etc. These are not nitrite and nitrate, even though they have the same chemical formula they don't have the negative charge. They are neutral molecules and they come from everything from car exhaust to pine trees. When you dissolve then in water they react to eventually form nitric acid which from your tanks perspective is nitrate.

There was a paper someone posted on the latest rainwater thread in the reef discussion board. If I get back to my computer later I'll try to find it.

FWIW I have seen it rain straight mud here in Arkansas when the winds get up in west Texas. The dust gets up there to the point that the raindrops leave brown spots.

 

[disc1]

Oops. I can't edit from my phone but that second sentence has an error. NO and NO2 are oxides of nitrogen alright but they don't share formulas with nitrite and nitrate. I originally had something else and didn't pay attention to how I changed it. NO2 has the same empirical formula as NO2- but NO is definitely not nitrate.

Either way, both species will quickly find their way to being nitric acid. It is a real problem. It erodes statues and rots the paint on old cars. That's what you've always heard called acid rain.

 

[MONSTERUP]

what about upgrading witha second membrain to cut the waste in half

 

[kelp47]

Thanks for all of the great suggestions. I have to do some research on some of the things mentioned above before making a final decision... (I got sidetracked lately as I've been gathering quotes--I have to get a tank with a custom overflow because of placement in the house.)

 

[jrpark22000]

sorry, reply in wrong topic.