Why deionization?

[shlap]

Is this just to bring the solid PPM down to 0?

I ask because my TDS meter shows 0 ppm from my local water store and it would be handy if I could use their water once in awhile. They're using some beast filters with UV but no DI filters.

Thanks

[skunkmere]

where do you live?

[shlap]

Phoenix why?

[HighlandReefer]

Reverse Osmosis/Deionization Systems to Purify
Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.php


From Randy's article:

"However, at the small end of the spectrum a number of compounds can pass through a reverse osmosis membrane to some extent and are, therefore, of concern to reef aquarists. These include carbon dioxide (CO2), ammonia (NH3), hydrogen sulfide (H2S, especially a concern with well water) and silicic acid (Si(OH)4, which is the uncharged and predominate form of silicate at pH values below 9.5). All of these should be trapped by a functioning DI resin (discussed below), but can still be a concern.

In the case of CO2, for example, there can be a lot of it in certain well waters, and DI resins may become rapidly depleted because the CO2 so readily passes through RO membranes (how to deal with this is discussed later in this article). As another example, ammonia that comes from chloramine in the water can be significant, and is one reason that RO/DI is greatly preferred to RO alone in those situations where chloramine is added to the tap water.

In the case of silicic acid, some types of RO membranes can be better than others at excluding it, even before it gets to the DI resins. For example, a thin-film polyamide membrane might let only 0.3% of the silicic acid pass, while a similar cellulose acetate membrane might let 12.7% of it pass."

[jeff@zina.com]

Highland Reefer said it well, my main reason for the DI is to clean up residual ammonia from chloramines. My TDS after the membrane is already 0.

Though there's no reason not to use the water from your local store just because it doesn't have DI.

Jeff

[bertoni]

Only RO/DI water should read zero TDS. What exactly are they using to treat the water? UV isn't very useful for this purpose, at least not in marine systems.

[shlap]

Only RO/DI water should read zero TDS. What exactly are they using to treat the water? UV isn't very useful for this purpose, at least not in marine systems.

I couldn't tell you to be honest. All that I know is that the TDS meter shows 0 with their water.

It sounds like regardless of the TDS, there could still be other nasties that the DI membrane gets out. Thanks guys.

[jeff@zina.com]

Only RO/DI water should read zero TDS.

Mine often reads zero before the DI unit, rarely more than a few ppm. It may be because I have low TDS in the supply water, usually 160-180 ppm, decent pressure, a 98% rejection rate and the blessings of a passing monk. It is definitely zero after the DI.

Jeff

[shlap]

... and the blessings of a passing monk.

Hahaha. Classic. :lolspin:

[OwenInAZ]

I use the Water n Ice store at 32nd St and Greenway all the time for water. So far so good.

[shlap]

Hey Owen! Cheato and sump sludge are still doing good :-)

[skunkmere]

just a side note on DI. you need a carbon stage to remove the chlorine from the water before it hit the ro and DI. chlorine and chloramine passes through the RO and if it hits the DI it creates a cancer causing Nitrosamine. I dont know what it does to the our tanks but i just read that.

[bertoni]

Most of the RO units sold have a carbon phase before the membrane that will remove chlorine and break down chloramine. What gets past will be consumed by the DI, assuming it's functioning. This article has more:

http://reefkeeping.com/issues/2003-11/rhf/feature/index.php

I'm not sure how a nitrosamine would be formed, if they can be. Did this source specify what kind of nitrosamine allegedly is produced?

[pezjunkie]

I was always under the impression that chlorine needs to be removed before the RO stage, since it will destroy TFC membranes.

[bertoni]

Chlorine will damage the more common type of membranes that we use, which is the TFC type. There's another kind that actually requires it, the CTA membranes.

[Stars85]

maybe there is something wrong with your TDS meter?

[Fishtastic]

As long as the price is good, just use a little tap water conditioner with it...
Remember when making your own water at home, it's usually 2:1 if not 3:1 waste to output ratio... meaning you use 2-3 gallons of water for 1 gallon of pure water.
This definately adds up if you pay your own water bill...

[skunkmere]

it didnt but i got the info from a water treatment training course im taking.

Most of the RO units sold have a carbon phase before the membrane that will remove chlorine and break down chloramine. What gets past will be consumed by the DI, assuming it's functioning. This article has more:

http://reefkeeping.com/issues/2003-11/rhf/feature/index.php

I'm not sure how a nitrosamine would be formed, if they can be. Did this source specify what kind of nitrosamine allegedly is produced?

[OwenInAZ]

Pubmed/Google Scholar are your friends here. :)

Nitrosamines can indeed be formed from chloramine or other secondary amines. As suggested by skunkmere, most of the research is centered around water treatment facilities where DI resins are used as flocculation agents in the treatment process, although nitrosamines are also present in detectable levels in numerous foods. There is a well-understood chemical pathway for the production of nitrosamines, but seeing as how I'm a genetics nerd and not a chemistry geek it makes my head hurt :) -- for a review see Schreiber and Mitch, 2006. It also looks as if there isn't an agreed upon guideline for how much is too much, although it may be out there and I wasn't able to find it.

I suppose my initial response would be, "meh." The volumes we're talking about aren't large enough to worry about for our purposes. We're not talking millions of gallons an hour here -- most peoples' RODI outputs are measured in the tens to hundreds of gallons per day range. Personally, I'd be more worried about the UV light coming off my halides or the damage the chloramine can do to the RO membrane than any possible byproducts.