Self purification of limewater

Cory · Feb 3, 2016

Im wondering if 2ppm tds ro water is going to self purify in limewater? Then i wouldnt need to worry about di resin.

Randy Holmes-Farley · Feb 3, 2016

Depends entirely on what it is. 2 ppm TDS is no concern if it is sodium chloride or calcium sulfate. It is a big problem if it is copper cyanide.

That said, settled limewater will help reduce concerns about copper and other toxic metals that might be present.

Cory · Feb 3, 2016

How much will precipitate and settle for the various forms of copper? Lots or little?

How would I suspect?

Randy Holmes-Farley · Feb 4, 2016

In this test (linked below), I showed that limewater with excess calcium hydroxide would precipitate about 87% of a high dose of copper, and adding more calcium hydroxide in a second addition removes more than 97%.

So I'd expect a significant drop if there was significant copper, and would expect that 2 ppm TDS water from an RO/DI is likely fine from a copper perspective when used with limewater. Beware, however,t aht when a DI starts to deplete, things like ammonia (from chloramine) might actually be higher in the effluent than in the source water, and limewater does not reduce ammonia.

Chemistry And The Aquarium: Metals In Limewater ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/issues/may2003/chem.htm

Cory · Feb 4, 2016

Thats was an interesting test. Good to know. Not a good idea to leave my expired deion resin in then? Im curious how chloramine gets to the deion resin. I thought the carbon filter removed that.

Randy Holmes-Farley · Feb 4, 2016

Cory said:
Thats was an interesting test. Good to know. Not a good idea to leave my expired deion resin in then? Im curious how chloramine gets to the deion resin. I thought the carbon filter removed that.

It breaks the chloramine into chloride and ammonia. Both get caught in a DI, but ammonium is one of the weaker binding ions to a typical DI resin, so when the DI begins to be depleted, and sodium or calcium are entering the DI, they can bump off the ammonium.

Cory · Feb 4, 2016

Randy Holmes-Farley said:
It breaks the chloramine into chloride and ammonia. Both get caught in a DI, but ammonium is one of the weaker binding ions to a typical DI resin, so when the DI begins to be depleted, and sodium or calcium are entering the DI, they can bump off the ammonium.

Sounds better to take off my deion resin then, its not worth the risk of having ammonium be released. I wonder if thats why the ro/di tasted bitter once. Fwiw my deion resin didnt work right from the start. It didnt reduce the tds. Strange because my first batch of deion worked great. But i left it there assuming it was doing something.