TDS puzzle

[gwand]

Because my tap water has a persistent nitrate level of 30 ppm I have been playing around with various rechargeable nitrate binding resins that fit into a HOB filter box. The latest one is Cobalt Total Nitrate. Before the addition of the resin my GH was 212 ppm and TDS 330 ppm. After the resin was in the HOB box for 48 hours the GH was 178 ppm, TDS 130 ppm and nitrate fell from 30 ppm to 5 ppm. How could the TDS fall so precipitously? What anions besides nitrate could the resin be binding in order for the TDS to fall so much.

 

[Back in the fold]

I would VERY interested to know the reasons here . Anybody know ?

 

[anewbie]

Well the drop in the gh suggest that the stuff is absorbing minerals in addition to nitrate. There is a direct relationship between gh,kh and tds.

So perhaps your question should be why did the gh fall.... you could email the producer of that stuff and ask why your gh is falling when you use it.

 

[MaloK]

Looks like the resin interact with other negatively charged ions in the water.

Chloride, Sulfate and Carbonate/Bicarbonate.

 

[gwand]

I agree that it’s the most likely scenario.