RO ِDI questions

[Benyamin_Givi]

hey guys im just setting up an RO DI system and i have many qustions help pllzzz i have no idea about it

1. is there any membrane to give me 0 tds or its just a wrong idea ?
2. what is DI part in RO DI system is it just mixed resin in a cartridge?
3. what is the best way to have 0 tds? mixed resin?
4. if tds meter shows 0 tds should i test for nitrate or other things ?
5. when i have 0 tds i think every thing is 0. is it true?
6. a guy just told me API test can testing fresh water and saltwater and i can test my RO water with API. is it true?

 

[Randy Holmes-Farley]

No, there is no membrane that can produce 0 TDS water, unless the water coming in has very little TDS to begin with. The DI will take the TDS down to 0 ppm.

The DI can be be mixed bed, or separate anion and cation DI resins. Mixed bed is most common, but doesn't allow DIY recharging which separate beds will. Both ways will produce 0 ppm TDS water.

There is no need to test 0 ppm TDS water for anything. Not everything will be absolutely 0, but there won't be enough of anything to be important.

Which API test are you asking about?

This has more:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

 

[Benyamin_Givi]

thank you randy . i ment the test for nitrate so it seems i dont need it.
thank again

 

[s.h.moradi]

No, there is no membrane that can produce 0 TDS water, unless the water coming in has very little TDS to begin with. The DI will take the TDS down to 0 ppm.

The DI can be be mixed bed, or separate anion and cation DI resins. Mixed bed is most common, but doesn't allow DIY recharging which separate beds will. Both ways will produce 0 ppm TDS water.

There is no need to test 0 ppm TDS water for anything. Not everything will be absolutely 0, but there won't be enough of anything to be important.

Which API test are you asking about?

This has more:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Hi Randy
I got a question and thank you in advance to help me out
the TDS of my RO filter is about 30 and the nitrate is 25 ml/l !!!!
1- is it possible to bring down the nitrate level to near zero just by using DI mixed bed resin?
2- is it absorbing nitrate?!!
2- how should I use the resin? should I connect it to the out let of the filter ?
thanks again

 

[Randy Holmes-Farley]

thank you randy . i ment the test for nitrate so it seems i dont need it.
thank again

You're welcome, and no, you don't need to test it for nitrate.

 

[Randy Holmes-Farley]

Hi Randy
I got a question and thank you in advance to help me out
the TDS of my RO filter is about 30 and the nitrate is 25 ml/l !!!!
1- is it possible to bring down the nitrate level to near zero just by using DI mixed bed resin?
2- is it absorbing nitrate?!!
2- how should I use the resin? should I connect it to the out let of the filter ?
thanks again

I'd be surprised if nitrate is really that high after the RO. It would have to be so high in the source water that it wouldn't be drinkable. In the US, the EPA limits nitrate in drinking water to 10 ppm, and an RO should drop that 10 ppm max to less than 1 ppm.

Regardless, a DI unit of any sort hooked up after the RO membrane will remove the nitrate down to a level where it isn't any concern. Just connect the outlet to the inlet of a DI filter.

 

[s.h.moradi]

I'd be surprised if nitrate is really that high after the RO. It would have to be so high in the source water that it wouldn't be drinkable. In the US, the EPA limits nitrate in drinking water to 10 ppm, and an RO should drop that 10 ppm max to less than 1 ppm.

Regardless, a DI unit of any sort hooked up after the RO membrane will remove the nitrate down to a level where it isn't any concern. Just connect the outlet to the inlet of a DI filter.

thank you Randy for your fast reply and your patience to my boring questions:
if the DI resin has such an ability to bring 25 mg/l nitrate to near zero and the tap water nitrate was 60 then by installing two unit to our tap water there will be no nitrate and no need to RO filter, is it right? or we just have to install the DI unit after the RO filter ?
Im going to buy and install the DI unit and I will test the nitrate level before and after the unit. Which test kit brand, do you recommend to buy to test the purified water?
thanks again

 

[Randy Holmes-Farley]

Nitrate is not normally the most important reason to filter tap water. Copper is a much bigger concern, IMO.

Without the RO, the DI resin will deplete more than 10 times faster.

Install the DI after the RO.

 

[Randy Holmes-Farley]

Nitrate kits are often inaccurate , and I don't have a specific kit I recommend.

 

[s.h.moradi]

Nitrate kits are often inaccurate , and I don't have a specific kit I recommend.

then how do you test your aquarium for nitrate ?

 

[Randy Holmes-Farley]

I personally don't. I know most people do, and it may be useful for them, but I gauge my husbandry practices on the appearance of the aquarium, such as algae growth on the glass, etc.