I need a chemist

[Amoo]

Ok Randy or whoever else can help here, got a good one for you guys.

Primary Goal: Use less DI Media
Secondary Goal: Maybe have cleaner/better drinking water

Ok guys let's start with this:

As can be seen there's basically nothing in my water but water and silica. This test was taken from the kitchen sink and my RODI system hooks into the washing machine inlet which is all PVC from the well to the washer so I know I can eliminate at minimum the copper.

It's my understanding there are two ways to to raise water pH. I can aerate the water or I can use a whole house Acid Neutralizer. I'm currently considering both options.

Obviously a degas unit for the whole house would be too expensive so if I go the degas route it would have to be done locally at the RODI unit which I can do.

My other option becomes the Acid Neutralizer which uses Calcite and Corosex. Calcite is Calcium Carbonate which would obviously make my Calcium levels go up from .8ppm. Corosex is Magnesium Oxide.

Based on my pH I should be using a 90/10 blend of Calcium Carbonate/Magnesium Oxide.

What I'm trying to figure out and the reason for this thread is, how much strain would be put on my entire filtering system before the DI filter to remove the increased amounts of Calcium and Magneseum. I'm assuming Calcium and Magnesium is taken out of the water prior to the DI stage?

My planned system would look like this:

Sediment Filter > Neutralizer > Sediment Filter > Well Pump > Well Booster Pump (I already have this instelled) > RODI Unit

RODI configuration as follows:

5Micron Sediment> 1 Micron Sediment> 1Micron Carbon > Dual RO Membranes > DI Canister

 

[saltyfilmfolks]

 

[sbash]

Lol, nice, I am filing this one for future use...

 

[Randy Holmes-Farley]

Your water looks to be mostly sodium silicate. Maybe as pure as what I dose. lol

Is your DI depleting rapidly?

Getting rid of the CO2 that is likely in it will reduce DI consumption. I can't be sure how much CO2 is there without
If you choose the whole house neutralizer, it will add a small amount of calcium and magnesium, but the RO/DI will easily take these out. I expect that will reduce the DI consumption, rather than increase it, by having the RO remove more of the CO2/bicarbonate.

Degassing will also reduce the DI consumption. If done perfectly it won't add anything back and will reduce DI consumption the most, but whether it really is more effective all depends on how well you implement degassing.

Which would be mmore effectibe in this specific case

 

[Amoo]

Your water looks to be mostly sodium silicate. Maybe as pure as what I dose. lol

Is your DI depleting rapidly?

Getting rid of the CO2 that is likely in it will reduce DI consumption. I can't be sure how much CO2 is there without
If you choose the whole house neutralizer, it will add a small amount of calcium and magnesium, but the RO/DI will easily take these out. I expect that will reduce the DI consumption, rather than increase it, by having the RO remove more of the CO2/bicarbonate.

Degassing will also reduce the DI consumption. If done perfectly it won't add anything back and will reduce DI consumption the most, but whether it really is more effective all depends on how well you implement degassing.

Which would be mmore effectibe in this specific case

I wish I had that answer Randy. Based on everything I have read and the fact that my total hardness is exactly 5, everything I can find seems to indicate my low pH is due to the need for more Calc/Mag in my water. Mostly Calc, but mag is just a rapid increaser as you know to bring it above 6.0 then the calc levels it off.

I kill a DI cartridge in less than 30 days and that's making ~100gallons of water.

My only concern by adding more minerals to the water would be they're going to get stripped out by the RO membrane anyways, so if they get stripped out by the RO membrane how does that increase my pH or anybody's for that matter by the time it hits the DI resin?

I was considering implementing both solutions honestly and may still yet, I just don't totally understand the relationship between adding the calc and mag just so it can go into the RO and be taken out and if that will lead to a higher pH hitting the DI resin. I would assume no and I will still have to degas, but I don't know if the cabonate does it's cabontating thing and binds blah blah chemistry causing a permant rise in pH that isn't a direct result in the calcium, but more the carbonate that is being added which binds to whatever raises pH.

Hence I need a chemist

 

[Randy Holmes-Farley]

My only concern by adding more minerals to the water would be they're going to get stripped out by the RO membrane anyways, so if they get stripped out by the RO membrane how does that increase my pH or anybody's for that matter by the time it hits the DI resin?

Adding calcium carbonate to low pH water will convert the CO2/carbonic acid into bicarbonate. The bicarbonate is well rejected by the RO membrane (typical 85+% rejection), as is the calcium (typically 90+% rejection)
CaCO3 + H2CO3 --> Ca++ + 2HCO3-

The problem with CO2 itself before reaction is that it is very poorly rejected by an RO membrane, so gets through to deplete the DI.

 

[Amoo]

Adding calcium carbonate to low pH water will convert the CO2/carbonic acid into bicarbonate. The bicarbonate is well rejected by the RO membrane (typical 85+% rejection), as is the calcium (typically 90+% rejection)
CaCO3 + H2CO3 --> Ca++ + 2HCO3-

The problem with CO2 itself before reaction is that it is very poorly rejected by an RO membrane, so gets through to deplete the DI.

Thanks Randy,

EDIT need to rethink my response and reread what you wrote a few times to make sure I'm tracking

 

[Amoo]

Ok so I read this 6 times so if I'm wrong please correct me as I may be having a not blonde/blonde moment.

So essentially by adding the Neutralizer I will convert some (possibly a significant amount) of my carbonic acid into bicarbonate, which would allow my RO Membranes to reject it before it gets to my DI resins, possibly extending the life of my resins.

I have to check the instructions on the mix I'm supposed to use, but I believe it told me I can get the pH up to somewhere between 7-8, which would be a significant difference from the 5.7 I started with.

Secondarily would a second carbon block catch some of this as well? I could always run, 1micron sediment > Carbon > carbon > RO. It was my understanding the Carbon is mainly there for chlorine and a few other minor things that are of not much concern to me.

 

[Randy Holmes-Farley]

Yes, and carbon block won't help.

 

[Amoo]

Yes, and carbon block won't help.