Insightful article

Just came across this and it opened my eyes to a few facts. I truly believed that RO/DI water is absolutely pure, and in one sense, it is...however, read this article;
References - Diatoms

 

Wow..always knew that silicates brought on diatoms..but i figured the ro/di system would wipe them out

 

Yes, that is what I was led to believe.

 

so are you saying you can have sillicates in water with 0 TDS?

 

The only problem with Albert's old writing is that over the years, there are a lot of hobbyists using siica sand for substrate, that DON'T have the diatom problem.
RO people have stated that RO removes 90 to 98% of silica in water.
In my case, I use municipal water with low (8ppm) silica levels and do no treatment other than aerate the water for a couple of days to remove chlorine.
In most of my tanks, I don't have a diatom problem. Two of my tanks DO have a problem.
The tanks ALL receive the same treatments, the same salt, same everything other than contents as in fish/inverts/corals.
This would suggest to me, that the 8ppm silica is not the cause of the problem diatoms in my tanks as most of the tanks have the same water and DON'T have diatoms.
In any case, if you have concerns about silica levels after RO, why not get a test kit and check it out?
Some might find this link interesting.
Silica Removal from Water

 

I think the gist of this article is basically: filters, resins, etc. of an RO/DI unit need to be periodically cleaned/replaced or they'll stop filtering to 0 TDS. I think the article is trying to say more than that, but that's all I got out of it.

 

good to know thanks for the info Jed...k+ for you

 

No, I'M not saying anything. It is in the article, again; References - Diatoms

 

Silica is a big problem in power plants. ROs are an effective way to remove them, but not good enough for us. A DI train needs to be used. We monitor silica levels of our RO/DI, they are measured in PPB. We also measure conductivity which is the same way we measure TDS. Silica will break through before conductivity goes up. But not way before, and again we can get our water out of a DI train down to 10 PPB. So RO/DI is very effective at removing silica.

The article says .5 PPM is safe... around the time conductivity starts to climb.... silica will be around 60-75 PPB.... so again, no time to panic that you are getting 50 PPM punching through your RO/DI.

Bottom line is RO/DIs are only as good as your maintenance. You must monitor, and know when they have been exhausted. If you are using a color changing resin in a column.... you will have break through before it is all exhausted. We use a column of resin to produce a reference sample for one of our tests. The column is about 10". Once the line for color change gets to about 2-3 inches left....it's time to change and we can see break though.

Maybe not totally scientific... but maybe that helps a little. I guess what I'm trying to say is don't freak out that RO/DI is worthless. Quite the contrary.

 

Yes! You got the gist of the article......