Zinc in RO/DI water

[NY_Caveman]

I received ATI ICP-OES results for my new build and the only real surprise to me was elevated Zinc at 11.47 μg/l. More concerning though was the Zinc level was high in my RO/DI water at 3.78 μg/l.

I am not overly concerned about Zinc in general, but I am concerned it is present in my RO/DI water. I have a BRS 4 Stage RO/DI Value unit that is six months old and has probably made 200 gallons of RO/DI. TDS is always and still 0. Anything in particular I should be looking at as a source of Zinc?

I have attached the two reports if anyone is curious or wants more information. Thanks in advance.

 

[Retro Reefer]

It’s my understanding that zinc can be difficult to remove, having optimum pressure to your membrane will supposedly help remove more zinc as well as using dual membrane systems.. don’t think zinc is that big of concern in your reef but you can use absorption media like poly filters to remove it.

 

[NY_Caveman]

having optimum pressure to your membrane will supposedly help remove more zinc as well as using dual membrane systems.

Interesting. Thanks. I run it around 90 PSI out of the faucet. The “out of the tap” TDS is usually around 35.

 

[Retro Reefer]

Here is a paper on heavy metal removal via RO you might find useful

https://actamont.tuke.sk/pdf/2009/n3/6bakalar.pdf

 

[Retro Reefer]

TDS of 35 from your tap is really low.. you must be in upstate

 

[NY_Caveman]

TDS of 35 from your tap is really low.. you must be in upstate

White Plains, NY. About 30 miles north of Manhattan. It is good water, but the Phosphate level out of the tap is 2 ppm.

Thanks for the paper!

 

[Randy Holmes-Farley Verified Community Expert]

If the water is 0 ppm TDS, I am skeptical that the RO/DI is the source, and I'd look for any metal parts touching the DI water, including pumps, float switches, etc. Some folks have found a rusting wing nut on a float switch.

FWIW, I also do not think that level in the RO/Di is a big concern.It would take 300 days of top off at 1% daily evaporation replacement to add what is present in the tank.

 

[Victoria M]

any chance you have a metal component of some sort in your ro reservoir?

 

[NY_Caveman]

any chance you have a metal component of some sort in your ro reservoir?

Good thought, but I use food grade 5 gallon and 2.5 gallon jugs. Pure plastic. When I change out the RO/DI filters soon I will take the whole unit apart and see if there is anything questionable.

 

[NY_Caveman]

If the water is 0 ppm TDS, I am skeptical that the RO/DI is the source, and I'd look for any metal parts touching the DI water, including pumps, float switches, etc. Some folks have found a rusting wing nut on a float switch.

FWIW, I also do not think that level in the RO/Di is a big concern.It would take 300 days of top off at 1% daily evaporation replacement to add what is present in the tank.

Good point. It is a new system, but even on the fill, the system should not read that much higher than the RO/DI. All new components in the system as well. Guess I need to start checking everything.

 

[Victoria M]

I believe there is not going to be anything in the unit. Do you use an ATO? Have you checked your pumps for wear? was the water sample right from the ro di unit? or from the resevoir? via a pump?

 

[NY_Caveman]

I believe there is not going to be anything in the unit. Do you use an ATO? Have you checked your pumps for wear? was the water sample right from the ro di unit? or from the resevoir? via a pump?

The RO/DI sample was direct from the BRS unit. Everything in the tank is new. Tank has been up since July 1st only. I guess my first guess would be a 3D printed magnetic probe holder I picked up. That is the only thing in there that was not from a well known manufacturer. The other magnets are on the Tunze 9004 Skimmer and the IceCap 1k Gyre. I will take the returns apart too and see how they look.

Thanks everyone.

 

[Victoria M]

magnet! 'cept it does not explain the ro di water. Was it collected right to their vial?

 

[NY_Caveman]

magnet! 'cept it does not explain the ro di water. Was it collected right to their vial?

Yep. So it is either passing through from the tap, in the RO/DI unit (unlikely) or from the plastic jug (also seems unlikely).

 

[Victoria M]

is it possible that the tap water is so high in zinc that the membrane can not clear it all?

 

[NY_Caveman]

Here is the White Plains 2017 report. Zinc was measured at 10.6 µg/l.

http://www.cityofwhiteplains.com/DocumentCenter/View/2885

 

[Randy Holmes-Farley Verified Community Expert]

Here is the White Plains 2017 report. Zinc was measured at 10.6 µg/l.

http://www.cityofwhiteplains.com/DocumentCenter/View/2885

Seems extremely doubtful that the RO/DI effluent is the source, if it is 0 ppm TDS and assuming it is not plumbed with metal fittings anywhere.

 

[Victoria M]

Is this zinc number worrisome?

 

[Randy Holmes-Farley Verified Community Expert]

It is very difficult to give an exact answer on toxic levels of trace metals since it depends heavily on the form present (in this case of zinc, that is mostly whether it is bound by organics, which ones, and to what extent). But IMO, that value is not enough above NSW levels to be a major concern.

 

[Victoria M]

It is very difficult to give an exact answer on toxic levels of trace metals since it depends heavily on the form present (in this case of zinc, that is mostly whether it is bound by organics, which ones, and to what extent). But IMO, that value is not enough above NSW levels to be a major concern.

Thank tou for clarifying that.