RODI micron question

[Craigdillman]

Check out aquasafe Canada there to RODI machines are awesome they have quick shipping and solid prices on filters. Got a setup with drinking tap and 4 gallon too off container for round. 185$ ish

[StirCrazy]

Originally Posted by Myka

I was just digging up some links for another thread, and came across Randy Holmes-Farley's comments on what passes through RO membranes:

yup not 100% in another article by him, he does tests and finds he normaly starts out with about 2ppm and the ro brings it down to about .1 - .2

now in a healthy reef aquarium when you test the water you will probably see 0 as your bacteria will reduce it rather quickly.

now having said all that membran selection is obviously important also, as diferent brands and different construction methods give different rejection ratesof different elements, the rejection rate advertised is just for stabalized salt.

I just reviewed some of my documents and amonia is a trickey one, it can either pass through or be rejected depending on the PH and temp of the water which would explain why I always got 0 amonia out of my RO in Victoria and here in kamloops (city is fed by ro system) I will just post the explanation from my Dow lititure.

"
Dissolved gases like ammonia (NH3) will not be rejected by an RO membrane; however, NH3 is in equilibrium with the ammonium cation (NH4+), as defined by the following equation:

NH3 + H+ <---> NH4+
Decreasing the pH and/or temperature will convert NH3 to NH4+, which is rejected by the FILMTEC RO membrane.
For example, as long as the temperature and pH are less than 40°C (104°F) and 7 respectively, more than 95% will be present as NH4+ and the rejection should be better than 98%. However, if both parameters are allowed to increase, the amount of ammonia will also increase, accompanied by a corresponding decrease in rejection by the RO membrane. "

so the hardness of your water does make a difference in the rejection, which would lead to the question if your RO runs after the water softener would this help in that area? would be neat to see if some one has one if they could do with and with out testing.

Steve

[Myka]

Originally Posted by StirCrazy

the RO membrane its self will reduce ammonia to very low levels, depending on the PH of the water, design of the membrane and such, I supose if you still have residual ammonia you coudl use a DI, or other softener type ion-exchange. but to say the ammonia carries on throught the RO untouched is not right at all.

Steve

I have seen this in my own fish only systems that get RO with no DI filtering. After carbon my tap water usually has about 2 ppm ammonia. After the RO membrane there is still 2 ppm ammonia that I use a detoxifier on. I'm using dual 150 gpd 98% rejection membranes.



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