RO brew water/starting pH in water

[bretts545]

I work in a water treatment plant and we happen to use an RO system in treating our water.

I want to use this for brewing since where I live the water is not softened and is actually very hard.

I tested the "permeate" from our RO/Membrane softening plant and right now the Total "permanant" hardness is 114 mg/L. This will drop to almost nothing when we change our membranes in a couple months.

I tested the alkalinity and it is low, at 36.

The pH is 5.3.

Now, i know that pH is where i want my mash to end up basically but with low alkalinity and a starting pH around 5.3-5.5 won't my mash drop that pH greatly? low alkalinity subjects that water to drastic changes and I'm just wondering if i should do a blend so my wort pH is not extremely low.

Thanks for any help.

 

[mabrungard]

That is the hardness of the permeate water? That is not very good performance from the RO system, if it is. You mention membrane softening, so this is probably using nanofiltration membranes and not RO membranes. In addition, I expect that they are blending the permeate with some raw water at the end of the process if they don't need really low TDS water.

The 36 ppm alkalinity seems reasonable for the amount of hardness in the water. Clearly, there would be significant permanent hardness in this case since alkalinity is typically equal to the temporary hardness value.

The water pH is not surprising. Dissolved CO2 in the raw water will make it through the membranes into the permeate and that means that the pH will be driven down. The typical approach is to aerate the finished water through an air stripping tower or cascade aerator to drive off some of that CO2, but I don't know what your plant is like. Don't worry too much about the pH value, since there is some alkalinity in the finished water. That will control the mash pH more than the water pH will.

 

[bretts545]

Yeah we have a de-gasifier that the permeate goes through before being blended in the clear well with raw water that is filtered through sand.

The hardness is there because our membranes need changed, we are waiting on GE to manufacture them for us.

What would you recommend I do once our hardness coming out of there is about 30-40 mg/l