does acidity as CaCO3 mean alkalinity as CaCO3?

[dustinstriplin]

I got "Water" by John Palmer and Colin Kaminski for Christmas and am interested in monkeying with my water. The book mentions that alkalinity as CaCO3 is important for calculating residual alkalinity; however, my water report only contains acidity as CaCO3. I'm wondering if these reference the same thing. If not, is there a way to calculate the alkalinity by CaCO3 using the data already provided in the report?

I've attached the 2013 Tacoma WA water analysis.

Thanks for your help, it is much appreciated!

View attachment Tacoma water 2013 analysis.pdf

 

[ajdelange]

Alkalinity and acidity convey the same information i.e. you can calculate one from the other but there is no need here as alkalinity is the second line in the report: 28.0 ppm as CaCO3 for Green River. You calculate RA from this and the calcium and magnesium levels but you must convert them both to CaCO3 or convert them all to mEq/L. That's the easiest IMO. The alkalinity is 28/50 = 0.56 mEq/L, the calcium is 4.56/20 = 0.229 mEq/L and the magnesium 0.82/12.15 mEq/L. The RA, in mEq/L is thus

RA = 28/50 - (4.56/20+0.5*0.82/12.15)/3.5

Convert this to ppm as CaCO3 by multiplying by 50

RA(ppm) = 28 - 50*((4.56/20+0.5*0.82/12.15)/3.5)

Having gone through all that RA really isn't useful for much of anything except comparing one water source to another.

 

[dustinstriplin]

Thanks for the detailed answer! You've helped me a lot!

I guess I was confused because the second line is labeled as "alkalinity". Since I'm new to this, I thought the report needed to explicitly contain an entry for "alkalinity as CaCO3".

 

[ajdelange]

It should be labeled as CaCO3 but we can tell that it is because only if we interpret it that way does the report come close to balancing. Or, simpler than that, as CaCO3 is the only way alkalinity is reported in the USA.