Ba,Cu removal & salinity for RO 1

[stamopoulos]

dear group,
we are thinking as a water distributor of constructing a brackish water ro plant and we found in the feed water that Ba=2ppm and Cu=2.22 ppm. Shall we need any kind of pre or post treatment?
Also is it true that i can found an approximate value of the salinity of the feed water using only the conductivity and if yes, can anybody tell me if the conductivity is 5,98mS/cm how much would be the salinity?
Really appreciate for your attention
George, Civil Engineer

 

[cub3bead]

George,

Did you check for SO4 also? that much Ba can cause many problems if you have SO4 present.

You need a complete water analysis to work from in ordeer to design a RO. Ca, Mg, Na, K, Ba, Sr, Fe, Mn, Al and Cu as a minimum for the cations. Anions you will need CO3, HCO3, Cl, SO4, PO4, F, and Br. Others are B, SiO2, and pH.

Your reported Cu may cause problems with discharge of the pretreatment wastes.

With that much Ba you will likely have to use na cycle ion exchange to soften the water. This process will catch all of the di and tri valent cations in the process of taking care of the Ba.

For brackish water I use a factor of 0.65 - 0.7 to estimate the TDS from electrical conductivity. While you are getting the periodic chart analyzed, have the lab run a gravimetric TDS test.

Have you tried measuring the SDI of the source water yet?

 

[stamopoulos]

Thank you cub3bead,

do you mean that TDS is aprox 5,98X0,7=4,186ppm or 4186ppm?

lab found a TDS (i think with gravimetric method)= 3,5ppm which i think is wrong for a brackish water, it should be a 1000 times greater say 3500ppm, thats why i try to find it on my own with an approximate formula.

George

 

[cub3bead]

Shame on me, I knew that you were using the European convention of reporting conductivity as milli S rather than micro S that I normally use and ignored it.

At the conductivity you report I would use a factor of 650 ppm/mS to approximate the TDS or 5,98*650=3887 ppm which is in the ballpark of your 3500.

If you have a complete water analysis, you can also do a quick check by summing the concentration of the constituents as ions.

You might want to go to the Dow, Toray, Hydranautics or TriSep webpages and download their design programs. Koch and Osmonics (GE Water) do not have their programs available for download, you must obtain a copy for a representative.

You might want to try and get a copy of PWT's ProDose to aid in selection of antiscalants.

 

[bimr]

Of course, you are going to need pretreatment. The amount of pretreatment needed will vary depending on whether your source is a surface water or a well water.

 

[jmj5152]

I would caution against using multipliers to obtain TDS of saline water. These conductivity relationships are typically developed as CaCO3 equivalents in typical city or tap water. Every ion contributes a different value to the conductivity of the water, and the concentration of specific ions, and their vapor pressures,scaling tendencies, etc. will determine your R/O operating parameters. As suggested above, first step would be to get an inorganic analysis. Programs available at sites mentioned above will help design pretreatment for you.

 

[cub3bead]

I agree. I only use the multiplier as a sanity check of the other data and do not recommend using them for process design or chemical treatment program selection.

 

[stamopoulos]

thanks for your post all
george