Which Water Treatment Method - CEDI?

[kforce]

I am looking at a system that will treat 10 gpm of water from a well with the following characteristics:
pH = 7.4
Conductivity = 700 micromhos/cm
TDS = 340 mg/l
Alk = 202 mg/l
Total Hardness = 191 mg/l
Chloride = 20 mg/l
Sulfates = 120 mg/l
Nitrates = 1.3 mg/l
Calcium = 18 mg/l
Sodium = 13.5 mg/l
Potassium = 10.5 mg/l
Magnesium = 10.7 mg/l

The finished water limitations:
Hardness < 9 dH
Chloride < 50 mg/l
Silica < 150 mg/l
Sulfate < 100 mg/l
Conductivity < 7000 mmohms

Will Continuous Electrodeionization work?

 

[bimr]

Continuous electrodeionization is typically used as a polishing process.

For example, most ultrapure water processes would use the reverse osmosis process to remove the bulk of the salts. Then you pass the RO treated water through the continuous electrodeionization unit.

 

[kforce]

Thanks bimr,

With this feedwater, isn't the sodium and chloride content sufficiently low enough?

 

[bimr]

Sure, the sodium and chloride concentrations are low enough for continuous deionization.

In rereading your post, it appears that you do not need to obtain a high quality finished water. You can get away with treatment for only a portion of the 10 gpm flow and then blending in the untreated water for the balance to obtain the 10 gpm product water.

The water quality that you desire can be achieved using either with RO or CDI.

Not sure what type of equipment is on the market for the flow that you desire. The equipment that is available may also influence your equipment decision.

 

[kforce]

Bimr,

Blending sounds like a good option.

By the way, I am looking at this problem from an overall qa/qc point of view of possible treatment options, but I am not entirely familiar with the some of the units. I am familiar with conductivy units as micromhos/cm, but have not heard of mmhoms - have you heard of them? How do they convert to micromhos?

Thanks again for the help.

 

[bimr]

Conductivity units are Siemens per meter [S/m] in SI and micromhos per centimeter [mmho/cm] in U.S. customary units.

http://www.lenntech.com/water-conductivity.htm

 

[shahyar]

1. Your TDS is far below for using RO. Generally when TDS is lower than 800 mg/L, RO is not an economical method.
If you want to use RO, you need to check if Hardness is not troublesome. You can do it with free manufacturers' softwares.
2. Because you do not need ultrapure water and , as bimr said, CDI is polishing unit, you can use a split design: mix some inlet water with product to get you quality.
3. micro ohm/m (or cm)is unit for resistivity, condictivity unit is micro mho/cm or the other name is micro Siemens/cm. So:
1 micro mho/cm = 1 micro Siemens/cm
10 micro ohm. cm (resistivity)= 0.1 micro Siemens/cm (conductivity)