320m3/h Softening Plant

[Eng_Enio1981]

Hello everyone, I am new here and this is my first post.
I am leading a project that will need 320m3/h of softened water.
INLET is fresh water from a river with 540ppm (CaCO3), de-oxygenated and filtered to 1 NTU.

my question is: Considering this important flow rate, Is any other technology apart from exchange ion resin available in the market?

thanks for reading!

 

[PEDARRIN2]

Sounds like municipal flow rates.

Try lime softening

 

[QualityTime]

How soft do you want the water to be and what final pH? Normal lime softening can take the hardness down to about 150 mg/l as CaCO3.

Magnesium lime softening can take it down to about 75-100 mg/L CaCO3. You are adding about 1/3 more lime to get this level of hardness. What you are doing is raising the pH even more to drop out the mangnesium hardness

Then you have to drop the pH of the water down to about 8.5 in order to stop the hardness precipitation and so it is drinkable.

 

[ashtree]

If you did a lot more pre-treatment you could use a nanofiltration membrane in a RO style plant. You would probably require UF as pretreatment or risk a lot of membrane fouling.

Another alternative would be EDR (Electro Dialysis Reversal). EDR would probably handle 1 ntu without much extra pretreatment. This technology is getting pretty rare in the market.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Eng_Enio1981]

good morning,
thanks for your answers, they were very useful.

sorry but I forgot to mention, design outlet quality is 10ppm as CaCO3, and PH increase is not desirable.

I will analyze the alternatives you have mentioned:
1 - lime softening (seems a good way to treat effluent from EDR or nanofiltration)
2- nanofiltration + new pretreatment (ultra filtration unit).
3- EDR (Electro Dialysis Reversal) relaxing new pretreatment

 

[PEDARRIN2]

You are likely not going to get to 10 ppm as CaCO3 with lime softening. Typical effluents I have seen are in the range of 7 grains per gallon or ~120 ppm.

Also, you would likely use the nanofiltration or EDR downstream of the lime softening, not the other way around.

 

[Eng_Enio1981]

@PEDARRIN2, may be for another thread, but my intention is to reuse the water from the concentrated effluent flow for another process. The removal of Ca/Mg is only to avoid future scaling problems.
may be I am wrong but seems easier to precipitate in a concentrated solution therefore consuming less CaOH per day.

 

[ashtree]

Without knowing all the source water quality its pretty hard to say but i doubt that you will get 10mg/l of CaCO3 from any of these technologies without difficulty. Lime softening then NF or EDR might but i would suggest that you might have to go to a tighter membrane process such as RO.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[QualityTime]

I would agree with Ashtree

 

[Eng_Enio1981]

Thanks a lot for your thoughts.
hoping come back later with the outcome.

 

[bimr]

Since this water is from a river, you will need a clarifier and filtration process anyway. It is a simple process to enhance the clarifier with the lime softening process. The effluent quality from the lime softening process will depend on the particulars of the water analysis.

You should be able to achieve the effluent quality of 10 mg/L as CaCO3 from a lime softening, filtration, water softening (ion exchange) scheme. This is a common practice in refineries.

Regarding: "@PEDARRIN2, may be for another thread, but my intention is to reuse the water from the concentrated effluent flow for another process. The removal of Ca/Mg is only to avoid future scaling problems. may be I am wrong but seems easier to precipitate in a concentrated solution therefore consuming less CaOH per day."

The only process that will remove some of the dissolved salts from solution is lime softening. The other processes that were mentioned only concentrate the removed salts into a smaller reject stream.

It may not be easier to precipitate from a concentrated solution. To do this would require additional chemicals beyond the stoichiometric quantity.

If you are interested in recycling the salt concentrated reject stream, you will looking into an evaporator process.