Saturated pH calculation 1

[vij36]

Dear members,

I am just trying to understand water chemistry.
Excuse me if my queries are too simple.

I am trying to calculate water saturation pH (CaCo3).
We have different water sources approx. daily 15 tankers filling up the sump per day.
Have individual test reports for all these 15 tankers.

Can i average out all these 15 no. pH, TDS, Ca as CaCo3, and total Alkalinity and take the final average value for the purpose of LSI calculation ?

Also for Calcium as CaCo3 did the below:

Calcium hardness as CaCO3/equivalent weight of CaCO3 = = Calcium (mg/L) / equivalent weight of calcium
= Calcium content in water * 50.045 / 20.04

Thanks,

 

[vij36]

Respected members,

Small update to this query. I made a composite sample of all the individual tankers and took the test parameters.

Now my questions are:

1) There are two ways LSI index calculated. One considering total alkalinity and the second is considering total hardness as HCO3. Which method we should consider?
2) I am getting LSI index of 0.51 from first method and 1.1 from second method.

Now to reduce hardness to optimal level and simultaneously to avoid corrosion what is the best approach available.
I heard partial softening and then blend with un-softened water, this will bring down scaling.

Requesting more inputs from honorable members

 

[ashtree]

When you say total hardness as HCO3 do you mean total hardness as CaCO3?
What values are hardness , alkalinity, solution , pH and temperature?

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

 

[vij36]

Dear ashtree,

Total hardness as CaCO3 = 470 mg/ L
So total hardness as HCO3 = total hardness as CaCO3 * 1.22 = 573.4

Total hardness as CaCO3 = 470 mg / L
Total alkalinity as CaCO3= 265 mg / L
pH = 7.5
Temperature = 27 degrees centigrade

I didn't get What is "solution"

 

[vij36]

test report attached

 

[vij36]

Dear members,
I have calculated LSI as 1.1 and RSI as 5.2.
Link
report attached.
Our water consumption is 350,000 liters/ day.
How to calculate how much partial water softening i can opt for ?

Thanks,

 

[vij36]

Respected members,

any info please ...

I have a confusion that what to be considering for calculating LSI.

In LSI formula of LSI = 9.3 + A + B -(C+D) total alkalinity is taken. Source: Link LSI arrived at 0.51
And in another method LSI from the Link HCO3 is considered. LSI arrived at 1.1

I would like to know the difference in both of these methods. Am i wrong in understanding the difference between HCO3 and CaCO3 hardness. From a source it states that HCO3 hardness = 1.22* CaCO3 hardness. Source: Link

Kindly throw some light on this ..

So based on LSI (0.51 or 1.1) how to size the Water softener, meaning how much water need to bypassed around the softener. Total water is around 350,000 liters consumption daily with flow of around 12.5 M3/ hr. Are there any sizing guidelines are available based on LSI index or RSI.

Thanks,

 

[bimr]

The LSI measurement is an estimate. Add up all of the water parameters and then calculate the average parameter.

You will want the LSI to be slightly positive which means slightly scaling as opposed to being negative and corrosive.

Once you determine the LSI that you desire, the percentage of softening required is the LSI hardness divided by the raw water hardness.

The water softener will provide an effluent hardness of 1-5 mg/L. If your desired hardness is 350 and the raw water hardness is 470, the you need to soften (350/470)% of the raw water.

 

[vij36]

Dear Sir,

Thank you very much for the reply.

I have followed your instruction and arrived at below conclusion. Kindly verify.

For Ca hardness ( as CaCO3 ) 325 LSI is 0.47
For Ca hardness (as CaCO3 ) 150 LSI is 0.13

Since 0.13 is close to zero, I assume this is the desired hardness.

So for this hardness the percentage of softening required is approx. 46 %.

 

[bimr]

Looks good to me.

 

[vij36]

Respected members,

After long time I got the approval from our management to install a water softener (they told me to search for a salt free system, which could not be possible which i found from member's inputs here).

Just to recap the above threads info:

Daily consumption: 3,00,000 liters
Total hardness: 470 mg/L
Calcium as Ca: 130 mg/L
TDS: 850 mg/L
Total Alkalinity as CaCO3: 265 mg/L

After LSI calculations it is found that about 50% of softening is optimum. So i have taken quotes for 1,50,000 liters of softening system.
However vendor says the hardness will be reduced by 90%. So will the output hardness (since 90% reduces, Hardness is 50 mg/L) which corresponds to Calcium hardness as 30 mg/L. Will this cause corrosion ? The LSI comes about -0.02. The LSI chart says LSI = 0 means
"Balanced but pitting corrosion possible"

The Softener spec attached.

Requesting kind inputs.

 

[bimr]

Remember that the LSI is an estimate.

To reduce the tendency to be corrosive, you can decrease the percentage of softened water or increase the pH of the water slightly.

What is the end use of the water?

 

[vij36]

Dear Sir,

The end use of water is for bath, cloth wash, cleaning of floors etc., Only concern is the plumbing fittings (however they are of fine grade SS). Got a question that will the bath fittings corrode? So as per your advice will ask plumber to check how to adjust quantity of flow to Softener. I do not know which is the best method, flow regulation to Softener or pH increase. And which is the simpler from maintenance perspective.

I have two more sub queries.

FIRST Query is: Vendor has concern with Softener location because of our location of sand carbon filters.

Our set up has 2 combinations of Sand and carbon filter at the ground
1. Sand filter 4 meter dia. x 2.6 meter height. Carbon filter same dimension (old setup)
2. Sand filter 4 meter dia. x 2 meter height. Carbon filter same dimension (added to first setup)

Then the water is pumped to overhead tank. (10 meter head). I have proposed Softener location at ground after these filters due to space availability and maintenance ease.

The Softener proposal spec: Can handle max 15,000 liters/ hour with max working pressure as 3.5 Kg/Cm2.
The vendor says since the softener which is at ground experiences gravity back pressure from the Overhead tank, his filter may break and resin may leak out.

So now I need to look out for a better location for Softener. He is not able to tell How much minimum back pressure the Softener can handle. He says keep in some terrace but not on the ground.

My SECOND query is: Proposal has one number of 1250 liters resin tank. I have asked him to propose 2 numbers of 600 Liters resin for better results. The cost may increase little. Will this make sense. He also agreed this will have benefit.

Regards,

 

[bimr]

If the fittings are SS, you should not experience any corrosion problems.

Adjust pH will be more of a headache for the maintenance staff and is not recommended.

You would want the water treatment on the bottom floor in case there ever is a leak. The water softener should have a pressure tank rated 50% higher than the maximum water pressure. If the Vendor's equipment can't handle 10 meters of water head, you should look for another supplier.