[goodgnus]

In researching how to remove calcium hardness from pool water I've found a company that uses some sort of lime softening method with a flocculant to precipitate calcium carbonate out of pool water and then filtering it out. I'm at 2500ppm hardness which is extremely high. Given the cost of their service I'd like to try this myself and simply vacuum out the precipitated calcium carbonate/minerals. In their videos they pull a sample directly from a pool, add a few ounces of their concoction and give it a swirl, within 15 seconds the calcium is precipitating out and sinking to the bottom of the large cylinder.

Can someone help me decipher the text below?

Thanks!

a lime softening technique generally comprises utilization of a lime , sodium carbonate (also known as soda ash) , a polymer , and carbon dioxide. A base may optionally added in bodies of water where water hardness concentrations may be about 2000 ppm or greater. The base  may comprise any suitable composition with the ability to accept protons, thereby increasing the pH of a solution upon addition to above about 9.6 and potentially to above approximately 11. A base may comprise sodium hydroxide. A base may be added in conjunction with lime Ca(OH) 2 and sodium carbonate.

500 ml sample may be utilized for this determination with 0.4 g lime added. Thereafter, 0.6 g of sodium carbonate may be added to the sample and subsequently mixed with 1 ml of liquid polymer. The contents of the sample may then be left to coagulate. Once this occurs, a sample from the top of the mixture may be taken to determine if the hardness falls below 100 ppm, and if so, the ratios of the lime, sodium carbonate and polymer are scaled up by appropriate stoichiometric ratios for the entire enclosed body of water.

A lime softening technique may be applied to a swimming pool comprising representative initial readings of: magnesium=32 mg/L as Mg; total hardness=345 mg/L as CaCO 3 ; bicarbonate alkalinity=156 mg/L as HCO 3 —; total alkalinity=128 mg/L as CaCO 3 ; and carbon dioxide=5 mg/L as CO 2 . In order to substantially maximize the effectiveness of the lime softening, a calculation of lime  and sodium carbonate dosage should be performed. In order to determine this, all concentrations of initial readings may be converted to equivalent CaCO 3 concentrations. This determination may be performed using equivalent weights as follows: Ca=20; Mg=12; HCO 3 —=61; CO 2 =22; and CaCO 3 =50. Now, expressing all concentrations as CaCO 3 concentrations, we have:

magnesium (32 mg/L) (50/12)=133.33 mg/L as CaCO 3 ;

total hardness (no conversion needed)=345 mg/L as CaCO 3 ;

Bicarbonate alkalinity (156 mg/L)(50/61)=127.87 mg/Las CaCO 3 ;

Total alkalinity (no conversion needed)=128 mg/L as CaCO 3 ; and

Carbon dioxide (5 mg/L)(50/22)=11.36 mg/L as CaCO 3 ;

Lime dosage may be determined using the following equation:

Lime dosage=[CO2]+[HCO 3 —]+[Mg]+[excess desired]

In this representative case, the lime dosage needed corresponds to about 11.36 mg/L+128 mg/L+133.33 mg/L+0=(272.69 mg/L as CaCO 3 ) (28/50)=95.12 mg/L as CaO.

Sodium Carbonate dosage may be determined using the following equation:
Sodium Carbonate dosage=[total hardness]−[HCO 3 —]+[excess]=345 mg/L−128 mg/L+0=(217 mg/L as CaCO 3 )(28/50)=29.54 mg/L as Na 2 CO 3 .

[goodgnus]

Whoops, that last part got cut off. Also, I just realized this is Forums for Students. Let me know if this needs to be asked in a different subforum.

Sodium Carbonate 115  dosage may be determined using the following equation:
Sodium Carbonate dosage=[total hardness]−[HCO 3 —]+[excess]=345 mg/L−128 mg/L+0=(217 mg/L as CaCO 3 )(28/50)=29.54 mg/L as Na 2 CO 3

Thanks

-Tom

[goodgnus]

Sodium Carbonate dosage may be determined using the following equation:
Sodium Carbonate dosage=[total hardness]-[HCO 3 -]+[excess]=345 mg/L-128 mg/L+0=(217 mg/L as CaCO 3 )(28/50)=29.54 mg/L as Na 2 CO 3