H2SO4 to reduce PH 2

[zouzounia]

Hello,

1) In a surface water treatment plant we use H2SO4 to reduce PH (from 8.5 to 7.4-7.5) before coagulation with alum. Can you suggest any papers/work related with H2SO4 dosing & results for PH reduction (best coagulation).

2)Afterwards, we use Ca(OH)2 to increase PH. I need to know the relation among conductivity/lime saturation/ph in order to calculate the dose.

Thank's

 

[bimr]

Most would not bother adjusting the pH because of the cost. They would instead use a coagulant that would allow flocculation at a higher pH.

To adjust the pH, you need to know the alkalinity of the water.

1 mg/l of 98% Sulfuric Acid will reduce the alkalinity by 1 mg/l.

1 mg/l of hydrated lime will increase the alkalinity by 1.26 mg/l

Check out Water Supply and Pollution Control by Viessman and Hammer for further information.

 

[cub3bead]

The optimum pH for alum coagulation to work is 6.8 - 7.2 after the alum dosing. If pretreating with acid to 7.4 pH allows you to stay within that range after the alum dose then you are on the right track.