Start here: Disinfection Using Chlorine

It depends upon the dissolved solids in the feed water as to where the pH will go. pH is not so much an issue as the chlorine levels, which are there to provide bacterial resilience.

The chlorination level required will depend upon the length of the distribution system that the chlorine is there to protect. 0.3-0.5ppm is about usual for a drinking water distribution works. 2ppm is about right for a swimming pool - and the water will become unpalatable as a result.

"I want to know how much pH would increase after dosing"

That will depend on how much you dose in .

"What value is good for effective disinfection"

0.5 - 1ppm of free chlorine for drinking water. For other purposes, depends on requirements .

"now also if we want to chec the free chlorine in water, is there any pH correction meter to control the pH."

Yes .

Thanx v much for your valuable suggestions!

Pls tell me if i am dosing 2ppm of sodium hypochlorite then wht wud be pH increase?

can u name any one of such meters(pH correction meter); would CO2 (carbon dioxide) do the job?

for such a strong base, we can assume complete dissociation

if 2ppm is by wt (mg/L) and the final concentration after dosing, then I THINK (not very confident w/ my chemistry - always done something stupid)

pH=-log10((2/0.074442)/(10^6)) = 4.571

Sorry, this is incorrect. Sodium hypochlorite is basic, so the pH will be >7. By knowing the dissociation constant, you can calculate the pH, assuming that the sodium hypochlorite and the water are both very pure. However, this is a very bad assumption in the real world (and I'm too lazy this morning to do the math).

Sodium hypochlorite is likely to contain some sodium hydroxide from the manufacturing process, and drinking water is sure to have some minerals and absorbed CO2.

It is best to measure the pH, rather than trying to calculate.

Tad

"Pls tell me if i am dosing 2ppm of sodium hypochlorite then wht wud be pH increase?"

Honestly speaking, I don't know . That would depend on the original pH level of the water .

"Can u name any one of such meters(pH correction meter)"

ProMinent .

"would CO₂ (carbon dioxide) do the job?"

Do the job of what ? Lowering pH ? Yes .

Hey Megha, sodium hypochlorite is less effective at high pH because the prevalent form is hypochlorite ion instead of hypochlorous acid.

I guess you are disinfecting drinking water. To correct the pH you can use HCl and a pH probe.

Check on www.prominent.com they offer metering pumps and controllers and should have some example online.

I refer you to an article in the Journal of Endodonitcs (April 2008, volume 34, page 449). Clorox is pH 12 out of the bottle. Lowering the pH results in a more effective bacteria killing solution that is also more effective in dissolving tissue, due to the hypochlorous acid form. Of course these actions are also concentration dependent.