I need to lower alkalinity in 800 gal of water...?

Question

My plant has an 800 gallon tank (of 120 degree water) that they need to empty, clean, and refill every 3 weeks. In order to dispose of the water properly, it needs to be ph neutral. I'm trying to come up with the most cost effective way to do this.

The current alkalinity level of the tank is 9, and I need to know exactly how much of what I would need to add to that to bring it down to 7.

I'm currently looking at pool chemicals, but I'm sure there has to be a better way. Thanks in advance for any help!

Answer 1

You may buy 2.5 liters of concentrated hydrochloric acid from Sigma-Aldrich for $33.20 (www.sigma-aldrich.com, catalog #435570). I cannot tell you exactly how much must be used to lower the pH of your water from 9 to 7 because I do not know the buffering capacity of your water's impurities. You will need to add the HCl stepwise (like maybe 500 ml at a time), mix well, and then recheck the pH. If the water is heavily buffered you may need to add a lot more than 2.5 liters, but give it a try. Chances are that you won't need to add all that much.

Good luck.

Answer 2

Just dilute the water. Water is typicaly pH 7 if it isn't "hard water" (meaning no minerals like calcium). Get some distilled water, which by definition is pH 7, remove some old water and replace gallon-for-gallon with distilled water. It will bring the pH down towards 7.