House Project: Something For Next Time I Have To Engage in Algal Genocide

I mentioned previously my fun with chlorine bleach to kill algae and sterilize. A reader points to this recent item from Microbe magazine. (No, it's not the magazine that the young, hip, urban bacterium reads for lifestyle hints, but a publication of the American Society for Microbiology.)

Bleach is sold as a stable alkaline solution with a pH value of about 11 or 12. At this alkaline pH value, virtually all of the bleach is in the form of the chlorite ion (OCl-). At an acidic pH value of about 6.0 to 6.8, 90% of the bleach is in the form of hypochlorous acid (HOCl). Hypochlorous acid is 80 to 200 times more antimicrobial than the chlorite ion. Thus a simple formula to prepare an effective antimicrobial dilution of bleach is to add 2.0 oz of concentrated bleach to one gallon of tap water, and then add 2.0 oz of 5% distilled white cooking vinegar, also inexpensive and commonly available, to lower the pH of bleach to about 6.0. This will yield about 800 ppm free available chlorine from hypochlorous acid. Use this acidified bleach in well-ventilated areas as there will be a mild odor of chlorine.

Yes indeedy, there will be the smell of chlorine gas, so be very, very careful with it. But it does suggest that next time, instead of using 15 gallons of bleach, I can use a gallon of bleach and a gallon of vinegar to get the same result, with less unpleasantness in the water while it works its way through the system.