Sterilization Efficiency of Hypochlorous Acid is 50 to 80 times of Sodium hypochlorite (theoretical value)

Hypochlorous acid (HClO) is a strong sterilant and stable, while hypochlorite ion (OCl-) has a low sterilization effect and is unstable. Comparing the sterilization power of these two, the bactericidal power of HClO can reach as much as 80 times that of OCl-. (Please refer to the graph following)

Sterilization Efficiency Measurement

Ex. the E. Coli killing time while chlorine is 0.1mg/L

HClO about 1.5 minute (80 times)/td>
OCl- abuot 120 minute (considered as 1 time)
From the graph left, when the chlorine concentration is 0.1ppm, hypochlorous acid kills 99% of the E. Coli in only 1.5 minute, while hypochlorite ion needs 120 minutes.

Source: Techlonogy of Purifiying Water

The time (in minute) for killing 99% of E. Coli E. Coli (minute) at water temperature 2~6℃

 

The table below shows the relations among that sodium hypochlorite. its pH value, and the consistence rate of HClO

Consistence rate of hypochlorous acid in sodium hypochlorite
Concentration of Sodium hypochlorite pH value of sodium hypochlorite Consistence rate of Hypochlorous Acid (HOCL)
100ppm of Sodium hypochlorite 8.6 6% of HOCl
4,000ppm of Sodium hypochlorite 10.2 0~0.6% of HOCl
120,000ppm of Sodium hypochlorite 11.83 0~0.2% of HOCl

=> while sodium hypochlorite at 4,000ppm (calculate at the optimum level) contains 24ppm of hypochlorous acid (HClO) and 3,976ppm of hypochlorite ion (OCl-)

Assuming the sterilization ability of 1ppm of HClO is one point,
while sodium hypochlorite at 4,000ppm, it consists of
{ 24ppm of HClO → points
3976ppm OCl- → 3976/80=49.7 points

=> Total sterilization point is 73.7 points

As the hypochlorous acid water consists of 100% HClO, when the hypochlorous acid reaches 80ppm, its sterilization points reaches 80 points.

substance sterilization point
SuperAqua 80ppm 80 points
Sodium Hypochlorite 4,000ppm 73.7 points

From the table above, the sterilization efficiency of 4,000ppm sodium hypochlorite is approximate to 80ppm hypochlorous acid.

※ Reference:Tanbo Norihito & Ogasawara Yuichi. Water Purification Technology. Gihodo Shuppan 1985

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