Ozone Properties:

Property	Ozone	vs. Oxygen
Molecular Formula:	O3	O2
Molecular Weight:	48	32
Color:	light blue	colorless
Smell:	- clothes after being outside on clothesline - photocopy machines - smell after lightning storms	- odorless
Solubility in Water (@ O-deg C):	0.64	0.049
Density (g/l):	2.144	1.429
Electrochemical Potential, V:	2.07	1.23

 

Typical O3 half-life vs. Temperature
Gaseous Temp (C) half-life * -50 3-months -35 18-days -25 8-days 20 3-days 120 1.5-hours 250 1.5- seconds	Dissolved in Water (pH 7) Temp (C) half-life 15 30-minutes 20 20-minutes 25 15-minutes 30 12-minutes 35 8-minutes
* These values are based on thermal decomposition only.  No wall effects, humidity, organic loading or other catalytic effects are considered.

Ozone Solubility

The solubility of ozone depends on the water temperature and the ozone concentration in the gas phase:  Units in mg/l or ppm.

 

 

Oxidation Reduction Potential
ORP is a term used frequently in the water treatment & food processing industry. ORP stands
for Oxidation-Reduction Potential.  So what is that? The best definition I can give is that “ORP
is a measure of the cleanliness of the water & its ability to break down contaminants”. It has
a range of -2,000 to + 2,000 and units are in “mV” (millivolts). Since ozone is an oxidizer, we
are only concerned with positive ORP levels (above 0 mV).

Ozone owes its excellent bactericidal, viricide, and sporicidal activities to its powerful oxidizing properties.

Ozone has an oxidation reduction potential of +2.07 volts as compared to HOCL
(the active form of Chlorine in aqueous solution) which is +1.49 volts. It is reported to be 3000
times as germicidal as chlorine. It retains this strong oxidizing capability in aqueous solution,
a property crucial for water disinfection and sterilization, as well as in high humidity air
applications.
 view oxidation reduction potential chart

ORP sensors work by measuring the dissolved oxygen. More contaminants in the water result
in less dissolved oxygen because the organics are consuming the oxygen and therefore, the
lower the ORP level. The higher the ORP level, the more ability the water has to destroy foreign

contaminants such as microbes, or carbon based contaminants.

The chart below identifies ORP levels for various applications:

 

ORP Level (mV)	Application
0-150	No practical use
150-250	Aquaculture
250-350	Cooling Towers
400-475	Swimming pools
450-600	Hot Tubs
600	Water Disinfection *
800	Water Sterilization **
*  Disinfection is destruction of specific pathogenic microorganisms **  Sterilization is the destruction of all microbial life

 

How does an ORP meter work?
An ORP meter measures very small voltages generated with a probe placed in ozonated water. The electrode is made of platinum or gold, which reversibly looses its electrons to the oxidizer. A voltage is generated which is compared to a silver (reference) electrode in a silver salt solution, similar to a pH probe. The more oxidizer available, the greater the voltage difference between the solutions.