■ About Ozone

　

What is ozone?

Ozone is a triatomic form of oxygen and is commonly denoted O3. It is formed naturally in the upper atmosphere (stratosphere 15-30 km height) by photochemical reactions with solar ultraviolet radiation. Ozone absorbs UV radiation (peak at 250 nm) to protect us from the Sun’s harmful rays.

Under ambient condition, ozone is bluish gas of odor. In liquid phase ozone has blue color. In solid phase ozone is dark purple color. Depending on the concentration, the odor ranges from slightly sweet (0.05 ppm <), moderately antiseptic (0.1ppm <) to irritating pungent odor.

　

What is history of ozone?

On March 13, 1839 German scientist Christian Friedrich Schoenbein presented a lecture to the Basle natural Society titled “On the smell at the positive electrode during the electrolysis of water.” This is the moment of birth of Ozone. In the beginning and in lack of better wording he called the new substance “smell oxygen,” an excellent name from today’s perspective. -Taken from Proceedings 200th Anniversary of Christian Friedrich Schoenbein, Christian Friedrich Schoenbein empiricism and speculation by Peter Nolte.

　

What are the characteristics of ozone and oxygen? 

  Molecular formula

O3

O2

  Molecular weight (g/mol.)

47.9982

31.9988

  Melting point (ºK)

80.1

54.4

  Boiling point (ºK)

161.8

90.2

  Critical temperature (ºK)

261.1

154.6

  Critical pressure (Mpa)

5.57

5.043

  Critical density (g/cm3)

0.54

0.436

  Critical compression factor

0.228

0.288

  Standard enthalpy of formation at 298.15 ºK in J/mol

142.7

0.0

  Standard Gibbs energy of formation at 298.15 ºK in J/mol

163.2

--

  Standard entropy 298.15 ºK in J/mol K

238.9

205.2

  Heat capacity at constant pressure at 298.15 ºK J/mol K

39.2

29.4

  Permittivity in Debye

1.0017

 --

  Permanent dipole

0.534

0

The above values are taken from CRC Handbook of Chemistry and Physics.

　

What is threshold limit value for ozone?

Threshold limit value for ozone is 0.1 ppm airborne concentration under which it is believed that nearly all workers may be repeatedly exposed day after day (8 hours workday and 40 hours workweek) without effect. – Taken from CRC Handbook of Chemistry and Physics.

　

What is the oxidizing ability of ozone compared with other oxidation agents?

Oxidation agents

Reduction potential (eV)

  F2 + 2e- => 2F-

3.06

  OH (hydroxyl radical)

2.80

  O (atomic oxygen)

2.42

  O3 + 2H+ + 2e- => O2 +H2O

2.07

  H2O2 + 2H+ + 2e- => 2H2O

1.77

  MnO4 + 8H+ + 5e- => Mn2+ 4H2O

1.49

  Cl2 + 2e- => 2Cl-

1.36

  O2 + 2H2O + 4e- => 4OH-

0.40

　

How long will ozone last?

In water, the concentration of ozone will decay to half within 22 minutes. In a confined area it will decay within an hour. Both decay rates are temperature dependent. The higher the temperature the faster the decay rate.

　

What are the benefits for using ozone?

Ozone has the distinct advantage of no remaining and no limit to the ozone dosage. In recent years, one has witnessed a gradual replacement of chlorine by ozone as a disinfectant and an advanced oxidant.

　

What are the drawbacks for using ozone?

Ozone will decompose within an hour. That is to say, there is no such a bottle of ozone gas ready to be used. Ozone has to be on-site produced. For some applications ozone is not economically feasible.

　

How is ozone produced?

Ozone, practically, is usually produced by UV radiation or high voltage discharge.

　

What can ozone does to the bacteria?

Ozone Inaction of Pseudomonas aeruginosa, Escherichia coli, Shigella sonnei and Salmonella typhimurium in Water

Authors: Lezcano, R. Perez Rey, Ch. Baluja and E. Sanchez

Taken from Ozone Sciences & Engineering Vol. 21, pp. 293-300

The table lists the results of the first order inactivation kinetics with respect to both the concentration of ozone and microorganism (Pseudomonas aeruginosa, Escherichia coli, Shigella sonnei and Salmonella typhimurium). The values of 90% inactivation (t90) obtained varied from 0.20 minutes to 8.33 minutes.

                log N0 = log N-k1t

where

               k1 : first order inactivation rate constant

               N0: initial bacterial concentration (cfu/ml)

　

FIRST ORDER INACTIVATION RATE CONSTANTS VALUE OF t90 

BACTERIAL STRAINS

[O3] mg/l

r

log No ± Σy

k1 (min-1)

t90 (min)

Pseudomonas aeruginosa

ATCC

27853

0.41

0.97*

4.6 ± 0.5

1.48 ± 0.02

0.67

1.11

0.96*

6.2 ± 0.1

2.18 ± 0.06

0.45

1.34

0.86*

3.0 ± 1.0

1.90 ± 0.01

0.52

1.78

0.90*

5.2 ± 0.6

4.63 ± 0.06

0.22

2.61

0.90*

4.9 ± 0.7

4.7 ± 0.1

0.21

Escherichia coli

ATCC

25922

0.39

0.95*

5.9 ± 0.9

1.02 ± 0.06

0.98

0.94

0.99*

4.1 ± 0.2

2.39 ± 0.09

0.41

1.40

0.84*

4.4 ± 0.1

3.0 ± 0.9

0.33

2.3

0.81*

5.1 ± 0.5

4.20 ± 0.04

0.23

2.4

0.92*

5.3 ± 0.6

5.35 ± 0.01

0.20

Salmonella typhimurium

0.48

0.89*

5.1 ± 0.8

0.29 ± 0.02

3.44

0.58

0.89*

5.3 ± 0.9

0.27 ± 0.03

3.59

1.04

0.89*

4.0 ± 0.9

0.59 ± 0.0 

1.69

1.75

0.85*

4.0 ± 0.9

1.61 ± 0.02

0.62

Shigella sonnei

0.50

0.98*

4.1 ± 0.9

0.57 ± 0.05

1.75

0.61

0.78*

4.0 ± 0.9

0.57 ± 0.09

1.75

0.88

0.97*

4.6 ± 0.7

0.74 ± 0.03

1.35

1.87

0.85*

3.7 ± 0.8

1.38 ± 0.06

0.72

2.00

0.83*

3.9 ± 0.6

1.4 ± 0.1

0.70

Escherichia coli

0.50

0.89*

4.0 ± 1.0

0.88 ± 0.05

1.13

0.98

0.93*

4.7 ± 0.9

1.48 ± 0.05

0.67

1.31

0.98*

4.9 ± 0.6

1.64 ± 0.06

0.60

1.80

0.99*

4.2 ± 0.4

2.95 ± 0.05

0.33

Pseudomonas aeruginosa

0.39

0.84*

4.0 ± 0.8

0.12 ± 0.06

8.33

0.60

0.82*

4.0 ± 1.0

0.25 ± 0.04

4.00

0.74

0.95*

5.0 ± 1.0

0.62 ± 0.06

1.61

0.84

0.96*

4.0 ± 1.0

0.97 ± 0.06

1.03

1.34

0.99*

4.9 ± 0.6

0.99 ± 0.07

1.01

2.00

0.97*

3.9 ± 0.6

0.82 ± 0.06

1.21

　

What is cheap and quick way to measure the ozone concentration in water?

Here is the recipe of ozone concentration measured by R7 (Erythrosine) food dye.

Preparation: R7 concentration of 25 ppm

    Step 1: add R7 of 25 mg into water of 100 ml.

    Step 2: take 10 ml solution of step 1, add into water of 90 ml.

    Step 3: store the solution in a dark color bottle or warp with aluminum foil to prevent from being decolorized by light.

Usage:

    Step 1: add certain amount of the solution of step 2 (R7 concentration of 25 ppm) to ozonated water till red color disappear.

    Step 2: determine the ozone concentration from the table.

Volume of R7 ml

Ozone concentration ppm

2.4

0.05

2.7

0.1

3.1

0.15

3.5

0.2

3.8

0.25

4.2

0.3

4.9

0.4

Note: for coarse measurement only