V. Baratharaj
November 11, 2016

Pharmaceutical product water treatment has been adopting classical disinfection technologies such as chlorine and UV for years together. Each of this technology has its advantages and disadvantages. Ozone technology has been present for more than decades now. With greater awareness and more user experience, ozone technology is close to becoming a priority in pharma water treatment.

Attributes Chlorine Ozone Remarks
Oxidation Potential 1.36 Volts 2.07 volts Ozone more reactive than chlorine 
Disinfection: Bacteria Moderate Excellent  
Disinfection: Virus Moderate Excellent  
Environmental Friendly No. forms by products Friendly Ozone forms, no compounds
Color removal Good Excellent Far reactive than chlorine
Odor removal Fair Excellent Far reactive than chlorine
Carcinogen Formation Very likely Unlikely Safer than chlorine
Bromate Formation No Yes, if not careful Needs precaution
Organics Oxidation Moderate Excellent Far reactive than chlorine
Micro Flocculation Nil Excellent Advantage in ETP
pH Effect Yes. Acidic pH Required No. of action not dependant on pH Advantage Ozone
Water Half Life 2-3 hours 20 minutes Advantage Chlorine
Operation Hazards:
Skin Toxicity &
Inhalation Toxicity
Yes No skin toxicity, Inhalation toxicity - Yes  
Action on Organism Bacteriostatic in most cases Bactericidal Advantage ozone
Mode of action Cell wall lysis Nucleus Lysis on DNA No recurrence with ozone, no re-growth
Action on Bio fouling Fair Excellent Advantage ozone
Specific action on Gram negative and boiler tolerant gram negative (BTGN) Not very good. Requires high dose and long contact time. Bacterial resistance observed. Excellent against Gram Negative bacteria and boiler tolerant bacteria Advantage of ozone in product water
Measurement on line and dependence on water report Not possible to relate on line measurement with bacteriological count Possible, accurate and totally dependable Advantage of ozone
Cost Economical Capital costs Advantage chlorine
Operation Ease Easy to operate Needs careful operation Advantage chlorine

UV V/S Ozone

Pathogens of concern in product water treatment system consist of:

  • Bacteria especially gram negative strains
  • Virus


UV is most effective against bacteria followed by protozoan and least effective against virus.

The normal UV dosage suggested for water treatment is between 20 and 40 mJ/cm2. At this dose, most bacteria show a 2-4 log inactivation.

Disadvantage of UV: Potential for Reactivation

Because UV irradiation does not immediately result in cell lysis, there is some opportunity for a UV inactivated cell to regain viability through repair mechanism. One such mechanism is called photo-reactivation. Following UV inactivation, exposure to wavelengths in the range of 350-450 nm (present in sunlight) triggers an enzyme that can repair UV inflicted damage to the DNA of the bacteria Not all bacteria have this ability to reactivate and it has been found that reactivation decreases with increase in dose from 20 mJ/cm2 - 140 mJ/cm2. As most UV generators are designed at the lower range, the potential for reactivation is a reality!


Viruses are extremely resistant to UV irradiation. California 22 standards require a minimum of 140 mJ/cm2 dose for inactivation of polio virus, while Rota virus needs a minimum of 50 mJ/cm2 dose for effective inactivation and adenovirus needs a minimum of 120 mJ/cm2 dosages. This is clearly lower than the dose recommended by most UV manufacturers.

V. Baratharaj V. Baratharaj is Head, Ozone Technologies & Systems India Pvt Ltd. He can be reached at otsilozone@gmail.com, and +91 44 4211 8266.

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