Wastewater Disinfection Using Ozone to Remove Free-Living, Highly Pathogenic Bacteria and Amoebae (OVERVIEW)
Teresa Orta de Velasquez, Neftali Rojas-Valencia, and Alberto Ayala
National Autonomous University of Mexico
Received: January 7, 2008
Accepted: May 16, 2008
The study was done to determine the effectiveness of ozone as a disinfectant against microorganisms in wastewaters that have developed high resistance to common disinfectants such as chlorine. Ozone was applied to Vibrio cholerae and Salmonella typhi bacteria, Acanthamoeba protozoa, total coliform (TC) and fecal coliform (FC). Results showed that at 14 minutes of ozonation, all bacteria and amoeba were completely destroyed.
Positive Findings from the Study
- “When ozone is applied, the synthetic samples show a clear decrease in the number of V. cholera, S. typhi, TC, FC and amoebae, at every stage of the ozonation process.”
- “It was noted that at 14 minutes of ozone application, 99.98% of bacteria were eliminated, and no free-living amoebae were detected. In addition, the inactivation of microorganisms gives first-order kinetics after the application of ozone.”
- “From previous experience and other research, it is known that ozone can break down cell membranes and protoplasm, and that this process impedes cell reactivation in bacteria, coliform, virus, and protozoa.”
- “Ozone inactivates bacteria by means of oxidation reactions. The cell membrane is the first site under attack; then the ozone attacks glycoproteins, glycolipids, or certain amino acids, and also acts upon the sulfhydril groups of certain enzymes; the effect of ozone on the cell wall begins to become apparent; the bacterial cell begins to break down after being in contact with ozone; the cell membrane is perforated during this process; and finally, the cell disintegrates or suffers cellular lysis.”
- “Ozone works by making the cell membrane permeable, and then aqueous ozone penetrates the cyst, and damages the cytoplasmic membrane. Further penetration affects the cell nucleus, ribosomes and other structural components.”
- “Ozone has been demonstrated as the most effective disinfectant for the inactivation of Cryptosporidum, and this is significant because Cryptosporidium is considered the most resistant of the protozoa, being as much as ten times more resistant than Giardia.”
- “In all cases, the microorganisms were very susceptible to ozonation, and a marked reducation of bacterial concentration was observed.”
- “It can be observed that most of the pathogenic microorganisms survice the application of chlorine, but they are significantly reduced in number, or eliminated altogether, when ozone is added.”
- “Ozone has the greatest germicidal power, followed by chlorine. Ozone is 25 times more effective than hypochloric acid; 2,500 to 3,000 times more potent and swifter than hypochlorite; and 5,000 times better than chloramine.”
- “Ozone thus effectively destroys bacteria and amoeba that are difficult to combat by other means. Of particular significance is that other disinfection methods involve the use of chemicals which are sometimes hazardous to human consumption, and always detrimental to the environment.”
Negative Findings from the Study
- “As with any other oxidizing agent, ozone has limitation when oxidizing organic and inorganic matter, depending on the nature and concentration of the constituents in the wastewater under treatment.” NOTE: The conditions set-forth in the study seek to replicate conditions in nature, but the laboratory tests are under perfect conditions. As the study states, some organic or inorganic material in wastewater might be resistant to oxidation, so the results might be slightly less than the 99.98% effectiveness seen in the controlled environment.
Thoughts and Comments
This study has combined full-scale laboratory tests and analysis with strong bibliographical resources to prove what has been known for more than a century: ozone eliminates bacteria.
To get a complete copy of this report please Click Here and fill out the Info Request form, and a Mountain High Water Representative will send you a copy.