Ozone has been used consistently in US city to sterilize drinking water in municipal water treatment since the 1940s. The use of ozone for water treatment is one of the oldest and best known ozone applications worldwide.
Until 2013, ozone is used by at least 280 American water treatment plants (WTPs). This includes only the ones with a capacity of 1 MGD or greater. According to calculation, they have achieved a capacity of 14.5 billion gallons per day in which 600,000 lb./day is contributed with the use of ozone. Since 1993, ozone technology has been used by at least 55 of these plants. Being cost effective, ozone has been proved to be a good solution for this application.
Ozone is a more effective disinfectant against bacteria and viruses than chlorination when used in municipal water treatment. Its strong oxidizing property also reduces the concentration of iron, manganese, and sulfur. By doing this, ozone can also reduce or eliminate taste and odor in water. Iron, manganese and sulfur in water can be oxidized by ozone to form insoluble metal oxides or elemental sulfur. Ozone makes the later filtration of these insoluble particles much easier. And by coagulation or chemical oxidation, organic particles and chemicals can also be removed.
How the Ozonation Works
Oxygen can be changed into ozone with the existence of energy. This process is realized by either by an electric discharge field in a corona discharge type ozone generator or by UV light in a UV type ozone generator. Except for these commercial ways, there is also electrolysis and chemical reactions that also produces ozone.
A typical ozonation system generally includes providing dry and clean air through a high voltage electric discharge field which creates an ozone concentration of approximately 10,000 mg/L. When used for the treatment of a small scale of wastes, UV ozonation is commonly used. And for large ozone systems, either corona discharge or other bulk ozone-producing methods will be used.
Then, raw water will go through a venturi throat which creates a vacuum. There, ozone gas will be pulled (dissolved) into water or be bubbled up by bubble stones. Ozone will then react with metals in the water to create insoluble metal oxides, followed by a filtration process.
Key Benefits of Ozone
- Ozone has a stronger bactericidal properties than chlorination, a better pH value adaptability and a shorter reaction time.
- Ozone has a stronger oxidizing power against bacteria, viruses, and protozoans than chlorination.
- No chemicals will be added to the water during its oxidization process.
- Countless inorganic, organic, microbiological problems, as well as taste and odor problems, can be easily solved with the use of ozone.
- Ozone can neutralize microbial agents including bacteria, viruses, protozoa and other waterborne pathogens. They include chlorine-resistant microorganisms such as Giardia, Cryptosporidium which are commonly found in municipal water treatment practices.
To learn more benefits by using an ozone generator, please go to: Major Advantages of Ozone Generator.
The Next Task for Ozone
What is expected in the future municipal water treatment is the removal of micropollutants and endocrine disrupting chemicals (EDCs). Micropollutants are low concentration substances which is difficult or impossible to filter with conventional methods.
Long-term discharge of wastewater into rivers and lakes can lead to a gradual accumulation of EDCs. If these rivers and lakes are used to supply drinking water plants, then this will be an urgent water quality problem that needs attention.
For removing EDCs in municipal water treatment, the use of ozone has been proven to be highly effective. The micro constituents that can be handled by ozone include Androstenedione, Carbamazepine, Diclofenac, Estriol, Ethynylestradiol, Ibuprofen, Progesterone, Testosterone, etc.