Ozone disinfection of water is a water treatment process that uses the oxidative intensity of ozone to remove pollutants. ozone is introduced into the water, which instantly oxidizes and removes pollutants including bacteria, viruses and metals.
The purpose of disinfection of public water supply is to eliminate germs that cause waterborne infections.
Diseases such as typhoid and paratyphoid fevers, cholera, salmonellosis and shigellosis can be prevented by using treatments that significantly lower the overall number of viable microorganisms in the water.
Water disinfection technologies that are commonly used include ozonation, ultraviolet light and chlorination.
One of nature’s most strong oxidizers, ozone, is a naturally occurring gas in the earth’s atmosphere.
Ozone filters the sun’s ultraviolet light and shields the planet from damaging radiation in the upper atmosphere, but it also helps to provide safe drinking water on the ground through ozone water treatment.
Ozone water treatment is adaptable and may be used in commercial and multifamily housing settings.
Ozone water treatment is a water treatment process that uses the oxidative intensity of ozone to remove pollutants. The production of ozone in an ozone generator is the first step in ozone water treatment.
Then ozone is introduced into the water, which instantly oxidizes and removes pollutants including bacteria, viruses and metals.
How is ozone generated?
When oxygen (O2) molecules are split into oxygen atoms by an energy source, they collide with another oxygen molecule to generate the unstable gas ozone (O3), which is used to disinfect water and wastewater.
Most wastewater treatment plants produce ozone by passing a high-voltage alternating current (6 to 20 kilovolts) across a dielectric discharge gap containing an oxygen-bearing gas.
Because ozone is unstable and decomposes to elemental oxygen in a short period, it is produced on-site.
The free radicals’ hydrogen peroxyl (HO2) and hydroxyl (OH) produced when ozone decomposes in water have the high oxidizing ability and play an important part in the disinfection process.
The bacteria are thought to be eliminated due to protoplasmic oxidation, which causes cell wall collapse (cell lysis).
Enhance the performance of the Ozone generator
Pure oxygen can be used to substitute ambient air and increase the proportion of oxygen in the airstream, improving the performance of the Ozone generator.
Ozone may also be produced in the presence of some UV lights, although only in low quantities.
Ozone is difficult to store and transport since it is extremely reactive and has a short half-life. As a result, it must constantly be created on the spot for instant usage.
The sensitivity of the target organisms, the contact period, and the ozone concentration all influence disinfection efficacy.
Why is ozone disinfection used?
When dissolved in water, ozone forms a broad range of biocide that kills all bacteria, viruses, and cysts. Since 1904, ozone water treatment has been used professionally to clean drinking water.
It was chosen because ozone is a known cost-effective disinfectant that enhances the flavor of treated water while reducing undesired disinfection by-products.
Organic material in the membranes of bacteria, viruses and parasites is oxidized by ozone.
This weakens, ruptures and destroys their cells, allowing the toxins to escape.
Ozone also oxidizes iron, manganese and copper, forming solid particles that may be removed from water using mechanical filtration or activated carbon filters.
Ozone water treatment systems may also remove turbidity and undesirable tastes and smells generated by chlorine through oxidation.
Ozone disinfection involves the following mechanisms
• The cell wall is directly oxidized/destroyed, resulting in the flow of cellular components outside the cell.
• Reactions with ozone destruction radical by-products.
• Damage to the nucleic acid’s components (purines and pyrimidines).
• Depolymerization occurs when carbon-nitrogen bonds are broken.
What are the advantages and disadvantages of employing Ozone as a disinfectant for the environment?
Advantages
While commonly thought of as a disinfectant, Ozone has a wide range of applications.
Ozone offers the following advantages due to its wide spectrum of oxidizing capabilities and environmental benefits:
• Reducing chemical use – because ozone gas is created “in situ,” there are no storage or transportation costs.
• No contaminants — oxygen is the sole ‘breakdown’ product.
• Any wastewater may be safely re-injected into rivers and surface drains, conserving energy and money.
• Most CIP (Cleaning in Place) operations have been drastically reduced.
• Wastewater may be reused in other greywater applications, reducing the need for additional water.
• Avoid the usage of toxic halogens like chlorine and chlorine dioxide.
• When it comes to killing viruses and bacteria, ozone exceeds chlorine.
• Except for those protected by particles in the wastewater stream, there is no regrowth of bacteria after ozonation.
• Ozonation raises the effluent’s dissolved oxygen (DO) content.
Increased DO can reduce the requirement for reaeration while simultaneously increasing DO levels in the receiving stream.
Disadvantages
• This chemical must be constantly monitored due to its toxicity.
• There are greater than deadly ozone concentrations within the ozone system, therefore releasing this gas would be extremely harmful. Ozone detectors and other precautions are required.
• The requirement to adhere to building standards and fire requirements while storing liquid, high-purity oxygen.
Although it produces fewer THMs than chlorine-based disinfectants, bromate is created if bromine is present in the water.
This is also quite risky.
• Because ozone has a half-life of 20 minutes in both air and water, there are no residual kill-off germs in the water beyond this period, necessitating the use of another disinfectant.
• It is also the most expensive technology in our evaluation since the systems must be highly automated and dependable, which comes at a price.
• Some viruses, spores, and cysts may not be efficiently inactivated at low doses.
• Ozonation is a more complicated technology than chlorine or UV disinfection, and it needs specialized equipment and effective contacting systems.
• Because ozone is highly reactive and corrosive, corrosion-resistant materials such as stainless steel are required.
• Ozonation is not cost-effective for wastewater with high suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), or total organic carbon (TOC).
The costs of ozone disinfection technologies
The cost of ozone disinfection systems is determined by the manufacturer, the location, the plant’s capacity and the properties of the treated effluent.
In comparison to other disinfection procedures, the cost of ozonation is often considerable.
A correctly designed system’s main and secondary treatment procedures (BOD concentration does not exceed 30 mg/L, and SS content does not exceed 30 mg/L).
Site-specific factors heavily determine costs, hence the figures that follow are averages that may vary from location to location.
Because the concentration of ozone produced by air or oxygen is so low, the transfer efficiency to the liquid phase is an important economic factor. As a result, contact chambers are often quite deep and covered.
The capital and operating and maintenance costs play a big role in the overall cost of an ozone system.
Power consumption, materials, incidental equipment repairs and personnel requirements are all included in the annual running expenses for ozone disinfection.
Another cost factor is that each ozonation system is site-specific, based on the effluent restrictions of the facility.
For particular cost information, chemical suppliers should be contacted.
Reference
[1] What is Ozone Water Treatment and How Does It Work?, 19 March, [online] Available at: https://www.freshwatercom/blogs/blog/what-is-ozone-water-treatment-and-how-does-it-work
[2] Wastewater Technology Fact Sheet Ozone Disinfection, September, [online] Available at: https://www3.epa.gov/npdes/pubs/ozon.pdf
[3] Ozone Water Treatment FAQs, [online] Available at: https://www.socotec.co.uk/media/faqs/faqs-ozone-water-treatment
[4] Ozone Disinfection for Drinking Water Miramar and Alvarado Water Treatment Plants, [online] Available at: https://www.sandiego.gov/sites/default/files/legacy/cip/pdf/ozonepdf
[5] Ozone (trioxygen or O3); advantages and disadvantages in the water industry, 29 March, [online] Available at: https://www.bridgebiotechnology.com/ozone-trioxygen-or-o3-advantages-and-disadvantages/
