Applications
Potable water treatment
Ozone Technology's Pressureless Ozonation Systems leverage ozone's capabilities as a highly efficient agent in the treatment of potable water.
Advantages of Pressureless Ozonation Systems for potable water treatment
- Oxidation potential even higher than chlorine
A substance's oxidation potential represents its ability to transform chemicals, the process necessary to purify water. With an oxidation potential 12 times higher than chlorine, ozone is highly effective for water purification.
- Faster disinfection times
Ozone works thousands of times faster than chlorine.
- More thorough and efficient mixing during water treatment
Ozone gas is 12.5 times more soluble than oxygen in water, which results in better mixing during water treatment.
- Effective for controlling a wide variety of tastes and colors
Because ozone is highly reactive with many compounds, it can oxidize numerous types of organics and metals — making it an effective means of controlling many different tastes and odors.
- Superior coagulation
Ozone can provide more effective coagulation than chemical coagulates, an important consideration in water treatment applications such as iron/manganese and total organic carbon (TOC) removal.
- Enhanced filtration
Ozone can enhance contaminant fl occulation and subsequent removal through a variety of filters — resulting in longer filter runs, reduced backwash frequency, and higher-quality treatment effluent.
- Safe, non-chemical method for water treatment
Since the discovery that potentially harmful disinfection byproducts (DBPs) can form in surface water treated with chlorine, ozone's potential as a non-chemical method for treating drinking water is even more important than ever. Recently, regulations have been established for substances that cause health problems and are potential carcinogens, including trihalomethanes, haloacetic acids, bromate, and chlorite. The products formed when ozone reacts with organics are oxygen, carbon dioxide, and water.
In addition, the ozone in Ozone Technology's Pressureless Ozonation Systems is created on-site from ambient air, eliminating safety problems and expense associated with purchasing, shipping, handling, and storing chemicals.
- Environmentally friendly
Ozone is safe for the environment. The EPA does not require any record-keeping or reporting of ozone use.
Disinfection
Ozone is the most powerful disinfectant used by public water systems today.
Ozone is a biocide and works in much the same way as chlorine. Ozone disinfects by directly oxidizing and destroying the microorganism's cell wall. Ozone destroys viruses by diffusing through the virus's protein coat into the nucleic acid core, where it damages viral RNA. At higher concentrations, ozone destroys the virus's exterior protein shell so that DNA or RNA structures are affected.
Ozone destroys parasitic cysts that chlorine is incapable of killing, including:
- Cryptosporidium parvum
- Giardia lamblia
- Giardia muris
Much smaller amounts of ozone required
CT values for the inactivation of Giardia cysts (2-log)
CT values for the inactivation of viruses (2-log)
As shown in the following tables and graphs, adequate disinfection is achieved with much smaller amounts of ozone than with other disinfectants. Ozone outperforms chloramines by several orders of magnitude.
Table 1. CT-values for the inactivation of viruses by various disinfectants
| Disinfectant | Units | Inactivation | ||
|---|---|---|---|---|
| 2-log | 3-log | 4-log | ||
| Chlorine1 | mg · min/L | 3 | 4 | 6 |
| Chloramine2 | mg · min/L | 643 | 1,067 | 1,491 |
| Chlorine Dioxide3 | mg · min/L | 4.2 | 12.8 | 25.1 |
| Ozone | mg · min/L | 0.5 | 0.8 | 1.0 |
| UV | mW · s/cm2 | 21 | 36 | not available |
1Values are based on a temperature of 10°C, pH range of 6 to 9, and a free chlorine residual of 0.2 to 0.5 mg/L.
2Values are based on a temperature of 10°C, pH of 8.
3Values are based on a temperature of 10°C, pH range of 6 to 9.
Table 2. CT-values for the inactivation of Giardia cysts by various disinfectants
| Disinfectant | Inactivation (mg · min/L) | |||||
|---|---|---|---|---|---|---|
| 0.5-log | 1-log | 1.5-log | 2-log | 2.5-log | 3-log | |
| Chlorine1 | 17 | 35 | 52 | 69 | 87 | 104 |
| Chloramine2 | 310 | 615 | 930 | 1,230 | 1,540 | 1,850 |
| Chlorine Dioxide3 | 4 | 7.7 | 12 | 15 | 19 | 23 |
| Ozone3 | 0.23 | 0.48 | 0.72 | 0.95 | 1.2 | 1.43 |
1Values are based on a free chlorine residual less than or equal to 0.4 mg/L, temperature of 10°C, and a pH of 7.
2Values are based on a temperature of 10°C and a pH in the range of 6 to 9.
3Values are based on a temperature of 10°C and a pH of 6 to 9.
Reduction of disinfection byproducts
Disinfection byproducts (DBPs) are formed when disinfectants used in water treatment plants, particularly chlorine gas, react with bromide and/or natural organic matter such as decaying vegetation present in the source water. Different disinfectants produce different types and amounts of byproducts, some of which are potential health hazards. In the U.S., regulations have been established for levels of DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), bromate, and chlorite. THMs and HAAs are primarily the products of chlorine disinfection.
Ozone as a pre-oxidant enhances total organic carbon (TOC) removal during clarification and filtration. This results in lower TOC levels in the treatment effluent. Lower TOC levels reduce the chlorine demand and minimize DBP formation.
Ozone can be used in conjunction with granular activated carbon (GAC)-based biofiltration. Ozone oxidizes organic compounds so that they are more effectively metabolized by microbes resident on GAC filters. The resulting treatment process scours captured organics off the carbon's active surface — removing more TOC and lenghthening filter life.
Iron and manganese removal
Ozone Technology's Pressureless Ozonation Systems are particularly effective in the removal of iron and manganese compounds. Raw water often includes dissolved iron because of iron present in soil. When water containing colorless, dissolved iron is allowed to stand in a cooking container or comes in contact with a sink or bathtub, the iron combines with oxygen from the air to form rust. Clothing washed in water that contains iron may be stained a brownish color. In addition, iron may adversely affect the taste of beverages such as tea and coffee.
Manganese produces a brownish color in laundered clothing, leaves black particles on fixtures and, like iron, affects the taste of beverages, including tea and coffee.
The maximum contaminant levels (MCLs) for iron and manganese are 0.3 milligrams per liter (mg/l) and 0.05 mg/l, respectively. Iron and manganese in excess of the suggested MCLs usually cause discolored water and laundry, as well as stained plumbing fixtures.
Iron and manganese oxidation
Before iron and manganese can be filtered, they must be oxidized to a state in which they can form insoluble complexes. Oxidation involves the transfer of electrons from the iron, manganese, or other chemicals being treated to the oxidizing agent. Ozone is the most powerful oxidizing agent, as shown in these two equations:
H2O + O3 + Fe2+ → FeOH2+ + O2
Mn + O3 → MnO* + O2
Ozone oxidation followed by filtration is a relatively simple process:
- Ozone chemically oxidizes the iron or manganese (forming a particle), and kills iron bacteria and any other disease-causing bacteria that may be present.
- The filter then effectively removes the newly formed insoluble iron and manganese particles from solution.
Effective iron removal
Ozone can be a particularly effective agent in the iron removal process. When oxidized with ozone, iron particles generally stick together (coagulate) to form large flakes that can easily be filtered out in the water treatment process.
Ferrous - Water-soluble ferrous bicarbonate is often called clear water iron since it is not visible in poured water. It is found in water that contains no oxygen, such as groundwater and water from deep wells. Carbon dioxide reacts with iron in the ground to form water-soluble ferrous bicarbonate which, in the water, subsequently produces ferrous ions.
Ferric - Ferric iron is also known as red water iron. Ferric iron is ferrous iron that has been exposed to oxygen (oxidized), typically from the air. As carbon dioxide leaves the water, oxygen combines with the iron to form ferric ions. These oxidized particles are insoluble, generally visible in poured water, and can be removed from solution by simple mixed-media filters.
Bacterial Iron - Slime appearing in toilet tanks or fouling water filters and softeners is a good indication of the presence of bacterial iron. Sometimes described as iron bio-fouling, the iron bacteria problem is both complex and widespread. It attacks wells and water systems around the world in many aquifer environments, both contaminated and pristine. Treatment of bio-iron involves deactivating bacteria and destroying the associated slime.
Ozone lengthens filter life
The graph below shows how filters last longer with ozone.
The Historical Data line plots the average filter runs the plant was able to achieve using chlorine as the primary oxidant before iron "breakthrough" (the point at which the water coming out of the filter — and then on to customers — had an iron concentration of 0.3 ppm or greater (the point at which iron starts to become noticeable).
With Ozone, the same filter was able to both remove more iron (as evidenced by the lower average iron concentration) and do so for a longer period of time, resulting in fewer backwashes, lower electricity usage, and reduced labor costs.
Ozone lowers costs of treating iron-contaminated water
Taste, odor, and organic color control
Ozone Technology Pressureless Ozonation Systems are often the best solution for improving water's taste, odor, and color.
Ozone effectively and efficiently oxidizes hydrogen sulfide, MIB/Geosmin, and organic compounds that contribute to taste and odor problems.
Ozone removes organic color from contaminated water, often caused by tannins and lignins.
