The benefits of using ozone in any water treatment system can be maximized by learning as much as possible about the water being treated and by knowing the properties and capabilities of ozone. Water treatment dealers need to understand what ozone does best so it can be applied properly and efficiently with satisfying results.

Ozone is certainly not the least expensive method available to treat a single water contaminant problem, but a thorough water analysis will likely show that more than one treatment challenge exists. Because ozone acts on such a wide variety of contaminants, its use can become quite cost effective if the total treatment process is considered. For example, a simple iron removal system can be purchased for about one-third the cost of an ozone system large enough to remove an equivalent amount of iron. However, because it is likely that iron is not the only problem, one ozone system can do the same job as several individual subsystems.

Once again, education plays a vital role in realizing the benefits of incorporating ozone into a water treatment system. To be successfully applied, ozone systems must be made simple enough to be cost effective, easy to install and operate, and require minimum maintenance. At the same time, they must be sophisticated enough to be reliable, electrically efficient and effective. Armed with the correct knowledge, the water treatment dealer will know what ozone does, how much is required for each application, and how to use it in conjunction with other components to provide complete water treatment systems.

Uses for ozone
zone effectively oxidizes a variety of waterborne contaminants without leaving an undesirable residual, adding to total dissolved solids (TDS) levels or causing radical shifts in pH. Ozone is used to achieve a number of water treatment goals, including disinfection, oxidation of inorganic contaminants such as iron and manganese and oxidation of organic micropollutants. Although less is known about the subject, ozone is also effective as a pretreatment to improve the performance of subsequent water treatment processes.

• Disinfection. Broadly defined as the inactivation of bacteria, viruses and parasites, ozone is very effective in eliminating many of these contaminants. E. Coli, Staphylococcus, Legionella pneumophila and the protozoa Giardia and Cryptosporidium are examples of microorganisms that are oxidizable by ozone. However, disinfection using ozone requires that a proper dosage is effectively dissolved into the water and that it is given an appropriate amount of contact time.
• Oxidation of inorganics. Ozone is commonly used to remove ferrous compounds and manganese from water. The problems normally associated with the presence of these metals are more aesthetic in nature than health-related. However, standards have been established for both in their soluble states because the growth of iron- and manganese-oxidizing bacteria can cause a deterioration of overall water quality. Ozone readily oxidizes both metals, but iron more easily than manganese.

  Ozone will oxidize all the iron present before attacking the manganese, a phenomenon that will affect the prescribed dosage and contact time. This is another reason to have a thorough knowledge of the water being treated. Also, water with high organic content will adversely affect ozoneís ability to act on inorganics, further affecting dosages and contact times.

• Oxidation of organics. Ozone has been used to treat color, taste and odor problems normally caused by the presence of organic materials in the water. The primary cause of color in natural waters are humic substances (decomposed plant and animal matter), and while methods for removing color such as ion exchange or microfiltration are effective, ozone is the most efficient of the oxidizers in performing this function. A treatment train involving ozonation and certain types of filtration can achieve 90-95% color removal efficiencies. In situations where ozone is being utilized for color removal, it can perform the added function of killing bacteria if traditional methods are ineffective due to bacterial fouling.

  Taste and problems originate from both inorganic and organic sources, but non-pathogenic organic compounds are the cause in most cases. Hydrogen sulphide, iron, copper and zinc are notable inorganic taste and/or odor culprits, while the responsible organics are often algae compounds. In most cases, treatment of taste and odor problems are solved through a multi-stage process. The process can vary depending on the nature of the compound(s) causing the problem, involving at least an oxidative stage (ozone, chlorine, potassium permanganate, etc.) followed by a non-oxidative stage (activated carbon, sand filtration, etc.).

• Particulate removal. Ozoneís ability to coagulate particulate matter has been a subject of debate for a long time. However, in the last fifteen years, the coagulating effect of ozone has been used successfully in modern water treatment plants. The introduction of ozone can have a wide range of secondary effects on coagulation, including improved total organic compound (TOC) and turbidity removal during subsequent treatment and a decrease in required dosages of the traditional coagulant.

Equipment Considerations
While point-of-entry (POE) water treatment is quite different from techniques used by large water treatment plants, correct placement of the ozone subsystem in POE applications is also important to maximize the effectiveness of ozone. The illustration included shows the components of a basic residential well water treatment system for iron, manganese and sulphide removal, including the location of the ozone subsystem.

Ozone is only one component part of a complete process - regardless of the application and water problem. Therefore, the ozone system selected is important. Some ozone equipment may seem so complicated that understanding its complexities is frustrating and time-consuming. Other systems may be simplified to the point of losing at least some of their effectiveness. Since each application will have unique treatment needs, look for ozone equipment with modular system components so they can be easily integrated into the total system.

Also, look for equipment that either includes or allows for the use of timers and oxidation reduction potential (ORP) controllers to help to keep the ozone systems easy to operate while maintaining maximum effectiveness. Finally, system integration is also important since several key components are involved in a complete ozone system, including air preparation, ozone generation, injection, contacting and off-gas elimination.

Since most water treatment applications involve a multi-step process, the point at which ozone is applied in the total system is also important. The table below illustrates the point of application for some of the more common problems encountered by modern water treatment plants.

Control of:	Point of Application	Ozone Dose
Fe/Mn Color Taste and Odor SOCs Particles Pathogens	Pre, Intermediate Intermediate Intermediate Intermediate Pre Pre, Post	Medium Medium to High High Medium to High Low Medium to High

Source: ìOzone in Water Treatment: Application and Engineering 1991.

Not a Cure-all
For customers of a water treatment dealer to get the best value from ozone, it is important to also understand what ozone doesnít do so well. Ozone is a powerful oxidizer, capable of disinfection and removing many organic and inorganic contaminants. However, other microorganisms are more effectively treated by other processes. For example, ozone is not effective in removing such constituents as calcium, magnesium, potassium, sulfates and nitrates. These are better handled by brine regeneration systems such as cation or anion resins. Also, sodium, arsenic and chlorides in small amounts are treated more effectively by reverse osmosis or distillation. If ozone is sold as a cure-all, the customer will be disappointed in the results of its use.

Again, the key is to know as much as possible about the water being treated by conducting a thorough water analysis before prescribing a water treatment system for any application. The better a professionalís knowledge, the more effective the prescribed system will be in treating problem constituents.

At the same time, ozone equipment manufacturers should insure that simple, reliable and effective ozone equipment is available to dealers. Ozone equipment installation and maintenance should not have to be rocket science - figuring out how to correct problem water is challenging enough!

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