Mixed Oxidants: Frequently Asked Questions What is the purpose of disinfectants in drinking water? Disinfectants are used initially to inactivate or kill bacteria and microorganisms in the raw water drawn from Lake Hartwell as part of the treatment process. In additon, chlorine is added to the finished water prior to introducing it into the distribution system to protect against recontamination that occurs in the distribution system through leaks and other compromises. The U.S. Environmental Protection Agency (EPA) and the SC Department of Health and Envornmental Control requires maintenance of at least 0.2 mg/L of chlorine residual leaving the treatment plant and at least a measurable trace residual at all points in the distribution system. My water is cloudy, is it still safe to drink? Yes, all drinking water maintains a sufficient disinfectant residual to ensure public health. Any cloudiness in the water is a result of mixed oxidants eliminating biofilms that may be present in the existing water system. Biofilm is a thin film-like layer created by bacteria that may develop in water distribution lines, cooling towers, and any other aqueous environment. Biofilm is resistant to chlorine and is difficult to remove once it starts. By eliminating any biofilm, mixed oxidants result in less bacterial contamination, reduced disinfectant requirements, and more durable disinfectant residuals to prevent recontamination. With less organics in distribution piping, fewer disinfection by-products are formed. Why change from something that has worked for over 40 years? Since the Anderson Regional Joint Water System water treatment facilities are located on Lake Hartwell near homes and and businesses, safety is an important consideration. On- site generation of mixed oxidants eliminates the transportation, handling, and storage of hazardous water disinfection chemicals like chlorine gas and concentrated bleach (sodium hypochlorite). In addition to providing a safer environment, mixed oxidants provide a water quality that is safer to drink. At the same doses and contact times as conventional chlorine, mixed oxidants have been shown in numerous laboratory studies to achieve a more thorough and more rapid inactivation of a wider range of microbes. Finally, the on-site generation allows us to have better control on the cost of water produced. Both chlorine gas and bulk hypochlorite have been increasing in cost over the last several years, substantially more than the rate of increase of the cost of salt and electricity, the key components of mixed oxidants. Does this mean that the existing chlorine gas disinfection system was bad or unhealthy? No, quite the opposite, the U.S. Surgeon General has stated that disinfection of drinking water primarily using chlorine gas has been the single biggest contributor to increased longevity and public health in the United States over the past 100 years. While potentially hazardous if released to the atmosphere; in minute quantities, chlorine gas is a highly effective and safe disinfectant. Global circumstances and the risk of accidental spill have led us to look for alternative methods of delivering the same benefits with less overall risk. What does on-site generation mean? Typically, the resulting chlorine disinfectant is packaged in cylinders (chlorine gas) or drums (sodium hypochlorite) and transported to the end user. In the 1970s, smaller electrolytic equipment that uses common salt in order to move the process on site, and eliminate the transportation and storage of hazardous chemicals became available. Over the last several decades, both the on-site generation process and the equipment availability have been refined and improved. Thus, only salt and electricity are delivered to the plant. This eliminates the need to transport through the community and store potentially hazardous chlorine gas at the plant-site. How are mixed oxidants produced? Mixed oxidants are generated using a process called electrolysis. In the process, an electric current is passed through a salt brine solution. The resulting products are a chlorine mixed oxidant solution and hydrogen gas. The hydrogen gas is vented and disposed. The dilute chlorine-mixed oxidant solution (1% compared to 5% for household bleach) is generated daily and stored at the plant for use through-out the day. The electrolysis of salt to generate chlorine has been practiced for over a century. MIOX technology capitalizes on the century-old practice of using salt electrolysis to generate chlorine disinfectant. What are mixed oxidants? The mixed-oxidant solution is a mixture of chlorine and other chlor-oxygen compounds that are generated electrolytically using salt, water, and power. Although the mixed- oxidant solution is measured and dosed as free available chlorine (FAC), it acts like a more active chlor-oxygen chemistry than traditional chlorine. In contrast to other chlorine technologies, mixed oxidants offer a superior disinfection efficacy, elimination of biofilm, a more durable chlorine residual, reduced formation of disinfection by-products (DBPs), and improved taste and odor. Moreover, mixed oxidants readily oxidize ammonia, sulfides, iron and manganese. Will mixed oxidants affect the taste of the water? Mixed oxidants break down odor causing compounds, such as phenols or organochloramines. Mixed oxidants appear to remove the musty odors of geosmin and methyl isoborneol (MIB) caused when the raw water source suffers algae blooms. Thus, by neutralizing odor-causing compounds without adding a chemical taste mixed oxidants result in significant reductions in taste and odor complaints. Are mixed oxidants safe? On-site generation of mixed oxidants uses only salt, water, and power as feedstocks. Neither the salt nor the mixed oxidant produced is classified as hazardous by the regulatory agencies. The concentration of the generated chlorine solution is below the Hazardous Communications Standard (HCS) safety threshold limit of 1 percent. Although hydrogen gas is evolved from the electrolytic process of on-site generation, automatic venting designs or air dilution systems safely vent this gas to the atmosphere. On-site generation has an excellent safety record, with more than 4,000 units, from a variety of manufacturers, installed worldwide. There are no hazardous chemicals used, transported, or stored with mixed oxidant on-site generation equipment. Is the process expensive? Will my water bill go up? The cost of operating an on-site generation system depends on the cost of salt and power. In general, the lifecycle cost of on-site generation is very competitive with chlorine gas alternatives, and is typically less than delivered hypochlorite and the advanced disinfection technologies of chlorine dioxide, ozone and UV. In the case of the Anderson Regional Joint Water System, our favorable cost of electricity has allowed us to generate disinfectant on-site for less unit cost than purchasing it in bulk, either as gas or liquid hypochlorite. With the the increasing cost trends in transporting chlorine gas, on-site generation should produce significant cost savings over the life of the system.