It has been almost one month since we were in Orlando for the Water Quality Assn. Convention & Exposition, and we keep thinking back to our...
Knowing the basics and where to look for more information
Ozone, O3, a triatomic gaseous form of oxygen, is an unstable molecule that is naturally occurring in nature. It is known as the world’s most powerful commercially available disinfectant and is used in a variety of industries, from drinking water to industrial water treatment to food processing.
Disinfection. Ozone destroys viruses and parasites such as Giardia and Cryptosporidium. A U.S. EPA technology fact sheet notes that ozone’s disinfection mechanisms include “direct oxidation/destruction of the cell wall, reactions with radical byproducts of ozone decomposition, damage to the constituents of the nucleic acids and breakage of carbon-nitrogen bonds leading to depolymerization.”
Chemical oxidation. With its unstable third oxygen atom, ozone is a highly powerful oxidizing agent. It is particularly effective against inorganics like iron, manganese and sulfide ions. Taste- and odor-causing organic materials are also oxidized by ozone, as is wood pulp in the pulp and paper bleaching process.
Decomposition. Ozone’s reactivity means that it decomposes rather quickly around room temperature conditions. At 20°C and pH 7, ozone’s half-life is about 24 minutes in potable tap water.
While ozone was considered a “chemical curiosity” after its 18th century discovery, its value was quickly engaged by the scientific community. In 1906, ozone was used for drinking water treatment in Nice, France. Ozone took a back seat to chlorine after World War I expansion of industrial chemicals, but it proved to be an effective alternative to chlorine across many applications.
Ozone technology gained momentum in the 1970s with increasing scrutiny regarding pollution and with the advent of contamination problems in the bottled water industry. The year 1973 saw the inception of the International Ozone Association (IOA). The IOA is a collection of engineers, scientists, manufacturers and industry professionals who work together to act as a clearinghouse for ozone technology and ozone application and regulation resources. As a nonprofit educational association, it is a “vehicle and authority for the global gathering, dissemination and summit on ozone information.”
Ozone is applied in a diverse array of industries, including drinking water, food processing, agriculture/aquaculture, cooling towers, semiconductors, laundry and air treatment, and many more. These industries all have different but overlapping regulations at the federal, state and industry levels. For many industries, there aren’t specific regulations for ozone use but, rather, a general acknowledgement of ozone as an optional alternative disinfectant to chlorine or other chemicals, and one that should be applied according to its chemical properties.
As more technology and research become available, regulations and public safety issues often end up directing municipalities and businesses toward ozone. Ozone is already acknowledged by the EPA to meet the most current and future Clean Water Act rules, according to Paul K. Overbeck, executive director of the IOA.
“Ozone is the best available technology for some specific water quality issues faced by utilities,” Overbeck said. “So, if the utility is faced with a source water with high levels of Cryptosporidium, then ozone and/or UV is the best available technology.”
When issues and outbreaks come up, such as bottled water recalls or the recent E. coli contaminants in raw spinach, the specificity afforded by regulatory scrutiny pushes standards to effective solutions such as ozone.
Many industrial organizations fall under federal regulatory umbrellas established by the EPA and subsequently the U.S. Food and Drug Administration (FDA) and U.S. Department of Agriculture. One overarching regulatory body that applies to any industry in which ozone is being applied in a labor setting is the U.S. Department of Labor’s Occupational Safety & Health Administration (OSHA).
The FDA’s maximum allowed ozone concentration in the air for residential areas is 0.05 ppm ozone by volume. For work environments, OSHA’s Permissible Exposure Limit for General, Construction and Maritime Industry is a 0.1 ppm time-weighted average (0.2 mg/m3). OSHA’s 15-min exposure limit is 0.3 ppm. OSHA further breaks down the regulation with Threshold Limit Values: 0.05 ppm for heavy work, 0.08 ppm for moderate, 0.10 ppm for light work, and any workload under two hours is 0.20 ppm. OSHA’s regulations are a good example of a framework that is put in place for occupational safety that makes distinctions for different practical exposure levels.
In 1982, ozone was declared “Generally Regarded As Safe” by the FDA, meaning it can be used in food products. This also applies specifically to bottled water, which also is under regulation by the EPA, allowing a residual dissolved ozone concentration of 0.4 mg/L. Title 21 of the Code of Federal Regulations under Part 165 describes the physical, chemical and other parameters for ozone in bottled water as a food product.
According to the Federal Register for Secondary Food Additives, “Ozone (CAS Reg. No. 10028-15-6) may be safely used in the treatment, storage, and processing of foods, including meat and poultry.” These developments occurred after a 2001 Food Additive Petition, Overbeck said.
The FDA further recognized ozone as a Good Manufacturing Practice for bottled water, with a minimum treatment of 0.1 mg/L.
In drinking water, dissolved ozone may oxidize bromide ions, naturally present in some source water, to bromate during the required contact time for microorganism disinfection. The maximum concentration limit is 10 µg/L for bromate as a disinfection byproduct, as of the January 2001 Disinfection/Disinfection Byproduct Rule.
A general recommendation is that with ozone disinfection, treatment plants that have raw water containing 60 µg/L of bromide or less will not face bromate problems. Some key steps can be taken to resolve bromate issues, including lowering the raw water pH and decreasing the water temperature. The most effective step by far is to maintain the system’s minimum dissolved ozone concentration. Engineering the correct contact time using ozone monitors and controls is part of a successful ozone installation. As with any ozone application, proper engineering, process control and communication will go a long way toward meeting regulations and preventing problems.
Trade association membership is one of the best ways to stay on top of the latest regulations. Not only is their access to information much greater than an individual could leverage, but these organizations also can be proactive with regards to supporting the development of legislation and regulations by supplying relevant technical and application information.
The FDA adopts regulations handed down by the EPA in applicable areas, and trade organizations such as the Water Quality Association, International Bottled Water Association (IBWA), American Water Works Association, Water Environment Federation and International Dairy Foods Association all have their own guidelines and good manufacturing principles based on federal regulations.
Taking advantage of industry-driven guidelines allows members to stay ahead of the game as regulations develop. For example, the IBWA, while not a regulatory agency, offers a manual titled “The IBWA Plant Technical Reference Manual,” covering various guidelines, standards, and recording and reporting protocols.
L. Joseph Bollyky, Ph.D., an ozone industry consultant, wrote, “Since ozone treatment has become such a key process for the water bottlers, they need to stay current with the advances in the technology and the improvements in the ozone treatment process. In addition, they must follow and review the regulatory and procedural changes in FDA, EPA and IBWA standards.”
For ozone-specific information, the organization that supports some of the aforementioned associations and more with relevant regulatory information is the IOA.
“By putting the proper technical information in their hands, it allows ozone a greater opportunity to be used by the public to meet specific treatment goals,” Overbeck said. “You’ve got something together that is documentable and verifiable.”
The IOA has put representatives on regulation committees all the way up to the EPA Regulations Committee for the Safe Drinking Water Act.
The issue of ozone controls is one of the most important factors in any ozone application. With proper ozone engineering, dosing and off-gas controls, issues such as ozone exposure and bromate levels are easily mitigated or resolved. Further, the process of evaluating and applying ozone controls to an installation is part of the value offered by members of the IOA, who are equipped with the latest knowledge and resources.
Based on those efforts, it is foreseeable that those industry-driven guidelines will help direct regulations in the future. For more information on the regulatory bodies and trade associations, be sure to do some research online (see Figure 1).