Ozone is both a powerful oxidizer and effective disinfectant which makes it a natural fit for treating drinking water (i.e. public and private, wells, etc.) and municipal/industrial wastewater.
In 1785, Van Marum noticed that air near his electrostatic machine acquired a characteristic odor when electric sparks were passed. In 1840, Shonbein named the
substance, which gave off this odor, “ozone” from the Greek word “ozein” — to smell. In 1886 ozone was recognized as a disinfectant for water and in 1891 the first pilot plant in Germany proved ozone effective against bacteria. The first drinking water plant began operations in Nice, France, in 1906 and Nice is generally referred to as the birthplace of ozonation for drinking water treatment.
Today more than 2000 installations worldwide use ozone to treat drinking water and its use is increasing rapidly. Environmental concerns with the transport, storage, and disposal of chemicals combined with the health concerns with halogenated chemical byproducts (THM’s) make ozone a favorable alternative to halogen chemicals including chlorine.
Treating municipal and industrial wastewater with ozone was a key focus in the United States during the late 1970s and early 1980s. Today the use of ozone in wastewater treatment is accelerating rapidly due to both wastewater discharge regulations and the environmental concerns with halogenated chemicals (including chlorine) and the byproducts they produce.
Applications of ozone in water and wastewater treatment include the following:
1) Disinfection – Ozone effectively destroys a broad spectrum of microbes and pathogens (Organisms Killed by Ozone) including bacteria, Cryptosporidium, Giardia, Amoebae and all known viruses more rapidly than any other chemical.
Summary of Ct-Value Range for 99% Inactivation of Various Microorganisms by Disinfectants at 5oC
|Giardia Lamblla cysts||47-150||—||—||0.5-0.6|
|Giardia muris cysts||36-630||1400||7.2-18.5||1.8-2.0|
2) Taste, Odor and Color Removal – The powerful oxidation potential of ozone allows it to be effective in the reduction or elimination of taste, odor and color (including tannin).
3) Oxidation of Inorganics and Metals – Many metals can be reduced to very low, safe levels in water and wastewater through ozone oxidation.
Lab results have shown that ozone can convert nitrite ions to nitrate ions and remove the following metals at 99.5% or above: iron, manganese, copper, lead, arsenic, aluminum, cadmium, chromium, cobalt, zinc, mercury (complete removal at pH 4) and nickel (Coate, 1997). In addition, ozone oxidation can also be utilized to liberate organically bound heavy metals.
4) Oxidation of Organics – Organic contaminants can be reduced and/or removed utilizing ozone as an oxidizer.
Ozonation has also been shown to be effective in treating the following: acetic acid, butoxyethanol, isopropyl alcohol, Methyl-ethyl Ketone, Acetone, Aetyl Alcohol, Alycerol, Aropylene glycol, n-butyl acetate, formaldehyde, methacrylic acid, benzene benzyl alcohol, resorcinol, n-butyl phthalate camphor, para-phenylenediamine, styrene trecresyl-phosphate, xylene, butane, liquefied-petroleum-gas, mineral spirits, methylene-chloride, perchloroethylene, trichloroethylene, hydrogen cyanide, ammonium-hydroxide, ethanolamine, toluene, isobutane, propane, methyl-chloroform, amino-phenol, ammonia, ammonium-persulfate-phenacetin, ethylene tetracetic acid (EDTA), alkylated silicates, and non-ionic detergents (Coate, 1997).
Ozone can also be converted to hydroxyl radicals which are even more powerful oxidizers than ozone itself. Processes in which ozone is converted to hydroxyl radicals to achieve higher reaction rates are known as Advanced Oxidation Processes and can be utilized to treat many wastewaters.
Ozone has the following advantages over other chemical alternatives:
- Ozone is a very powerful oxidant (second only to fluorine) which is always generated on-site requiring no transportation or storage of dangerous chemicals.
- Ozone effectively destroys a broad spectrum of microbes and pathogens (Organisms Killed by Ozone) including bacteria, Giardia, Amoebae and all known viruses more rapidly than any other chemical (including chlorine compounds) and ozone is the only recommended primary disinfectant for Cryptosporidium.
- Ozone oxidizes organic and inorganic impurities and because it is a 50 percent stronger oxidizer than chlorine, ozone requires significantly less contact time to remove inorganic/organic compounds.
- Ozone’s powerful oxidation potential allows it to be effective in the reduction or elimination of taste, odor and color (including tannin).
- Ozone reactions (unlike halogen chemicals) do not produce halogenated disinfection byproducts such as trihalomethanes (THM’s) and ozone rapidly decomposes to oxygen leaving nothing behind.
- Ozone treated wastewaters do not contain chlorine or chlorinated disinfection byproducts, thereby making de-chlorination unnecessary. In addition, treatment of wastewater with ozone increases dissolved oxygen levels eliminating the need for effluent re-aeration.
- Ozone increases coagulation effectiveness and does not alter the pH of the water.
- Ozone systems can be highly automated and are very reliable.
In the United States, ozone has historically been used more frequently in large water and wastewater treatment systems. Ozone’s use in small or medium-sized systems, where it’s benefits could reach more people, has been restricted by the size, cost and reliability of ozone generating equipment.
The introduction of McClain’s “Ozone-on-Demand” systems has made ozone available for these smaller systems and applications. McClain focuses on assisting small and medium sized systems and facilities (public and private) in the use of ozone. Our systems are cost effective, highly reliable, can be designed and utilized in any size water or wastewater application. In addition, we take pride in assisting our water and wastewater clients with design, technical support and training in the use of our systems.