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A NATIONAL CLEARINGHOUSE FACT SHEET

Summary New goals for disinfection byproducts (DBP) and for microbial inactivation will increase the need to consider new disinfection technologies. Ozone is an attractive alternative. This technology has evolved and improved in recent years, thereby increasing its potential for successful application. It is important to note that ozone, like other technologies, has its own set of advantages and disadvantages that show up in differing degrees from one location to the next.

What is ozone? • Decays rapidly in water, avoiding any undesir Ozone is a colorless that has an most able residual effects; often described as the smell of after a • Removes color, , and odor; and electrical thunderstorm. Some people also refer • Aids coagulation. to the odor as similar to the smell of watermel-

ons. Ozone (O3) is an extremely unstable gas. Limitations Consequently, it must be manufactured and used The use of ozone to treat water has some onsite. It is the strongest oxidant of the common limitations: oxidizing agents. Ozone is manufactured by pass- ing air or through two electrodes with high, • Toxic ( is proportional to alternating potential difference. and exposure time); • Cost of ozonation is high compared with What regulations govern ozone? chlorination; In the next century, small water systems will • Installation can be complicated; need to use disinfection methods that are effective • Ozone-destroying device is needed at the for killing without forming excessive exhaust of the ozone-reactor to prevent toxicity DBP. Disinfection byproduct compliance is more and hazards; likely to be a problem for small water systems • May produce undesirable and treating water than for those treating ketones by reacting with certain organics; because sources tend • No residual effect is present in the distribution to contain more natural organic that forms system, thus postchlorination is required; byproducts when mixed with . • Much less soluble in water than ; thus In August 1997, the U.S. Environmental Protect- special mixing devices are necessary; and ion Agency (EPA) listed ozone as a “compliance’’ • It will not oxidize some refractory organics in the requirements of the Surface Water Treatment or will oxidize too slowly to be of practical Rule for all three sizes of small drinking significance. water systems. Disinfection Advantages Design of an ozone system as primary treatment Using ozone to treat water has many advantages, should be based on simple criteria, including including the following: ozone contact , competing ozone demands, and a minimum contact time (CT) to • Possesses strong oxidizing power and requires meet the required cyst and viral inactivation short reaction time, which enables the germs, requirements, in combination with EPA recom-

including , to be killed within a few mendations. FOURPAGE OF ; • Produces no taste or odor; Systems that need to provide CT to comply with one • Provides oxygen to the water after disinfecting; the Ground Water Disinfection Rule, but are also • Requires no chemicals; having problems with DBP or maintaining distri- • Oxidizes and ; bution system residuals, should consider using • Destroys and removes ; ozone as the primary and then chlo- • Reacts with and removes all ; ramines for distribution system protection.

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PAGE OF FOUR considered in planning. in considered be should needs these Therefore, practices. past with compared as required be may CT and dose ozone in increase significant a that indicate data Available application. its of aspect this in interest a chemical reaction. reaction. chemical a in relation weight the and produced are or bine com- elements chemical which in proportions the fecting disin- of capable be to observed been has Ozone removal to the chemical transformation transformation chemical the to leads removal This (SOC). chemicals organic synthetic many remove can processes ozonation advanced or Ozone Chemicals Organic Synthetic of Elimination treatment. downstream and ozone of choice optimum the determine to quired re- be may experimentation pilot-scale possibly and Analysis system. treatment a designing to prior considered carefully be to need treated, be to water source the as as compounds, odor and taste of cause the Again, reliability. and efficiency treatment odor and taste increase greatly can tion, filtra- (GAC) activated granular especially processes, treatment downstream other with tion combina- in ozone, that observed been also has It scavengers. from free relatively is water the when especially problems, odor and taste for water treating in effective be can ozone that shown been water.has finished It in less or 3 be () number threshold the that recommend ions WaterDrinking Regulat- Secondary National The Odor and Taste of Control decrease. can demand chlorine final the that such modified is structure organic the sufficient, is dosage ozone the when that note to interesting is It high. very be can color for goals treatment reach to order in applied be to dosages ozone The moval. O mg 3 to 1 of doses ozone authors, different to According . fulvic and humic with ozone of reactions the review to useful is it , natural in color of cause primary the are substances humic Because Abatement Color O mg 2.20 of stoichiometry theoretical a to sponds corre- (Mn) manganese of form soluble color.This pinkish a water gives which permanganate, of formation the to will ozone of doses Excessive added. is chlorination or ation ozon- if complaints iron have may (mg/L) liter per milligrams 0.1 above levels iron have that systems Groundwater content. organic low with water in and groundwater in manganese and iron oxidize readily can it that such is ozone of rate reaction and potential oxidation-reduction standard The Removal Manganese and Iron O 3 /mg Mn. Stoichiometry is the determination of determination the is Stoichiometry Mn. /mg z o 3 /mg C lead to almost complete color re- color complete almost to lead C /mg n e , and there is significant is there and , in pilot studies incorporating the proper controls. proper the incorporating studies pilot in evaluated critically be should effects ozonation pre- the aid, coagulant a as ozone of use the water.considering all Whenever with observed be not may ozone of effects coagulating the Finally, effects. direct ozone’s of evaluation separate the permitting controls incorporate to careful be must one trihalomethanes), example, (for DBP of removal the studying when Also, absorbtion. (UV) or removal color on solely based are data the when matter organic of removal proved im- claiming studies of wary be must one son, rea- this For macro-. organic on effects oxidative direct any beyond go ozone of effects coagulating the that understand to important is It Coagulation on Effects (CO dioxide carbon into oxidation complete to lead theoretically can transformation Such ucts. byprod- nontoxic or toxic into these of the earlier versions of this technology. this of versions earlier the had than maintenance cleaning-related less require and cleaner run to said therefore is ment treat- Ozonation systems. air-feed ambient than rather systems, feed oxygen purity high of use include technology ozonation in advancements However,recent substantial. fairly be may cleaning system for requirements time Personnel Requirements Personnel byproducts. chlorine the for those than less are products new the for concerns the as long as achieved is benefit disinfection, equivalent Assuming acids. carboxylic and ketones, aldehydes, as such byproducts, own its produces Ozonation . containing waters source in concern major a are byproducts Brominated byproducts. undesirable other of formation the to lead could and results ozonation affects significantly quality water However,raw treatment. chlorine of practice the in inherent organics halogenated of formation the avoid to ability its of because interest much generated has ozonation of use alternative The Byproducts , mobile e.g., zooplankton, certain inactivating of capable also is Ozone growth. its limits or algae some on effect lethal a has dioxide, chlorine or chlorine as such oxidant, other any like Ozone, Removal Algae pounds through stripping. through pounds com- volatile of loss and formation the or acids) amino of decarboxylation example, (for mation (TOC) is due either to a small degree of CO of degree small a to either due is (TOC) carbon organic total in reduction observable Any treatment. water in case the rarely is however,this by and filtration. filtration. and flocculation by removed are they before inactivated be first must TWELVE1999 DECEMBER • Notholca caudata. Notholca Such organisms Such 2 for- 2 ); No Residual Ozone contacting for disinfection has typically Ozone will not provide a disinfecting residual been accomplished in deep, multistage contac- that protects finished water in the distribution tors that employ fine bubble diffusers. Newer system. Therefore, the role of chlorine as a disin- alternatives have emerged that provide an option fecting agent is not entirely replaced, and its use for small systems through the use of side-stream in either the free chlorine or chloramine form will injection technologies that eliminate the need for be required for this purpose in many locations. fine bubble injection. Package units are available that include a gas separator that fuses and elimi- Process and Equipment nates excess gas that results from ozone addition The basic elements of an ozone system include and a venturi jet that is used to inject and blend ozone generation, feed gas preparation, ozone the ozone with a feed stream. These sys- contacting, and ozone off-gas destruction compo- tems allow the alternative of injecting ozone into nents. While many of these components can an enclosed vessel or a pipe. Note that materials involve a high degree of sophistication in large need to be compatible with ozone. One possibility facilities, less complex alternatives are available in this regard is the use of . Several for smaller systems. Figure 1 other contacting configurations, including turbine (see below) shows the five basic components of an mixers, have been developed and may provide ozonation system. To insure effectiveness and benefits as well. safety simultaneously, all components must be taken into account when designing/ installing an ozone Figure 1. Basic Components of an Ozonation System system. Central to the ozona- tion system is the ozone generator itself, which in turn is connected to an appropriate power supply. Electrical Power Supply H O 2 Destruction Instrumentation and controls for ensuring the effective and safe operation of the total system may be added to the five-component system shown in Figure 1.

Gas Preparation Ozone Generator Ozone Contactor Feed Gas Preparation The feed gas preparation com- ponent is critical, as a high- Source: “Ozone Treatment of Small Water Systems”1999. quality gas stream is required for the generator to perform Ozonated Water properly. This requires a gas stream that is low in moisture and . Exhaust Gas Destruction In older air-feed systems, the feed gas prepara- Ozone off-gas destruction is the final major com- tion systems for small systems tended to rely on ponent in the ozonation process. This system is high-pressure compressors that produce a pres- required to remove ozone from spent off-gas surized feed stream, which is easier to dry and streams, which are collected and treated prior can accom- modate simpler, less maintenance- to into the . Both catalytic intensive drying devices than were typically and thermal destruction devices are used for this applied in larger systems where lower-pressure purpose or by passage through GAC. compressors are typically used. How safe is ozone? Alternatives for application of oxygen-rich feed gas EPA notes that ozonation technology requires streams have also emerged for small system appli- careful monitoring for ozone leaks, which pose cations in recent years. These include purchasing a hazard in the work place. As with any other oxygen and using small package oxygen- chemical, the Occupational Health and Safety generation systems that are based on pressure Administration (OSHA) has established maximum swing adsorption. The use of these oxygen-enriched contaminant inhalation guidelines for ozone feed streams allows improved electrical efficiency in the work place. Ozone concentration of 0.1 part

in ozone generation and yields a product stream per million inhaled during an eight hour work FOURPAGE OF with a higher ozone content. in a work area is the maximum limit set by OSHA regulations. three Ozone Contactors Since ozone is only partially soluble in water, once it has been generated it must contact water to be treated. Many types of ozone contactors have been developed for this purpose.

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PAGE OF FOUR (1) American WaterAmerican Works1993. (1) Association. information? more find I can Where (2) Budd, G.C., G.S. Logdson, and B.W. Long. B.W.Long. and Logdson, G.S. G.C., Budd, (2) (3) Collins, M.R. 1998. M.R. Collins, (3) (4) International Ozone Association. 1999. Association. Ozone International (4) of the above numbers or contact him via e-mail at e-mail via him contact or numbers above the of one at Lahlou call topics, suggest to or sheet, fact this about comments information, further For Webat our site from sheets fact download or 293-4191. (304) or 624-8301 (800) at [email protected] at online order also Youmay NDWC the order,call To added. however,free;be are may sheets charges fact postal of copies Additional #DWBLPE84 item Ozone, Brief: Tech • #DWPSPE82; Wateritem Drinking Systems, Small for Technologies Treatment Brief: Tech • #DWBLPE81; item Filtration, Membrane Brief: Tech • #DWBLPE74; item Sheet, Fact WaterMeasures • Conservation #DWBLPE70; item Removal, Manganese and Iron Brief: Tech • #DWBLPE67; item Softening, Lime Brief: Tech • #DWBLPE65; item Management, Residuals Water Brief: Treatment Tech • #DWBLPE63; item , Package Brief: Tech • #DWBLPE59; item Removal, Organics Brief: Tech • #DWBLPE56; item Demineralization, and Exchange Ion Brief: Tech • #DWBLPE52; item Control, Brief: Tech • #DWBLPE50; item Filtration, Brief: Tech • #DWBLPE47; item Disinfection, Brief: Tech • items. popular very these writes and information, compiles Ph.D.,researches, Lahlou, Mohamed Specialist Assistance Technical newsletter Water(NDWC) Drinking Clearinghouse National the in feature regular a been have sheets fact treatment water drinking Briefs,’’ “Tech Technology, Operations, and Economics. and Operations, Technology, Systems: Small Waterin Drinking Safe G.F. Craun, and N. Hearne, eds. Hearne, N. and G.F.Craun, Cotruvo, J.A. Irradiation.’’ Ultraviolet and Ozone Dioxide, Chlorine of “Overview 1999. WaterAmerican WorksDenver: Association. Controlling Disinfection By-Products Disinfection Controlling Raton: CRC Press LLC. Press CRC Raton: Workshop. State-of-the-Art Technologies: Treatment Ozone Association. Ozone International Stamford: France. Poitiers, in Water Treatment. in (AOPs) Processes Oxidation Advanced and Ozonation on Conference Regional Association. Denver: American WaterAmerican WorksDenver: Applications and Research and Applications Small Systems WaterSystems Small Have you read all our Techour Briefs? all read you Have

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www.ndwc.wvu.edu. On Tap On [email protected]. (7) Vigneswaran, S. and C.Visvanathan. 1995. C.Visvanathan. and S. Vigneswaran, (7) (6) Rice, R.G., P.K. Overbeck, and K. Larson. Larson. K. and P.K.Overbeck, R.G., Rice, (6) Brink. D.R. and Reckhow, D.A. B., Langlais, (5) (8) U.S. Environmental Protection Agency. 1998. Agency. Protection Environmental U.S. (8) Economics and Operations, Technology, Systems: Small Hearne, eds. Hearne, N. and F.Craun, G. Cotruvo, A. J. Systems.’’ Water Small of Treatment “Ozone 1999. Publishers. Lewis and Foundation 1991. Water Treatment Processes: Simple Options Simple Processes: WaterTreatment Boca Raton: CRC Press, Inc. Press, CRC Raton: Boca Surface Water and Total Coliform Rules. Coliform Total WaterSurfaceand and Engineering and Water and Drinking Water.WaterDrinking and Ground of Office Washington,EPA DC: for Technologies Treatment System Small TWELVE1999 DECEMBER • for more than four years. NDWC years. four than more for Ozone in Water Treatment: Application Waterin Treatment: Ozone . Boca Raton: CRC Press LLC. Press CRC Raton: Boca . Providing Safe Drinking Waterin Drinking Safe Providing . Denver: AWWADenver: . Research .