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The form of oxygen known as ozonehas been recognized for nearly a centuryfor its powerful ability to disinfect water.Cooling tower water must be treated tolimit the growth of mineral and microbialdeposits that can reduce the heat transfer efficiency of the cooling tower. The useof ozone to treat water in cooling towers isa relatively new practice that is increasingin popularity, and it has good potential for use in the Federal sector. This Federal Technology Alert (FTA), one of a series onnew technologies, describes the use of ozone generation for cooling tower water treatment, and reports on field experienceof manufacturers, others who have treated cooling tower water with ozone, and its

benefits.

Energy-Saving MechanismA cooling tower ozone treatment sys-

tem compresses ambient air, then driesand ionizes it to produce ozone. Theozone is added to the circulating water inthe tower. Within minutes, it kills bac-teria, algae, and viruses that live in thetower s aqueous environment. The bene-fits of this action are numerous and impor-tant. Sometimes the organisms pose a

threat to human health for example, Legionella pneumophila , which causesLegionnaire s disease, is frequently found in cooling tower water. Moreover, micro-organisms tend to accumulate in a bio-film on the sides and components of thecooling tower system, impeding heattransfer efficiency, increasing energy con-sumption (as the system has to work harder), and adding to maintenance costs.A frequent problem is the buildup of scale, mineral coatings that adhere esp-

ecially well to the biofilm. Again theresulting buildup impedes system effici-ency and could affect human health.

Conventional cooling tower water treat-ment technologies include treatment withchemicals to remove microorganisms and scale, and blowdown of water to removeimpurities. These operations both add tothe cost of cooling tower operation and maintenance. Although some chemicaltreatment may be advisable even if anozone-generating system is installed (insome circumstances the ozone may causecorrosion of cooling tower components),the amount and subsequent costs can bereduced.

Ozone Treatment for Cooling

Towers New energy and water saving technology to reduce cooling tower operat-ing costs

FederalTechnology

Alert

A publication seriesdesigned to speed the

adoption of energy-efficient and renewable

technologies in theFederal sector

Prepared by theNew Technology

Demonstration Program

The U.S. Department of Energyrequests that no alterations bemade without permission in anyreproduction of this document.


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Florida. Environmental regulations madethe facility unable to discharge the blow-down to surface waters as had been donein the past. To reduce blowdown, anozone system was installed.

Operating at zero blowdown, the newsystem was 60% plugged in less than ayear and it was determined that an abso-lute zero blowdown operation was not

possible. However, concentration ratios(concentration ratio is an indicator of the

amount of blowdown from the system) of between 30 and 40 were eventuallyworked out and the facility significantlyreduced the blowdown. The annual water savings is 35.7 million gallons per year (135.1 million liters). The ozone system,costing an estimated $320,500, wasexpected to save $124,000/yr in water and chemical costs, providing a life-cycle costsavings of $800,000 with a savings-to-investment ratio (SIR) of 3.5.

A second case study is reported involv-ing an ozone treatment system installed in1994 for two cooling towers at the

Lockheed Martin Electronics and MissilesOcala (Florida) Operation. The towerssupport a variety of equipment for testingand production, as well as secondary cool-ing of heating, ventilating, and air-conditioning systems.

Installation of an ozone treatment unitat the Ocala facility took one day. After ayear of use, bacterial count in the water was reduced three orders of magnitude.Blowdown waste was reduced 90%. Thefeared corrosion impact from the ozonewas only half that resulting from treatmentwith chlorine. The net present value of the

ozone system exceeded $1 million with anSIR of 31.9.

Implementation BarriersThere are known barriers for imple-

menting the ozone cooling tower treatmenttechnology such as high cooling tower water temperature, hard water, and a highorganic load from the operating environ-ment. However, much excitement has

been generated around this technology for many reasons. Manufacturers and vendorssee a huge market and cooling tower oper-ators see the potential cost savings, envi-

ronmental benefits, and reductions inmaintenance and health hazards.Potential users should carefully review

their current and historic costs related tocooling tower water treatment and the per-formance of their associated coolingequipment. The guidance provided in thisFTA should help indicate whether it would

be advisable to consider this treatmenttechnology. Federal energy managers whoare familiar with ozone treatment systemsare also listed. The reader is invited to ask questions and learn more about the tech-nology by contacting the manufacturers

and contractors listed in the back of the FTA.

Technology SelectionThe ozone treatment for cooling towers

is one of many energy-saving technologiesto emerge in the last 20 years. The FTAseries targets technologies that appear tohave significant Federal-sector potentialand for which some Federal installationexperience exists. These FTAs seek toidentify if product claims are true or aresimply sales hype.

New technologies were identified

through advertisements for technologysuggestions in the Commerce BusinessDaily and trade journals, and throughdirect correspondence. Numerousresponses were obtained from manufactur-ers, utilities, trade associations, researchinstitutions, Federal sites, and other interested parties.

Technologies suggested were evaluated in terms of potential energy, cost, and environmental benefits to the Federalsector. They were also categorized asthose that are just coming to market and those for which field data already exist.Technologies classified as just comingto market are considered for field demon-stration through the U.S. Department of Energy s Federal Energy ManagementProgram (FEMP) and industry partner-ships. Technologies for which some field data already exist are considered as topicsfor FTAs. The ozone treatment for coolingtowers technology was found to havesignificant potential for Federal-sector savings and to have demonstrated energy-savings field experience.

Potential

During the last 20 years, technologicalimprovements have made smaller-scale,stand-alone commercial ozone generators

both economically feasible and reliable.Using ozone to treat cooling tower water isa relatively new practice; however, itsmarket share is growing as a result of water and energy savings and environmen-tal benefits relative to traditional chemicaltreatment processes. Analysis of the tech-nology indicates that it should have poten-tial for broad application in the Federalsector. In a properly installed and operat-ing system, bacterial counts are reduced,

with subsequent minimization of biofilm buildup on heat exchanger surfaces. Thereduction in energy demand, the increased operating efficiency, and the reduced maintenance effort provide cost savings aswell as environmental benefits and improved regulatory compliance withrespect to discharge of wastewater from

blowdown.

ApplicationThere are many reasons to consider

ozone: when chemical costs are high or chemical management is burdensome,

when water and sewer charges are high or

increasing, or when local regulationsrequire blowdown to be treated prior todischarge.

The technology is generally applicableto cooling towers associated with air-conditioning systems and light industrial

processes. Manufacturers claim to havetreated both wooden and metal towersranging in size from 60 to 10,000 tons.Four important technical criteria should beused when considering ozone treatment

technology: the quality of the make-up water

that is added to replace water lostthrough evaporation and blowdown(hardness and mineral content can

be a factor in ozone effectiveness)

the operating temperature of the heatexchanger (if it is too high, the ozonedissipates too rapidly to be effective)

the degree to which components of asystem are subject to corrosion (and thus potential frequent replacementor additional protection)

the operating environment of thecooling tower (excessive dirt and organic material will use up the ozone

before it can disinfect the water).A screening study and economic ana-

lysis (life-cycle cost) should also be part of the decision-making process. Coolingtowers associated with chillers for lightindustrial process cooling and commercialheating, ventilating, and air-conditioningare good candidates.

Field ExperienceCase studies by manufacturers,

research institutes, and government agen-cies have added to the growing popularityof ozone treatment systems as a demon-strably effective technology for coolingtowers. Equipment and installation costsare more than paid for by savings in water and chemical use, and by energy savingsfrom cleaner heat exchanger surfaces.

Turnkey costs for a typical ozone sys-tem capable of treating a 1,000-ton coolingtower are estimated to range from $40,000to $50,000. Although no utilities wereidentified that currently offer rebates for ozonation, a number have sponsored sem-inars and disseminated information, and some have sponsored field tests and com-

prehensive studies.

Case StudiesThe first case study examines a system

of four ceramic-filled concrete coolingtowers with a capacity of 2,500 tons(8,750 kW) each. These cooling towersreject heat from the air-conditioning sys-tem that provides temperature and humidi-ty control for Space Shuttle processing inthe Vehicle Assembly Building (VAB) at

NASA s Kennedy Space Center (KSC),


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Strategic EnvironmentalR&D ProgramThe Federal Government is the largest energy consumer in the nation. Annu-

ally, in its 500,000 buildings and 8,000 locations worldwide, it uses nearlytwo quadrillion Btu (quads) of energy, costing over $11 billion. This repre-sents 2.5% of all primary energy consumption in the United States. TheFederal Energy Management Program was established in 1974 to providedirection, guidance, and assistance to Federal agencies in planning andimplementing energy management programs that will improve the energyefficiency and fuel flexibility of the Federal infrastructure.

Over the years several Federal laws and Executive Orders have shapedFEMP's mission. These include the Energy Policy and Conservation Act of 1975; the National Energy Conservation and Policy Act of 1978; the FederalEnergy Management Improvement Act of 1988; and, most recently, ExecutiveOrder 12759 in 1991, the National Energy Policy Act of 1992 (EPACT), andExecutive Order 12902 in 1994.

FEMP is currently involved in a wide range of energy-assessment activities,including conducting New Technology Demonstrations, to hasten the penetra-tion of energy-efficient technologies into the Federal marketplace.

Federal Energy Management Program

The Strategic Environmental Researchand Development Program, SERDP, co-sponsor of these Federal TechnologyAlerts, was created by the NationalDefense Authorization Act of 1990(Public Law 101-510). SERDP's primarypurpose is to "address environmentalmatters of concern to the Department of Defense and the Department of Energythrough support for basic and appliedresearch and development of technolo-gies that can enhance the capabilities of the departments to meet their environ-mental obligations." In 1993, SERDPmade available additional funds toaugment those of FEMP, for the purposeof new technology installations andevaluations.

About the Federal Technology AlertsThe Energy Policy Act of 1992, and

subsequent Executive Orders, mandatethat energy consumption in the Federalsector be reduced by 30% from 1985levels by the year 2005. To achievethis goal, the U.S. Department of

Energys Federal Energy ManagementProgram (FEMP) is sponsoring aseries of programs to reduce energyconsumption at Federal installationsnationwide. One of these programs,the New Technology DemonstrationProgram (NTDP), is tasked to acceler-ate the introduction of new energy-saving technologies into the Federalsector and to improve the rate of technology transfer.

As part of this effort, FEMP, in a

joint venture with the Department of Defenses Strategic EnvironmentalResearch and Development Program(SERDP), is sponsoring a series of Federal Technology Alerts (FTAs) thatprovide summary information oncandidate energy-saving technologiesdeveloped and manufactured in theUnited States. The technologiesfeatured in the Technology Alerts have

already entered the market and havesome experience but are not in generaluse in the Federal sector. Based ontheir potential for energy, cost, andenvironmental benefits to the Federalsector, the technologies are considered

to be leading candidates for immediateFederal application.

The goal of the Technology Alertsis to improve the rate of technologytransfer of new energy-saving tech-nologies within the Federal sector andto provide the right people in the fieldwith accurate, up-to-date informationon the new technologies so that theycan make educated judgments onwhether the technologies are suitablefor their Federal sites.

Because the Technology Alerts arecost-effective and timely to produce(compared with awaiting the resultsof field demonstrations), they meetthe short-term need of disseminatinginformation to a target audience ina timeframe that allows the rapiddeployment of the technologiesandultimately the saving of energy in theFederal sector.

The information in the TechnologyAlerts typically includes a descriptionof the candidate technology; theresults of its screening tests; a descrip-tion of its performance, applicationsand field experience to date; a list of

potential suppliers; and importantcontact information. Attached appen-dixes provide supplemental informa-tion and example worksheets on thetechnology.

FEMP sponsors publication of theFederal Technology Alerts to facilitateinformation-sharing between manufac-turers and government staff. Whilethe technology featured promises sig-nificant Federal-sector savings, theTechnology Alerts do not constitute

FEMPs endorsement of a particularproduct, as FEMP has not indepen-dently verified performance dataprovided by manufacturers. FEMPencourages interested Federal energyand facility managers to contact themanufacturers and other Federal sitesdirectly, and to use the worksheets inthe Technology Alerts to aid in theirpurchasing decisions.


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For More Information

FEMP Help Desk(800) 363-3732International callers please use (703) 287-8391Web site: http://www.eren.doe.gov/femp/

General Contact

Ted CollinsNew Technology Demonstration ProgramProgram Manager

Federal Energy Management ProgramU.S. Department of Energy1000 Independence Avenue, SW, EE-92Washington, DC 20585(202) 586-8017Fax: (202) [email protected]

Steven A. ParkerPacific Northwest National LaboratoryP.O. Box 999, MSIN: K5-08Richland, Washington 99352(509) 375-6366

Fax: (509) [email protected]

Technical Contact

Steven A. ParkerPacific Northwest National LaboratoryP.O. Box 999, MSIN: K5-08Richland, Washington 99352(509) 375-6366Fax: (509) [email protected]

Produced for the U.S. Department of Energyby the Pacific Northwest National Laboratory

Reprinted August 1998

ozonio em torres de resfriamento

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