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Ozone Systems for Cooling Towers   


                                                              Tested and Proven at NASA

                                                                   SAVINGS EXAMPLE

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Traditional Cooling Tower Water Treatment versus Ozonation

Traditional cooling tower water treatment involves chemical treatment with a variety of metal compounds, organics, biocide, pH stabilizers, etc.  After only a few cycles, typically three or four, this water needs to be blown down.  However, the quality of the blowdown water is so poor that it cannot be recycled or recovered, and the cost, with sewer surcharges, plus the cost of the replenishment water will be significant factors in the operating cost.  The chemicals promote corrosion and do not fully prevent biofilm and scale build-up. Although chemicals can be somewhat effective biocides, bacteria in cooling towers mutate and become resistant to chemicals, which necessitates a changing cocktail of chemicals to counteract the bacteria’s newfound resistance.  Also certain bacteria, e.g. legionella, are protected from chemicals by the biofilm which forms in every chemically treated cooling tower.  In fact, the Center for Disease Control and Prevention proved that ozonation of cooling tower water killed Legionella bacterium in cooling towers faster and more completely for safer cooling tower operation. Contrary to chemical treatment, ozonation does not require any chemical adjustments of the water.  Ozone acts as an extremely effective disinfectant and biofilm and scale inhibitor, thus having to clean the chiller tubes to remove biofouling is no longer necessary.  Also, with ozonation, the cycle time can be increased, thus increasing the intervals between blowdowns, and because the blowdown water does not contain concentrated chemical residue, it may be discharged into the sewer with no sewer surcharges, now very common in most municipalities

 The Advantages of Ozone

Several companies offer ozone treatment apparatus for water cooling towers, and the advantages of ozone are generally well known. However, ozone, not optimally applied, also has some drawbacks.  After all, ozone treatment of cooling tower water began in the seventies, with only marginal success at best, and has been getting better and better in the ensuing thirty plus years.  Many technical articles, tutorial articles, and federal and state government studies and reports attest to this fact.  The most competent companies now can and do install amazingly successful systems that result in the full range of advantages sought for ozone treatment, including the complete elimination of biofilm and scale on heat exchangers.  The “secret” to obtaining the full range of advantages, and avoiding the potential drawbacks of ozonation is to maintain the exactly correct level of ozone, within a narrow, fluctuating band, determined by the constant monitoring of several tower water parameters and constant calculation of the optimum parameter levels to maintain, in addition to maintaining the pH within a proper band, proper fluid pressures in the sidestream piping, and water flow patterns. Only Clean Streams™ systems offer this Advanced Ozone Technology.

The Advantages of Ozone, Optimally Applied are:

  •  Very effective as a disinfectant—does not allow algae, bacteria or virus buildup

  •  Microorganisms cannot become resistant to ozone even after long exposure, like they can and do in response to most chemicals.

  •  Ozone permits truly chemical free cooling towers. It replaces disinfectants, dispersants, and inhibitors, so no chemical compounds to buy, store, apply, or dispose of.

  •  Improved safety because no stored chemicals

  •  Easier compliance with EPA and State regulations with no chemicals used

  •  Excellent biofilm removal

  •  Effective against Legionella, because not only is it a powerful biocide, but the biofilm, which protects Legionella and other bacteria and viruses, is removed.  Also effective against E.coli, Listeria, etc. for the same reason.

  •  Scaling is prevented, again because the biofilm is removed

  •  High efficiency of heat exchangers is maintained, because scaling and biofilm buildup is prevented

  •  Reduced costs to maintain the condenser unit (no scaling or biofilm)

  •  No chlorinated compounds are used, nor is excess ozone introduced, so there are very low corrosion rates

  •  No chemicals in the discharge (effluent), so there should be no sewer surcharge, a major savings in some municipalities.

  •  Many municipalities allow Ozone treated blowdown water to be discharged into storm drains, eliminating sewer charges altogether.

  •  In most cases a higher cooling water concentration factor is possible, typically twice as much, e.g. from four cycles to eight, further reducing operational (water) cost by reducing bleed-offs or blowdowns

  •  Lower operational costs, because there is high heat exchanger efficiency (lower electricity cost), no chemical purchase, storage, or application expense (lower material and labor costs), less maintenance (reduced labor cost), less frequent blowdowns, (lower water and sewer charges) and no sewer surcharge (still lower sewer costs)

  •  You will extend the useful life of your equipment

  •  Our Advanced Ozone Technology allows treatment of either municipal or well water.

 Who Will Benefit Most from Using Ozone?

  1. Installations at government (municipal, state or federal) institutions where the lowest bid for chemicals must be accepted, and is typically inadequate treatment for the application.
  2. Installations which are concerned about having a legionella outbreak
  3. Installations which have discharge restrictions or surcharges imposed by the municipal or state government.
  4. Installations in which tower water is contaminated by process water, with resulting biofouling problems.
  5. Installations in which maximum chiller efficiencies, minimum operating costs, and reduced maintenance are mandated.

 Return On Investment

ROI  has been obtained in from 6 to 36 months, with the period getting shorter as water and sewer charges escalate.  Intangibles, such as fear of a Legionella “incident” are further incentives to go the Ozonation route.

CATEC will be happy to discuss installed Clean Stream™ systems, e.g. at the Kennedy Space Center and at Army Research Laboratory in MD. or a  new Clean Stream™ system for you. Call us! Ask for Art Suma or Howard Taylor: you will be glad you did.

Clean Streams™ Ozone Systems for Cooling Water Treatment is a product of Zentox (


CASE STUDY:  Army Research Laboratory, Adelphi, MD

 In January, 2004, a Clean Streams™ system replaced the traditional chemical treatment program at the Army Research Laboratory in Adelphi, MD.  Clean Streams™ Ozone Treatment was selected for treatment of the cooling water to support their energy management plan.  This campus-like setting consists of multiple buildings that are supplied chilled water from a central chilled water plant.  This plant operates seven chillers with a combined cooling capacity of 7300 tons.  Each chiller has its own dedicated BAC cooling tower.  Prior to ozone, each system was treated individually.

 The Army Research Lab. System design included combining the basins of the seven cooling towers into two larger basins so that all towers are now treated with just two Clean Streams™ Ozone Systems. This design simplified the treatment approach, and has resulted in a very cost effective system.  Since startup, the cooling water cycles of concentration have been increased to eight cycles versus four on chemical treatment, leading to substantial water savings.  The cooling water is being maintained virtually bacteria free.  With this improved cleanliness, the high corrosion rates, which were a problem prior to the Ozone treatment, are reduced.  In addition, biofilm and scaling are controlled, which improves chiller efficiency, leading to energy savings and lower maintenance costs.


CASE STUDY: Virginia Power, One James River Plaza, Richmond, VA

      Ozone unit installed 12/96 resulted in:

  •  Reduced water use by 50%.

  •  Reduced tower clean-out intervals

  •  Chillers were not opened for two years: opened 1/98 and found to be clean

  •  Chillers have remained clean since startup.


             CASE STUDY: Vehicle Assembly Building, Kennedy Space Center


In January 2000, a Clean Stream™ system replaced the existing ozone treatment system on the Vehicle Assembly Building (VAB) and Launch Control Center (LCC) cooling towers with a state-of-the-art ozone water treatment system that is centered on the Clean Streams™ Ozone Transfer Process.  The cooling towers, a launch critical system, had been on ozone treatment since 1992, but the old ozone system had not performed to KSC standards for many years.

The VAB has chillers with a total of 10,000 tons capacity for HVAC.  The system has a volume of 240,000 gallons and is composed of four cells, each with a flow of 7,500 gpm.  The condenser system has an average annual loading of 35%.

 Water Conservation:

Cycles of concentration of the cooling tower were raised from 4 to 12, thus reducing blowdown and makeup water consumption.  Building water usage was reduced from 65,000 gal/day to 10,000 gal/day, a reduction of 85%.

 Microbiological Control:

The new Clean Streams™ ozone cooling water treatment system was powered up in April, 2000.  Following start-up, the towers are free of microbiological fouling, even with an increase in cycles of concentration and a decrease in city makeup water.

 Improved Operation:

After the upgrade to the Clean Streams™ system, the building air conditioning system was able to run, still at 36% avg. annual loading, with much lower operational costs (electricity, water, maintenance).

 Corrosion Control:

Corrosion coupons were installed in the system and corrosion rates began dropping as microbiological cleanup occurred.  Corrosion rates are continuing to stabilize, and are currently at less than 4 mpy on mild steel and less than 1 mpy on copper.

 Customer Response:

The primary contractor for this project at Kennedy Space Center is actively promoting the conversion of other towers at the facility to using ozone treatment.


                            SAVINGS EXAMPLE

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