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Prepared for the U.S. General Services Administration and theU.S. Department of EnergyBy the National Renewable Energy LaboratoryDECEMBER 2018Demonstration and Evaluation of anAdvanced Oxidation Technology forCooling Tower Water TreatmentJesse Dean (NREL)Dylan Cutler (NREL)Gregg Tomberlin (NREL)James Elsworth (NREL)ared for the U.S. General Services Administration and theU.S. Department of Energy

DisclaimerThis document was prepared as an account of work sponsored by the United States Government. While thisdocument is believed to contain correct information, neither the United States Government nor any agencythereof, nor the National Renewable Energy Laboratory, nor any of their employees, makes any warranty,express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, or represents that its use would not infringe privatelyowned rights. Reference herein to any specific commercial product, process, or service by its trade name,trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, orfavoring by the United States Government or any agency thereof, or the National Renewable EnergyLaboratory. The views and opinions of authors expressed herein do not necessarily state or reflect those ofthe United States Government or any agency thereof or the National Renewable Energy Laboratory. Fundingprovided by the U.S. General Services Administration.The work described in this report was funded by the U.S. General Services Administration and the U.S.Department of Energy] under Contract No. 47PA0117C0009.AcknowledgementsGSA's Proving Ground: Kevin Powell - DirectorGSA Region #8 - Doug Baughman - Energy Management Specialists / OFM, Tyler Cooper – MechanicalEngineerTenfold Information Design Services: Andrea SilvestriNational Renewable Energy Laboratory: Michael Deru, Kosol KiatreungwattanaFor more information contact:Jesse DeanSenior EngineerNational Renewable Energy LaboratoryEmail: [email protected]’s GPG program and DOE’s High Impact Technology (HIT) Catalyst program enable federal andcommercial building owners and operators to make sound investment decisions in next generationbuilding technologies based on their real-world performance.DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN Tii

Executive SummaryThis GSA Proving Ground project assessed the performance of an alternative water treatment (AWT)system manufactured by Silver Bullet for a 500-ton cooling tower at Building 95, at the Denver FederalCenter in Denver, Colorado. Cooling tower water consumption is one of the largest potable water loadsin commercial buildings in the United States, as more than 28% of water use is from heating and coolingsystems (EPA n.d.). A cooling tower uses an evaporative cooling process to reject heat to theatmosphere from a water-cooled chilled water plant. The continuous evaporation of water from thecondenser leaves behind the natural mineral content it carried (silica, calcium, magnesium, chloride).Thus, the remaining condenser water will have an ever-increasing concentration of impurities as morewater evaporates. These impurities will eventually precipitate out (because water can hold only somuch), resulting in solid precipitate. This solid precipitate is commonly called scale and collects onsurfaces, inhibiting performance. Typically, cooling tower water is treated using three methods: addingscale inhibitors that allow water to hold a higher concentration of minerals, using corrosion inhibitorsthat decrease corrosion in piping systems, and introducing biocides and algicides that mitigate biologicalgrowth in an open-air cooling tower.In addition to chemical treatments, a portion of the cooling tower water is typically drained as towerblowdown, and the tower is refilled with fresh makeup water. This reduces the chemical and mineralconcentration of the remaining condenser water. It also reduces the cycles of concentration of thecooling tower and increases annual cooling tower water usage. GSA operation and maintenanceprocedures require that cooling towers have a cycle of concentration of 2 or greater. A higher cycle ofconcentration correlates with less blowdown and reduced makeup water consumption for the coolingtower.The AWT technology evaluated at Building 95 at the Denver Federal Center is a nontoxic photochemicalbased cooling tower water treatment technology promoted as a simpler water treatment technologythat uses an advanced oxidation process to treat cooling tower makeup water. It pulls air from thesurrounding environment, which then passes through patented sleeves that contain ultraviolet lampsand other proprietary components that modify the ambient air, creating negatively charged oxygenatoms. These atoms diffuse into the water, forming highly reactive hydroxyl and other radicals. Thehydroxyl radicals and other oxidants help to oxidize minerals and contaminants in the water, killbacteria, reduce biofilm, and break down calcium buildup (inhibiting scaling). The dissolved oxidantscombine with water molecules to create hydrogen peroxide, a lasting biocide, though a small amount ofbiocide was still added to the system that was demonstrated. With this system, no additional standardcooling tower water treatment chemicals are typically needed, except that biocides such as bromide orother algicides may be used to control algae growth in the summer.The installation of the product is simple . The unit is mounted on the wall, a pipe with an air diffuser totreat the cooling tower water is routed from the device to the cooling tower basin, and no significantmodification of the current cooling tower water treatment system is required.Building 95 at the Denver Federal Center is a 163,206 ft2, two-story office/laboratory building that wasconstructed in 1999. The major tenant is the U.S. Department of Interior. Building 95 has two 250-tonDEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN Tiii

water-cooled centrifugal chillers that supply chilled water to the facility. The cooling tower is a 500-toninduced draft cooling tower, with two cooling tower cells and two-speed fan motors.The AWT technology was evaluated with a combination of on-site chiller plant energy measurements,cooling tower makeup water measurements, and outputs from the building automation system.Electrical energy for the chilled water plant and cooling tower makeup water was metered directlythrough GSA’s automated metering program, and 15-minute interval data were available from 2014 to2017. Outside air conditions, including dry bulb temperature, dew point temperature, wind speed, andprecipitation, were recorded on an hourly basis from the National Renewable Energy Laboratory’s SolarRadiation Research Laboratory and daily average values of average dry bulb temperature, minimum drybulb temperature, maximum dry bulb temperature, average dew point, average wind speed, and totaldaily precipitation were taken from Weather Underground for Denver, Colorado. The condenser watersupply and return temperatures for the main condenser loop were trended via the building automationsystem at a recording interval of 15 minutes for 2016–2017. Condenser pump #1 and #2 speeds weretrended via the building automation system at a recording interval of 15 minutes for 2016–2017.The AWT technology was installed in December 2014, and calendar year 2014 was used as the baselineyear for the study. The AWT contractor analyzed the condition of the condenser tubes in early 2015 andnoted that the condenser tubes were partially fouled with scale buildup. In addition, the 2017 electricalmeter data and condenser water meter data had the fewest data drop outs, so 2017 was used as thepost retrofit savings case. The National Renewable Energy Laboratory did not install any secondary dataacquisition systems and did not perform the same level of measurement and verification as other GSAProving Ground projects because this project was financed by GSA Region 8 and not the national GSAProving Ground. In addition, the existing metering system data and building automation system datawere used to characterize the cooling tower makeup water savings for both the baseline period andpost-retrofit period. A listing of quantitative and qualitative performance objectives and measurementand verification results are provided in Table 1.Table 1: Performance ObjectivesQuantitativeObjectivesSuccess CriteriaMetrics & DataWater Savings 10% reduction in coolingtower water makeup(gal/kWh)- Cooling tower makeup water- Chiller plant energy usage- Outside air temperature, dewpoint, wind speed, andprecipitationReduction inChemical Costs 90% reduction in annualchemical costs- Pre and post installationannual chemical costsWater ChemistryMeets or exceeds GSA coolingtower water chemistryrequirements- Pre and post installation waterchemistry reportsCost-EffectivenessEase of InstallationSimple payback (SPP); Savingsto Investment ratio (SIR)Less than 2-day installationtime- Payback 10 years; SIR 1.Labor hours to install technologyMeasurement andVerification ResultsMet: Annual waterreduction 22.7% to 29.7%Met: Elimination of allchemicals other thanbiocidesMet: Passed GSA waterchemistry requirementsfor all metrics other thanoxidation reductionpotentialMet: SPP of 6.2 yrs.; SIR of2.4Met: Less than 1 day toinstallDEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN Tiv

The estimated annual cooling tower makeup water savings is 527,791 gallons/year, with a range ofestimated savings from 433,288 gallons/year to 622,307 gallons/year. The estimated total annualcooling tower makeup water savings is 26.3%, with a lower bound estimate of 22.7% and a higher boundestimate of 29.7%. The equipment costs for the two AWT processing units was 29,780, the installationcost was 2,970, for a total cost of 32,750 ( 65.5/ton). The 12-month service agreement was 3,300( 275 per month). The annual water savings, cost savings, and economics for the system are provided inTable 2.Table 2: Annual Cost Savings and e w/Local Sewer Water Rate( 7.14/kGal.)Differencew/ GSA Avg.Water Rate 16.76/kGal.N/A 32,750 32,750 22,487 65.50 65.50 44.97BaselineInstallation ( )Installation Cost ( /ton)Annual Maintenance 5,855/yr. 3,333/yr. 2,522/yr. 2,522/yr.Annual Water 27,791Annual Water Costs( /yr.) 14,303 10,535 3,768 8,846Annual Energy Costs ( /yr.) 0 1,041 1,041 578Simple PaybackYrs.6.22.1Savings-to-Investment RatioInteger value between 0 and 1002.47.2The new cooling tower operations and maintenance contract for the AWT saved the site 2,522 peryear, with a 50% reduction in man hours. The two AWT units had a combined power draw of 1.2 kW andoperated for 8,760 hrs./yr., for a total power consumption of 10,512 kWh/yr. and an estimated energycost of 1,137/yr. The annual water cost savings was 3,768 per year (using a combined water sewerrate of 7.14/kgal.) and the simple payback period is 6.2 years, with a savings-to-investment ratio of 2.4,using a 15 year project lifetime. Given that for future installations of this size, both GSA and the vendorhave confirmed that just one AWT processing unit would be needed, the installed cost for that case wasestimated to be 22,487, with an energy usage of 5,250 kWh/yr., at a cost of 578/yr. Using GSA’snational average combined water and sewer rate of 16.76/kgal., the annual water savings would havebeen 8,846/yr, with a simple payback of 2.1 years and a savings-to-investment ratio of 7.2.The installation requires only simple wall mounting and the injector hose is connected to the coolingtower basin. Thus, the total installation time of only a few hours was much less than the performancemetric requirement of less than 2 days.For 2017, the annual average cycle of concentration was 9.54 and all of the tower water chemistryvalues were within the GSA designated ranges. The operations and maintenance contractor servicing thefacility continued its service contract and, after an initial descaling period, no additional water treatmentchemicals were added to the system other than the bromine/chlorine biocides to prevent biologicalDEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN Tv

growth, significantly reducing the chemical usage of the tower and lowering the environmental impactof the chemicals being drained via the blow down cycle. As noted above, this also resulted in a 50%reduction in labor hours to service the cooling towers and a 2,522 operations and maintenance savingsper year.This AWT product was analyzed as a potential retrofit option for smaller building applications that maynot have full-time or on-site cooling tower operations and maintenance contractors. This product isunique in that it can be used without additional monitoring aside from a low-cost service agreement.For future installations, Denver Federal Center staff have indicated that they would suggest leasing thetechnology as part of the service contract with the vendor instead of purchasing it, given that theinstallation is very quick and potential removal of the technology is not disruptive to the balance ofsystem.DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN Tvi

Table of ContentsEXECUTIVE SUMMARYIIII.1INTRODUCTIONA.WHAT WE STUDIED . 1B.WHY WE STUDIED IT . 2II.EVALUATION PLAN4A.EVALUATION DESIGN . 4B.TEST BED SITE . 4C.METHODOLOGY . 7III.DEMONSTRATION RESULTS11A.QUANTITATIVE RESULTS . 11B.COST-EFFECTIVENESS . 18C.QUALITATIVE RESULTS . 20IV.SUMMARY FINDINGS AND CONCLUSIONS21A.OVERALL TECHNOLOGY ASSESSMENT AT DEMONSTRATION FACILITY . 21B.LESSONS LEARNED AND BEST PRACTICES . 21C.DEPLOYMENT RECOMMENDATIONS . 21V.DEPLOYMENT GUIDANCE (GSA ONLY)27A.INSTALLATION AND COMMISSIONING. 27B.IMPACT ON FACILITY OPERATIONS . 27C.IT SECURITY AND CONTINUITY OF CONNECTIVITY . 27D.TECHNOLOGY MARKET READINESS. 27E.TECHNOLOGY SPECIFICATIONS . 27VI.APPENDICES28A.REFERENCES . 28B.GLOSSARY . 29C.MANUFACTURER CUT SHEET . 30DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN Tvii

I. IntroductionA. WHAT WE STUDIEDA cooling tower uses the evaporative cooling process to reject heat to the atmosphere from a watercooled chilled water plant. Cooling towers are commonly applied to water-cooled chilled water plants inlarge commercial buildings. The continuous evaporation of pure water from the condenser leavesbehind any natural mineral content the water carried (silica, calcium, magnesium, chloride). Thus, theremaining condenser water will have an ever-increasing concentration of impurities as more waterevaporates. These impurities eventually will precipitate out (because water can hold only so much),resulting in solid precipitate. This solid precipitate is commonly called scale and will collect on varioussurfaces it touches. Scale has a substantial detrimental effect on heat transfer surfaces; it lowers theefficiency of the heat transfer process, causing the chiller to use increasingly more energy over time toachieve the same level of cooling. In addition to scale, biofilms also have a significant impact on heattransfer efficiency. The high-water content of biofilms creates an insulating layer that inhibits energytransfer to a much greater degree than mineral scale alone (because of the high specific heat of water).Typical water treatment consists of injecting chemicals into the condenser water for the following threepurposes: Chemicals called “scale inhibitors” alter the natural ability of water so that it can hold a higherconcentration of minerals. Chemicals called “corrosion inhibitors” decrease corrosion in piping systems. Chemicals called “biocides” and “algicides” mitigate biological growth in the cooling tower,where warm water is exposed to air.In addition to the chemical treatments, a portion of the cooling tower water is typically drained off astower “blowdown” or “bleed-off.” This water volume is then replaced by fresh “makeup” water. Thisprocess lowers the chemical and mineral concentration of the remaining condenser water. It also lowersthe cycle of concentration (CoC) of the cooling tower and increases annual cooling tower water usage.GSA requires that cooling towers have a CoC of 2 or greater. A higher CoC will lower both blowdown andtotal water consumption.The Silver Bullet alternative water treatment (AWT) technology is a non-chemical-based cooling towerwater treatment technology. It is promoted as a simpler water treatment technology that can reducecooling tower blowdown by increasing the CoCs, which reduces monthly chemical costs, monthlyoperation and maintenance costs, and the amount of scale that collects on condenser water tubes andcooling towers.The product uses an advanced oxidation process. It pulls air from the surrounding environment, whichthen passes through patented sleeves that contain ultraviolet lamps and other proprietary componentsthat modify the air, creating negatively charged oxygen atoms. These diffuse into the water, forminghighly reactive hydroxyl and other radicals. The hydroxyl radicals and other oxidants help to oxidizeminerals and contaminants in the water, kill bacteria, reduce biofilm, and break down calcium buildupDEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T1

(inhibiting scaling). The dissolved oxidants combine with water molecules to create hydrogen peroxide,which acts as a lasting biocide, though a small amount of additional biocide is typically still added withthis system. With this system, no additional standard cooling tower water treatment chemicals need beused, except that biocides such as bromide or other algicides can be used to control algae growth in thesummer.The product is the size of a large electrical panel and can be retrofitted in less than a day. It is typicallyrented on a monthly basis at a cost that is comparable to traditional chemical treatments. A picture ofthe product is provided in Figure 1 (Silver Bullet n.d.-a).Figure 1: Non-Chemical-Based Cooling Tower Water Treatment TechnologyThe process uses an EPA recognized effective biocide via the advanced oxidation process and is easilyautomated and controlled. The vendor offers a smaller unit for cooling towers up to 400 tons or 1,200gallons per minute (gpm) and a larger unit for systems up to 2,000 tons or 6,000 gpm. The smaller unitsdraw 396 watts of power and the larger unit draws 720 watts of power while operating.B. WHY WE STUDIED ITCooling tower-related water consumption is one of the largest potable water loads within buildings inthe United States. Figure 2, a breakdown of water consumption in office buildings, shows that morethan 28% of building water use is associated with heating and cooling. This is by far the dominant wateruse case, owing largely to the evaporative cooling demands from either water-cooled cooling towers orevaporation-based air-conditioning systems.DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T2

Figure 2: Office Building Water End Uses (EPA n.d.)Cooling towers can be found in all states throughout the country, and this technology can save water inevery climate zone. Facilities located in hotter climates with a cooling season that lasts for more than 5–6 months per year, though, will use their cooling towers more and have greater cooling tower watersavings as a result.The Denver Federal Center is located in Colorado and GSA Region 8. In GSA Region 8, cooling towers areinstalled at thirty of the larger buildings in the region. Although the number of cooling towers in eachGSA region is unknown, it is expected that each region has numerous cooling towers that could benefitfrom reducing water consumption.DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T3

II. Evaluation PlanA. EVALUATION DESIGNThe primary focus of this evaluation was measuring cooling tower makeup water usage pre- and postinstallation of the AWT. In addition, annual reductions in cooling tower chemical costs, monthly waterchemistry reports, ease of installation, and overall cost effectiveness were evaluated.Table 3 lists the performance objectives, success criteria, and metrics used to evaluate each of theobjectives.Table 3: Performance ObjectivesQuantitative ObjectivesSuccess CriteriaWater Savings 10% reduction in cooling towerwater makeupReduction in ChemicalCostsWater ChemistryCost-EffectivenessQualitative ObjectivesEase of Installation 90% reduction in annual chemicalcostsMeets or exceeds GSA cooling towerwater chemistry requirementsSimple payback; Savings toinvestment ratio (SIR)Success CriteriaLess than 2-day installation timeMetrics & Data- Cooling tower makeup water- Chiller plant energy usage- Outside air temperature, dew point,wind speed, and precipitation- Pre and post installation annualchemical costs- Pre and post installation waterchemistry reports- Payback 10 years; SIR 1Metrics & DataLabor hours to install technologyB. TEST BED SITEBuilding 95 at the Denver Federal Center is a 163,206 ft2, two-story office/laboratory building that wasconstructed in 1999. The major tenant is the U.S. Department of Interior. Building 95 currently housesthe National Water Quality Laboratory — the flagship analytical facility for the U.S. Geological Survey ofthe U.S. Department of the Interior (Figure 3).DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T4

Figure 3: Building 95 at the Denver Federal CenterBuilding 95 has two 250-ton water-cooled centrifugal chillers that supply chilled water to the facility.The chiller is rated at 0.5 kW/ton and has a rated evaporator flow rate of 350 gpm and a ratedcondenser flow rate of 750 gpm. There are two 20 hp centrifugal condenser water pumps, rated at 750gpm at 75 ft of head, serving the two chillers. The cooling tower is an induced draft cooling tower, withtwo cooling tower cells and two-speed fan motors (Figure 4).DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T5

Figure 4: Building 95 Induced Draft Cooling TowerFigure 5 provides a picture of the AWT treatment system installed in building 95.Figure 5: Building 95 Alternative Water Treatment SystemDEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T6

C. METHODOLOGYQuantitative Study DesignThe AWT technology was evaluated through a combination of on-site chiller plant energymeasurements, cooling tower makeup water measurements, and measurements taken from theBuilding Automation System (BAS). A high-level description of the monitoring points is provided below:On-Site SubmeteringElectrical Energy — Building 95 has an automated submeter for the chilled water plant that records 15-minute electricity usage for the entire chilled water plant, including chillers, coolingtower fans, condenser water pumps, and chiller primary and secondary pumps.Cooling Tower Water — The cooling tower makeup water is metered directly by an on-site water meter and provides 15-minute interval cooling tower water usage data dating back to2013.Outside Air Data Outside Air Conditions — Outside air conditions, including dry bulb temperature, dew pointtemperature, wind speed, and precipitation, were analyzed on an hourly basis by the NationalRenewable Energy Laboratory’s (NREL’s) Solar Radiation Research Laboratory and dailyaverage values of average dry bulb temperature, minimum dry bulb temperature, maximumdry bulb temperature, average dew point, average wind speed, and total daily precipitationwere recorded from Weather Underground for Denver, Colorado (NREL n.d., WeatherUnderground 2013).Building Automation System Trend Logs Condenser Supply and Return — The condenser water supply and return temperature for themain condenser loop was trended via the BAS at a recording interval of 15 minutes for 2016through 2017. Condenser Pump Speed — The condenser pump #1 and #2 speeds were trended via the BAS at arecording interval of 15 minutes for 2016 through 2017.The condenser cooling load was calculated via the condenser pump start/stop, pump speed, andcondenser supply and return temperature difference from the BAS for 2016. NREL did not install anysecondary data acquisition systems and did not perform the same level of measurement and verification(M&V) as on other GSA GPG projects because this project was financed by GSA Region 8 and notthe national GSA Proving Ground. For this project, only the existing metering system data and BASdata were used to characterize the cooling tower makeup water savings (for both the baseline periodand post retrofit period). A list of monitoring points, instruments, and instrument accuracy is provided inTable 4.DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T7

Table 4: Monitoring Points and InstrumentationMonitoring PointInstrumentDescriptionLocationChiller PlantEnergyExisting automatedelectrical submeterBuilding 95chiller plant /- 0.5%Cooling TowerMakeup WaterExisting automatedwater submeterBuilding 95cooling towermakeup /- 0.4%Condenser WaterSupply and ReturnTemperatureBAS temperaturesensorBuilding 95condenser loop /- 10%Condenser PumpSpeedBAS trend pointOutside AirTemperatureTemperature sensorOutside Air DewPointCombination ofrelative humidity andtemperature sensorWind SpeedWind vanePrecipitationRain gaugeBuilding 95condenser pump#1 and #2Measurement &InstrumentationData Center(NREL MIDC)(NREL n.d.-b);WeatherUndergroundNREL MIDC;WeatherUndergroundNREL MIDC;WeatherUndergroundNREL MIDC;WeatherUndergroundInstrument Accuracy /- 0% /- 2%; /- 5% /- 2%; /- 5% /- 2%; /- 5% /- 2%; /- 5%Study DesignOn-site building operators and cooling tower maintenance technicians logged water chemistry andcondenser tube fouling pre and post installation. GSA has developed the water chemistry standardsgiven in Table 5 as a guideline to determine an acceptable blowdown water quality for a given AWT, andthey were adopted for this project location. Operations staff and AWT vendors performed monthlymonitoring of these parameters to characterize the performance of the system. It should be noted thatadherence to these ranges is not the only indicator of an AWT’s success. The operation of each AWT isunique and, due to the materials used in its design, may result in water quality that falls outside theranges defined in the project specifications. In the AWT selection process, a site should be sure toconsider site-specific water quality constraints, whether due to influent potable water or dischargepermit limitations.DEMO NS TRA TION A ND EVA L UA TION OF A N ADVA NCED OX IDA TION TE CH NOL OGY FOR COO LI NGTOWER WATER TR EATMEN T8

Table 5: Water Quality Criteria (as defined by GSA)TestT alkalinity (parts per million [ppm])Acceptable Ranges100–1000pH7.3–9.0Chloride (ppm)10–500CyclesTotal Hardness (ppm) 2500–1500Phosphate (ppm)43,327Conductivity (millimhos [mmHos]) 2400Bacteria Count (cfu) 80,000Water AppearanceClearIron (ppm) 4Calcium Hardness (ppm) 500Magnesium Hardness (ppm) 100Chlorides (ppm) 250Salt (ppm) 410Sulfates (ppm) 250Silica (ppm) 150Oxidation Reduction Potential(millivolts [mV])90-day Copper Coupon (mils peryear [mpy]) 300 0.290-day Mild Steel Coupon (mpy) 390-day Galvanized Steel (mpy) 490-day Stainless Steel (mpy) 0.1Data AnalysisThe chiller plant energy and cooling tower makeup water 15-minute totalizing meter readings wereavailable for 2014 through 2017. The BAS trend logs were o

treat the cooling tower water is routed from the device to the cooling tower basin, and no significant modification of the current cooling tower water treatment system is required. Building 95 at the Denver Federal Center is a 163,206 ft2, two-story