Energy Use Of Recycling Water Aquaculture Systems For Ornamental Fish Production

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Title:
Energy Use Of Recycling Water Aquaculture Systems For Ornamental Fish Production
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Bucklin, R.A.
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University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
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Gainesville, Fla.

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Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
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"Circular 1095"

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Circular1095 TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/JohnT.Woeste,Dean May1993EnergyUseofRecyclingWaterAquacultureSystemsfor OrnamentalFishProduction1 R.A.Bucklin,C.D.Baird,C.A.WatsonandF.A.Chapman2MostofFlorida'sornamentalfishproduction takesplaceinoutdoorponds,whereproduction successisoftensubjecttosuchnaturaloccurrencesas winterweather,thepresenceofaquaticweeds,and predationbybirdsandotheranimals.Mostfacilities alsousetanksforholding,breeding,andproducing certainfishspecies.Energyconsumptionisgreatest forwaterpumpingandheatingandcanbecomea majorbusinessexpense,especiallyduringthewinter andspring. Increasedwaterconsumptionisalsobecominga criticalprobleminFlorida,asmoreandmorepeople competeforthesameresource.Pondproduction requiresnotonlyavailablewaterbutalsoland suitableforfishponddevelopment.Landvaluesand regulationscontrollingdevelopmentcontinueto eliminatemanypotentialpondproductionsites,a situationthatthreatenstolimitexpansionofthe ornamentalfishproductionindustryinFlorida. Onealternativeisarecirculatingaquaculture system,whichremovessomeoftheinefficiencies inherentinproductionorholdingsystems.Water reusereducespumpingcostsandretainsenergy normallyusedtoheatwater.Inaddition,itenables productiontooccurinacontrolledenvironment wherelossestopredatorsandseasonaldroughtdo notinfluenceproductionplans.Finally,itpermitsa reductioninwaterconsumptionandtheproductionof largenumbersoffishinasmallarea. Thispublicationdescribesthecomponentsofa recirculatingwatersystemthatcanbeusedfor holdingand/orproductionofornamentalfish.Italso explainshowsuchasystemcanbedesignedtobe moreenergyefficientthanconventionalsystems. Recirculatingsystemsmaynotbeapplicabletoall situations,sincetheyrequireahighlevelof managementcapabilityandalargeinitialcapital investment.Certainspeciesandvarietiesof ornamentalfishmaynotreproduceordevelopinan indoorsystem,andwaterqualityanddisease managementhavehistoricallycausedproblemsin recirculatingsystems.Thealternativeofferedinthis publicationcansaveenergyandreducewater consumptioninmanysituations,especiallyinholding facilities.Thisisnottosuggestthatpondproduction ofornamentalfishisnotaviableoption.Information regardingtheenergyrequiredforconventional ornamentalfishproduction,especiallyinopenponds, isextremelylimited.Also,sinceproduction techniquesvarywithintheindustry,itisdifficultto generalizeaboutenergyrequirements.Nevertheless, thedataandexamplesprovidedinthispublication willservetodemonstratehowmoderntechnologies canbeemployedtoreducethecostsofornamental fishproduction. 1.ThisdocumentwaspublishedMay1993asCircular1095,aseriesoftheFloridaEnergyExtensionService,FloridaCooperativeExtension Service,InstituteofFoodandAgriculturalSciences,UniversityofFlorida. 2.R.A.Bucklin,AssociateProfessor,andC.D.Baird,Professor,AgriculturalEngineering;C.A.Watson,AquacultureExtensionAgentII, HillsboroughCounty,Seffner;andF.A.Chapman,AssistantProfessorofFisheriesandAquaculture,CooperativeExtensionService, InstituteofFoodandAgriculturalSciences,UniversityofFlorida,GainesvilleFL32611.

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EnergyUseofRecyclingWaterAquacultureSystems Page2COMPONENTSOF Figure1. Typicalwaterrecyclingaquacultureproductionsystem.AQUACULTURESYSTEMSThebasiccomponentsofatypical outdoorpondsystemareawater supply,awaterdistributionsystem,an aerationsystem,fishponds,anda waterdischargeorretentionsystem. Manypondsareequippedwithcovers toprovideprotectionfromcoldand predators.Mostbuildingsusedfor holdingorfishproductionareheated. Somefacilitiesdirectlyheatthewater inthesebuildings,employing conventionalgasorelectricresistance heaters. Althoughrecyclingsystemsmay varyinseveralrespects,atypical systemconsistsofawatersupply,a waterdistributionsystem,tanksfor holdingfish,afiltrationsystem,anaeration/degasser system,aheating/coolingsystem,andabuildingto housethesystem(seeFigure1).ENERGYSAVEDINPUMPINGMostoftheenergyusedinornamentalfish productionisappliedtopumpingandtemperature control.Thispublicationhighlightsthesetwo importantaspectsofornamentalfishproduction systems. Whileflowratesinarecirculatingwatersystem mayactuallybehigherthaninflow-throughsystems, thelowerpumpingheadsavesenergy.Inflowthroughsystems,waterispumpedfromwellsasdeep as500feet.Manywellsonfishfarmshavediameters of4-6inches,andpumpsoftenhave5-to10horsepowercapacities.Recirculatingsystems,onthe otherhand,maypumpaslittleas10feetofheadand canbeoperatedonaslittleas1/2horsepower.Ina recyclingsystem,theonlyheadlossesareelevation headlossesbetweenthetanksonthefloorand elevatedtanksandfrictionheadlossesinthepipes, fittings,andfilter. Electricenergyissoldbythekilowatthour(1 horsepower=0.746kilowatts).InFloridain1992,a typicalpriceforakilowatthourofelectricitywas $0.08.Operatinga5-to10-horsepowerpumpat75% efficiencycostsapproximately$10-$19perday,while operatinga1/2-horsepowerpumpcostsabout$1per day.Clearly,thelowerinitialandoperatingcostsof thesmallerpumpareamongthemajoradvantagesof recyclingsystems. Beforepumpsareselectedforarecyclingwater system,therequiredflowratemustbedetermined. Thisisbasedontheflowrateneededtomaintain waterqualityforagivenweightoffishandthe expectedheadrequirementsofthesystem.Themain limitingfactorsinrecyclingsystemsarenitrogenous wastes(e.g.,ammonia,nitrites,andnitrates)and oxygen.Theremustbesufficientflowthroughthe tankstoreplacewaterbeforeitbecomeshighin nitrogenouswastesorlowindissolvedoxygen. Nitrogenouswastes,producedinproportiontothe amountoffeedconsumedbythefishinthesystem, almostalwaysconstitutetheprimarylimitingfactor. Mostoftheenergythatprovidesflowinarecycling systemisusedtoovercomedifferencesinelevation betweenthesumpandthefishtanksandtoovercome frictionintheplumbing.Theenergythatprovides flowinoutdoorflow-throughsystemsisconsumed chieflyinpumpingwaterfromasourcesuchasa deepwellandinovercomingfrictioninthepipesand fittingsofthewaterdistributionsystem.Energyis alsousedinitiallytofillbothindoorwaterrecycling systemsandoutdoorponds.Whenviewedasa proportionofthetotalenergyusedperunitof production,theamountofenergyusedforfilling waterrecyclingsystemsissmall;however,theenergy usedtofilloutdoorpondscontributessignificantlyto productioncostsinsomesystems.

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EnergyUseofRecyclingWaterAquacultureSystems Page3ThevaluesinTable1arebasedonthefollowing Table1. Flowratesfortypicalwaterrecyclingsystems. Weightof fishin kilograms Weightof fishin pounds Flowratein litersper hour Flowrate gallons perminute 2,0004,40038,400 169 1,000 2,200 19,200 85 5001,1009,600 42 250 550 4,800 21assumptions: Thefishconsumeanamountoffeedequivalent to1%oftheirtotalbodyweighteveryday. Thefeedhasaproteincontentof35%. Thebiologicalfilterhasaremovalefficiencyof 35%. Alltheammoniaproducedbythemetabolizingof feedisexcretedin6hours. Thefisharefedfourtimesperday. ForthewaterrecyclingsystemsdescribedinTable 1,aflowrateof0.038gpmperpoundoffishis requiredtocontrolammonia.Inanaveragewater recyclingsystemhousedina20-by30-footstructure, with550poundsoffishandaflowrateof21gpm, approximately50feetof1-1/2-inchPVCpipewitha frictionheadlossof1.6feetwouldberequired. Assumingthereweretwelve90elbowsandfourgate valvesinthesystem,anadditional1.6feetofwater headlosswouldoccurintheelbowsandgatevalves. Atypicalelevationheadforasystemofthissizeis5 feet.Therefore,thetotalheadinplumbingwouldbe 8.2feetofwater.Assuminganadditional5.8feetof headlossinfilters,thetotalheadwouldbe14.0feet ofwater.Ifapumpwithanoperatingefficiencyof 50%wereused,a0.15-horsepower(i.e.,0.11-kilowatt) motorwouldberequiredtoproduceaflowof21gpm against14feetofwaterhead.Amotoroperated continuouslyatanefficiencyof75%wouldrequire 3.5kilowatthoursofenergyperday. Aflow-throughsystemhousedinasimilar structureandusingtanksofthesamesizewould requireacontinuousflowof21gpmfromadeep well.Astandardornamentalfishproductionsystem includesa150-footwelllocated50feetfromthe building.Thistypeofsystemrequiresapumpthat cansupplythesamequantityofwaterastherecycling systembutatamuchhigherhead.Theheadlosses forthesysteminclude150feetofelevationheadloss fromthewaterleveltothegroundsurfaceanda frictionlossof1.6feetofwaterinthe50feetofpipe betweenthewellandtheproductionstructure,in additiontofrictionlossesintheplumbingwithinthe structure.Atypicalflow-throughsystemwith550 poundsoffishandaflowof21gpm,housedina20by30-footstructure,wouldrequireapproximately25 feetof1-1/2-inchPVCpipe,withafrictionlossinthe pipeof0.8feetofwater.Assumingthereweresix90 elbowsandtwogatevalvesinthesystem,an additional1.6feetofwaterheadlosswouldoccurin theelbowsandgatevalves.Atypicalelevationhead fortanksinasystemofthissizeis5feet.Thetotal dynamicheadfortheflow-throughsystemwouldbe 158.2feetofwater.Apumpoperatingatan efficiencyof50%wouldrequire1.7horsepower(i.e., 1.25kilowatts)toproduceaflowof21gpmagainst 158.2feetofwaterhead.Ifthepumpwerepowered byanelectricmotoroperatedcontinuouslyat75% efficiency,itwoulduse40.1kilowatthoursofenergy perday. Inatypical550-poundsystem,36.6fewerkilowatt hoursofenergyperdayareconsumedbyusing recyclinginsteadofflow-throughsystems.The ornamentalfishindustryinFloridaiscomposedof 1,240acresofoutdoorpondswithanannual productionofapproximately2,280,000poundsoffish. Ifhalftheindustryusedindoorwaterrecycling productionsystemssimilartotheonedescribed,the energysavingswouldbe76,000kilowatthoursper day,or27,700,000kilowatthoursperyear.At$0.08 perkilowatthour,thiswouldresultinsavingsof $6,000perday,or$2,200,000peryearforthe industry. Itisdifficulttomakecomparisonsbetweenindoor recyclingsystemsandoutdoorpondsystemsbecause ofsystemvariations.Ingeneral,however,recycling systemshavethepotentialtoreducepumpingcosts, particularlyduringspringdroughtswhenwaterlevels mustbemaintained,andduringcoldperiodswhen waterispumpedtomaintainwatertemperatures. Energyusageforoutdoorpondsvariesconsiderably andisheavilyinfluencedbythedepthofwaterina system'swell.Whenwellwaterisavailableatadepth of70feetorless,orwhengroundwaterishighand evaporationlow,thedifferencebetweentheamount ofenergyconsumedinrecyclingsystemsandthat usedinpondsystemsisminimal.However,recycling

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EnergyUseofRecyclingWaterAquacultureSystems Page4systemshavepotentialadvantagesoverpondsystems whenwellwaterisavailableonlyatadepthgreater than70feetorwhenspaceislimited.Assumingan averageweightof1gramperfishandavolumeof 10,000fishperpond,a550-poundrecyclingsystem wouldhavethesamecapacityas24outdoorponds. Inaddition,atypical24-pondsystemoccupies2-3 acresoflandthatcouldbeusedmoreproductivelyfor otherpurposes.SELECTIONOFPUMPSAND PLUMBINGCOMPONENTSSizeandoutputmustbeconsideredwhen selectingpumps.Apumpmustbelargeenoughto deliverthedesiredquantityofwater,usually measuredinlitersperhouroringallonsperminute. Thepumpmustalsobeabletodeliverthisquantity ofwaterattheoperatingpressureortotalhead requiredbythesystem. Totalheadincludesthepressurerequiredatthe pipeoutlet(i.e.,pressurehead);thepressureneeded toraisewatertothedesiredelevation(elevation head);thepressurenecessarytoovercomefriction (frictionhead);andthepressurerequiredtoraise waterfromasumporotherwatersourcetothepump (suctionhead).Headcanbemeasuredeitherinfeet ofwaterorinpoundspersquareinch(psi)(psix2.31 =feetofwater). Apump'sefficiencyvarieswiththerateofoutput andthetotaldynamichead.Themanufacturer shouldprovideatableorgraphdescribingthe relationshipbetweenthesefactorsandpump efficiency.Theconsumermustmakesurethatthe pumpselectedoffersthedesiredoutputatthehighest pumpefficiency.Carefulpumpselectionenablesthe usertooperateasmallerpump(i.e.,onewithalower horsepower)thanisrequiredbymostwells. PVCpipeandfittingsarerecommendedfor recyclingwatersystems.TheadvantagesofPVCpipe arethatitisrelativelyinexpensiveandissubjectto lesspressuredropduetofrictionthanothertypesof pipe.Fittingsareamajorsourceoffrictionlossin pipingsystems.A90standardelbowexperiencesthe sameamountofpressuredropas32diametersof straightpipe.Therefore,whenthelayoutofapipe systemisbeingplanned,thenumberofelbowsand otherfittingsshouldbeminimized.Sincevalvesare anothersourceoffrictionloss,gatevalvesshould alwaysbeusedinsteadofglobevalves.Anopengate valvehasafrictionlossequivalentto7diametersof straightpipe,whereasanopenglobevalvehasa frictionlossequivalentto300diametersofstraight pipe.HEATINGSYSTEMSHeatingsystemsinconventionalfishproduction buildingsareofteninefficientbecausetheytypically heatairratherthanwater.Whenwaterisheated, eithergasorelectricwaterheatersareemployed, limitingefficiency.Inaddition,manyofthese buildingsuseflow-throughsystems,whichallow heatedwatertobedischargedandwasted.In outdoorpondsystems,plasticcoversmustbeusedor waterpumpedtoprotectthefishduringseverewinter weather.Usingconventionalmethodsoftenslowsor stopsproductionduringperiodsofpeakmarketvalue. Waterheatingiscostlyandrequiresagreatdeal ofenergy.Inflow-throughsystems,mostofthis energyislostwhenthewaterisdischarged.Recycling watersystemssaveasignificantamountofenergyand canprovideyear-roundproductioncapabilities.A recyclingsystemdirectlyheatswater;then,insteadof discardingthisexpensiveheatedwater,therecycling systemremovesthenitrogenouswastes,aeratesand degassesthewater,andreturnsthewatertothe tanks. Mostindoorsystemsrelyonelectricresistance heaterstoheatwater.Althoughtheseheatersare clean,convenienttouse,andaccessible,theyare expensivetooperate.Foroperationsrequiringheat formorethanafewdaysperyear,aheatingsystem thatburnsfueltoheatwaterismuchlesscostlyto operatethanoneemployingelectricresistance heaters.Forexample,assumingacostof$1per gallon,propaneburnedtogenerateheatprovides about80,000Btuofenergyperdollar.In comparison,ifelectricitycosts$0.08perkilowatthour,theamountofelectricityusedtopower resistanceheatingelementsprovidesonly43,000Btu perdollar. Heatpumpsofferanotheralternativeforwater heating.Theyallowtemperaturetobecontrolledat lowercoststhaneitherconventionalelectricorgaspoweredheatersandhavetheadditionaladvantageof beingabletocoolwaterduringthesummer.For specificinformationonselectingandinstallingaheat pumpinarecyclingsystem,UniversityofFlorida IFASCircular1096, HeatPumpforHeatingand CoolingWaterforAquaculturalProduction ,shouldbe consulted.

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EnergyUseofRecyclingWaterAquacultureSystems Page5HOUSINGAwaterrecyclingsystemmustbehousedina buildingtobeeffective.Awidearrayofstructures canbeusedforornamentalfishproduction. Greenhousestructuressuchasthoseusedbythe horticultureindustryforplantproductionare commonlyemployed.Greenhousestructuresare inexpensive,withmaterialcostsofapproximately$1 persquarefoot;however,theyhaveshortlifespans, areveryhotinthesummer,andaredifficultto insulateproperly,causinghighenergyusagefor heatingsystemsinthewinterandcoolingsystemsin thesummer.Economicalwoodormetalframe structures,withmaterialcostsaslowas$4-$6per squarefoot,offeranalternativetogreenhouse structures.Althoughconstructioncostsforwoodor metalframebuildingsaregreaterthanforgreenhouse structures,makingtheirinitialcosthigher,these structureshavemuchlongerlifespansthan greenhousestructures.Thebestgreenhouseplastics lastforonlythreeyearsinFlorida,whileawellconstructedwoodormetalframebuildinghasan expectedlifespanofmorethan20years.Woodor metalframebuildingsarealsobetterableto withstandthehighwindsthatoccurperiodicallyin Florida. Awoodormetalframestructurecaneasilybe insulated,reducingitsenergyusagetoalevelwell belowthatofagreenhousestructure.Theoverall thermalresistancetoheatflow,referredtoasthe "totalR,"indicatestheeffectivenessofabuilding's insulation.ThehigherthetotalRvalue,thelower theheatlossorgain.Adoublepolygreenhousehas atotalRvalueof1.4hr-ft2F/Btu.Aframe structurewithatotalRvalueof10-20hr-ft2F/Btu caneasilybeconstructed.Structureswithhighertotal Rvaluesreduceheatlossinthewinterandheatgain inthesummer,loweringenergyconsumption.CONCLUSIONSIndoorrecyclingsystemsofferseveraladvantages overconventionalornamentalfishproductionand holdingfacilities,includingincreasedenergy efficiency.Theuseofsuchmodernsystem componentsasheatpumpsandenergy-efficient buildingmaterialsallowsproducerstominimize energyexpenditures.Becauserecyclingsystemshave lowerwaterheadrequirementsthanoutdoorpond systems,equalorgreaterflowratescanbeachieved withlessenergy.Properdesign,includingaccurate calculationofheadrequirements,minimizationofthe numberoffittingsandvalvesusedinplumbing systems,andcarefulpumpselectiondiminishenergy needs.Additionalbenefitsofusingrecyclingsystems mayincludereductionsinwaterconsumptionperunit offishproduced,decreasesinlandusage,elimination oflossesduetopredation,andattainmentof year-roundproductioncapabilities. Recyclingsystemswillnotimmediatelyreplace pond-basedproductionfacilitiesinFlorida.Problems characteristicofcertainspecies,fishdiseases,water qualitymanagementissues,andeconomicfactorswill continuetofavortheuseofoutdoorpondsforsome timetocome.Nevertheless,recyclingsystemsoffer realsolutionstomanyproblemsencounteredin commercialornamentalfishproduction.Foremost amongthesesolutionsisasubstantialdecreasein energyusage.