Water quality in drip irrigation附翻译.docx

Water quality in drip irrigation附翻译.docx

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Waterqualityindripirrigation附翻译

附录英文翻译

Waterqualityindrip/trickleirrigation:

Areview

ES.Nakayama1andD.A.Bucks2

1USWaterConservationLaboratory,4331EastBroadway,Phoenix,AZ85040,USA

2USDepartmentofAgriculture,AgriculturalResearchService,NationalProgramStaff,Beltsville,MD20705,USA

Summary.：

Theintensivetreatmentofirrigationwaterre-quiredfortheproperoperationofdripirrigationsystemsispresentlyanacceptedpractice.Tocontrolemitterclog-ging,weneedtoknowthebasiccausesofclogging.Themajorcloggingfactorshavebeenidentifiedandcontrolmeasuresdevelopedtopreventemittermalfunction.Allemittercloggingproblems,however,havenotbeensolvedprimarilybecauseofcost.Themainapproachtocontrolcloggingisproperwatertreatment.Thetypeoftreatmentisbasedonthequalityoftheirrigationwater,whichcanbeclassifiedintermsofitsphysical,chemicalandbiologicalcomposition.Thecausesofemittercloggingandpossiblewatertreatmentandpreventivemeasurestomaintainreliableoperationarereviewed。

Waterqualityandemitterclogging

Dripirrigationinthemid-1960'sthroughmid-1970'swasconsideredanemergingtechnologywithitsapplicationlimitedonlytohigh-priced,specialtycrops.Todayitisusedonawidevarietyofcrops,eventhosethatwereinitiallyconsideredunprofitableformanagementunderdripirrigation.

Throughcarefulnurturing,dripirrigationhasgrownintoastableandeconomicallysignificantpartofthefarmingcommunitywhichhasalsohadgreatimpactontheirrigationandassociatedindustries.Initsinfancysomedifficultandseeminglyunsolvableproblemswereencounteredinoperatingdrip/tricklesystemsparticularlythoserelatedtothecloggingofemitters.Alsoduringthisperiod,numerousinventorsandentrepreneurssoldvarioustypesof"non-clogging"or"self-cleaning"emitterswhichwerepromisedtosolvethemostseriousproblemofemitterplugging,butunfortunatelydidnotadequatelydoso.Thecloggingproblem,ifnotproperlysolved,wouldhaveresultedinthecompleterejectionorsevererestrictionofapromising,efficientmethodofirrigationandwaterconservation.Workonimprovingdripsystemoperationswentalongtwodifferentdirections,independent,butcloselyintouchwithoneanother.Onegroupconcentratedonimprovingthehydraulicoperationoftheemitters;theotherfocusedonstudyingthecloggingprocessandfromsuchknowledgedevelopingproceduresforalleviatingthecloggingproblem.Themainconclusiondrawnfromthelattertypeofstudiesisthatcloggingiscloselyrelatedtothequalityofwaterusedinthedripsystem,e.g.Bucksetal.（1977）,FordandTucker（1975）,Gilbertetal.（1981）,McElhoeandHilton（1974）,Nakayamaetal.（1977）,Pellegetal.（1974）.Researchcontinuestobereportedonirrigationwaterquality,treatment,anduniformityofapplication（Hilletal.1989;KinoshitaandBui1988;Pad-makumariandSivanappan1985）.Waterdivertedfromothertraditionalirrigationusageispresentlythemajorsourcefordripirrigation,butthissituationisbeginningtochangetowarduseofwastewaterfromcitiesandindustries.Thesetypesofwaterhavedifferentwaterquality,andconsequently,differentcloggingparametersareinvolvedsothatdifferentwatertreatmentproceduresmustbeused（Adin1987;AdinandElimelech1989;Chandra-kanthetal.1988;Gamble1986）.

Causesofemitterclogging

Forsurface-placeddripsystems,inspectionoftheflowbehaviorcanreadilydeterminewhenanemitterisoperatingproperly.However,externalexaminationalonecannotgiveanaccurateevaluationofthecauseorcausesofemitterclogging.Mostcloggingstartsinsidetheemitteranditmaystartveryslowlyandprogressslowlyoroccuralmostovernight.Partialcloggingisjustasbadasacompletecloggingbecausetheybothreduceapplicationuniformityandalterthehydraulicsoftheentiresystem.Todeterminetheexactnatureofthecloggingprocess,carefulphysical,chemical,andbiologicalexaminationoftheemittersandsupplylinesmustbemade.Inaddition,Thecompositionofthewaterusedinthesystemmustbedetermined.Becauseofthevarietyoffactorsinvolved,amultidisiplinaryapproachmustbetaken.Tofocusfurtheronthemultiplecausesofemitterclogging,atablewasdeveloped,whichincorporatesalltheinformationavailableatthattimeonthefactorscontributingtoclogging（Table1）.

Table1.Physical,chemicalandbiologicalfactorsinvolvedinemitterclogging（Bucksetal.1979）

Theresiduesforalargenumberofemittersandtubingwereexaminedchemicallyandmicroscopicallytoascertainthecomponentsofthecloggingmaterial.Informationonthecompositionsforvariouswatersourcesandtherelatedcloggingproblemsattherespectivesiteswereevaluated.Thecausesofcloggingvariedfromlocationtolocationsothateachsitewouldrequireadifferenttypeofwatertreatmenttopreventemitterclogging.Carbonatetypematerialswereprominentinsamplesfromthesouth-westernUnitedStates,whereasthemicrobialironclog-gingsubstanceswereabundantinthesamplestakeninthesoutheasternregion.Theprecedingfactors,however,arenotisolatedtoaspecificregion;instead,theyhavebeenobservedwithinthesameareaand,ofcourse,worldwide.Suspendedparticleshavebeenblamedformostemittermalfunction,buttheymayparticipateonlyindirectlyinthecloggingprocess.Frequently,thesmall,suspendedparticlesarecaughtbythefilamentandslimeby-productsofbacteriaandincreaseinsizetocauseemitterplugging.Thus,thecontrolofmicroorganismswouldhelpgreatlyinalleviatingemitterplugging.

Asurprisingobservationduringourinvestigationsondeterminingthecausesofemittercloggingwasthepresenceoflargequantitiesofmicroscopictosand-sizeplasticmaterialsobstructionemitteropenings.Theplasticcuttingsoriginatefromthesawingofthepipesduringtheinstallation,modificationorrepairofthedripsystem.Thisproblemcanbereadilycorrectedbycuttingthepipeortubingwithspeciallydesignedcuttersthatdonotformplasticparticles.Whensawingisnecessary,cleaningandflushingoftherepairedsectionsbeforetheyarereconnectedintotheconveyancesystemcanreduceplugging.Otherunusualobstructionswerethepresenceofoilandgreaseparticlesfromleakageofbearingsealsofwellandboosterpumpsthatareconnecteddirectlyintothedripsystem.Theobvioussolutioninthiscaseisthepropermaintenanceofthelubricantseals.Also,thesteelcasingofwellswasobservedtobethesourceofdissolvediron,whichisformedbyiron-reducingbacteria.Emittercloggingpreventioninsuchinstanceinvolvesthecontrolofthebacterialcontaminationortheuseofplasticinsteadofsteelcasing.

Abriefcommentshouldbemadeonthepresenceofsnailsinthedriplines.Theadultsnailscanbereadilyremovedfromthewaterbysimplefiltration.However,theireggsorlarvaecanpassthroughfiltersandeventuallymaturetotheadultformintheirrigationlineandcauserestrictedwaterflowintheemittersandlarger-sizedtubing.Otherorganismsthatcanpassthefiltersandundergosimilarmetamorphismorincreaseinpopulationorsizewouldalsocreatecloggingproblems.

Rootintrusionintoemitteropeningsandtubingthatrestrictwaterflowhasbeenobservedforsometypesofburiedtubing（Bui1988;KinoshitaandBui1988）.Emitterplugginginthiscaseisnotcausedbyirrigationwaterquality.

Waterqualityevaluationandclassification

Basedonthefindingsonemittercloggingandexperiencegainedincontrollingit,investigatorshavederivedaclassificationschemethatincludedthemajorfactorsinvolvedinemitterclogging.Thisisrelatedtoirrigationwatercomposition（Table2）.Suchaclassificationcanbeusedasaguideforidentifyingpotentialclogginghazardaswellasforselectinganddesigningwatertreatmentsystems.Littlechangeintheclassificationschemehasbeenmadesinceitsproposalintheearly1980's.

Exceptpossiblyformicrobialpopulationanalysis,measurementsofsuspendedloadandchemicalcompositioncanbemadebytheoperatorormostagriculturalservicelaboratories.Theeffectoffertilizerorotherchemicalsontheirrigationwaterthatmaycreatecloggingproblemscanbetestedbytheoperatorbytreatingthewaterwiththeadditive（GilbertandFord1986）.Testscanbeperformedinthelaboratoryoroffice,independentofthedripsystem,sothatthesystemwillnotbeadverselyaffectedifanynegativeresultsareobtained.AnyfertilizerorchemicaladditivethatincreasesthepH（alkalinity）ofthewatertothepointwherecarbonate,phosphateorhydroxidecanprecipitateshouldbeavoided.

Table2.Waterqualityclassificationrelativetoitspotentialfordripemitterclogging（Bucksetal.1979）

Rolstonetal.（1986）developedcriteriaforfertilizerapplicationindripsystems.Intheirpresentation,theyconsiderthesolubilityofthefertilizerandtheinteractionsofthefertilizerwiththedissolvecomponentsintheirrigationwater.Sincethen,acidifiedformsofnitrogenandphosphorushavebecomeavailable（urea-sulfateandurea-phosphate）,whichhavelesstendencytocauseprecipitationproblemsthanearlierfertilizerformulations（MikkelsenandJarrell1987）.

Waterswithhighconcentrationsofsulfideanionscancauseironprecipitation.Ironandmanganesesulfidesareveryinsolubleeveninacidsolutions.Thedissolvedsulfideanioncanalsoreactwithactivechlorinewhenthewaterischlorinatedsothattheeffectivenessofthechlorinationisreduced.Thus,thechlorinationrequirementofsuchwaterishigherthanthatofthetypicalnon-sulfideirri