CASESTUDY:CLEAN-FLOinversionoxygenationreverseseutrophication-improvesrawdrinkingwater

TheChallenge

ToaVacadamwasbuiltin1972tocreatea247acrerawdrinkingwaterreservoirinPuertoRico.Themaximumdepthisabout174feet.Theintaketowerforthewatertreatmentplanthas6intakegates,whichareeachabout30feetapart.Whenbuilt,ithadalifeexpectancyof300years;howeverby2009itwashighlyeutrophicandfishkillswerecommon.Theplantwasonlyabletousewaterfromthetop2gateswithoutsignificantlyincreasingtreatmentcosts.Thiscreatedasignificantproblemduringthedryseasonwhenreservoirlevelstypicallydropbelowthefirst2gates.

Ingeneralterms,reservoirshavelimitedverticalmixing,andwhencombinedwithahighresidencetimeandnutrientslikenitrogenandphosphorous,bothbluegreenalgaeandweedsfindtheperfectenvironmenttodominate.BlueGreenalgaehasnonaturalpredatorsandcanmoveupanddownthewatercolumn,thistogetherwiththeirabilitytoproduceenergythroughphotosynthesisprovidesthemwithanimportantcompetitiveadvantageoverotheralgaespecies.

Thetreatmentofrawwatercomingfromaeutrophicreservoirisarealchallenge.Oxygendepletedzonesatthebottomofthereservoircausethemigrationofmetalslikemanganeseandironandnuisancegaseslikehydrogensulfideandammoniatothewatercolumn.Onceatthedrinkingwaterplant,thiswaterrequiresanincreaseofchlorineandlimedosing.Thisleadstoanincreaseindisinfectionbyproductswhicharecarcinogenic.

TheSolution

CLEAN-FLOdesignedalaminarflowoxygenationsystemforthereservoirandatreatmentprogramforbio-augmentation.Thesystemwasinstalledin2012.Thebio-augmentationproductswereaddedapproximately4monthslater.Oursystemconsistedof14diffusersand35,000feetofairline.

Asamplingprogramwasestablishedeverytwoweeksinordertocloselymonitortherestorationprocess.Waterqualityparameterswereanalyzedatdiffusersthree(3),nine(9)andfourteen(14),atthreedifferentdepths(surface,halfdepthandthreefootfrombottom)including:dissolvedoxygen,oxidationreductionpotential,hydrogensulfide,nitrogen,phosphate,chlorophylla,andmanganese.Duringthestartupofthediffusersaremotemonitoringbuoywasinstalledandoperatedinordertoensurethattheemissionofhydrogensulfidegaswasperformedinacontrolledway.

Duringthefirstyearthewaterleveldroppedover70feetduetodrought.Thediffusersaremoreefficientwithdepth,sothereductionindepthsignificantlyaffectedtherateofoxygenationoftheentirewatercolumn.Asthedepthincreased,thepaceofrestorationimproved.

TheResults

ThebenefitsofrestoringToaVacareservoirareseveralandverifiable:•Treatmentplantcostreduction(25-35%)•Reductionofsludgeproduction(35-40%)

•Bettertasteandcolorofdrinkingwater(noyellowwater)•Reductionofdisinfectionbyproducts(TTHM)•Reducedimpactofwaterscarcity(rationing)•Increasedbiodiversity•Nofishkills,increasedfishcatching•ImprovedwaterinfrastructureforasustainableeconomicdevelopmentThese3graphsshowthereductionintotalphosphorus,totalnitrogen,andmanganeseatthebottomofthereservoiraftertheaerationsystemwasstarted.

Sincethesystemwasstarted,rawwaterqualityismoreconsistentwhichmakesthetreatmentplantmoreefficient.Customersareexpressingtheirsatisfactionforthebettertasteandodorofthewateratthetap.

CASESTUDY:Inversionoxygenationandbioaugmentationquicklyreducesorganicsediments

TheChallenge

LakeApopkaisa30,888acrehyper-eutrophiclakelocatedincentralFlorida.Onceknownforfantasticfishing,thelakehad28fishingcampslocatedaroundit.Decadesoffertilizerandchemicaluseinadjoiningparcelshavecontributedexcessivenutrientinputsthathavedevastatedtheaquaticecosystemandhavetransitionedthelakefromaclearmacrophyte-dominatedsystemtoaturbidphytoplankton-dominatedsystem.Largequantitiesoforganicsedimenthaveaccumulatedthroughoutthelakebottom,destroyingfishingandultimatelyendingtheoperationofallthefishingcamps.

TheSolution

TheStateofFloridacontractedourdistributorAlliedGroupforimplementingourinversionoxygenationandbio-augmentationina250acrepilotarea.ThesystemwasinstalledinAugust2015.Priortoinstallation,comprehensivebaselinewaterandsedimentsamplingwasundertakeninMay2015,andthenfollowedupwithmonthlysamplingoncethesystemwasstarted.InDecember2015,afteronly4monthsofoperation,thedatawasgatheredandanalyzedbyanindependentconsultanttodetermineifprogresswasbeingmade.

TheResults

Thereisnoseparatingbarrierbetweenthepilotareaandtherestofthelake,soconstantmixingoccurs.Evenwiththismixing,theresultsshoweda12.5%decreaseinbluegreenalgae,increasedwatercolumndepthandsignificantlyreducedwatercolumnammonia,sedimentphosphorousandorganicmatter.Thefollowingphotosshowthewaterbehindaboatbeforethesystemwasinstalledand4monthslater.

ThecontourmapsshownbelowrepresenttheincreaseinwaterdepththathasoccurredbetweenMayandDecember.Youwillseeanincreaseindepthwherethemuckhasbeenconsumedbythemicrobes.Eachlineinthesescansrepresentsanincreaseofonefootindepthfromthesurfaceofthelakewiththedarkbluebeingthedeepestpointsinthetreatmentarea.Thescaleattherightshowsthefeetdepthassociatedwitheachcolor.InDecember,weseesomeareasthatarefivefeetordeeperformingaswellasexpansionofthe2,3and4footdepths.

Themapsbelowshowthechangesfromred(densevegetationgrowth)toblue(novegetationgrowth)after4months.Additionallythetablebelowthemapsquantifiesthechangesinaquaticvegetationbio-volume.Therehasbeenasubstantialreductioninthehighestpercentcovercategories(60-80%)fromMaytoDecemberof2015.Thisisduetotheabilityofthelaminarflowaerationsystemtoaffectthesedimentporewaterchemistryanddrivethedenitrificationprocesswhichlimitssedimentnutrients(suchasammonia)tomanyrootedmacrophytes

%AquaticPlantBio-Volume

May2015 December2015 NetLossorGain

0%-5% 26.09% 85.93% 59.84%5%-20% 8.69% 10.87% 2.18%20%-40% 12.64% 1.29% (11.35%)40%-60% 17.76% 0.99% (16.77%)60%-80% 19.34% 0.55% (18.79%)>80% 15.48% 0.37% (15.11%)

Overalltheprojecthasbeenatremendoussuccesstodate.Theamountofvisualfishactivityinthetreatmenthasincreasedsubstantially,anditwillonlygetbetterwithmoretime.

HereisanaerialphotoofLakeApopkashowingthediffuserboilsonthesurfaceofthewater.