THEME No.2

and ~3rIa~ft~ ‘ThJ. ~~

RECYCLING OF WASTEWATER ANDITS BY-PRODUCTS

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PRESENTATIONS

08h35 to 08h50

08h50 to 09h05

09h05 to 09h20

MANAGEMENT PRACTICESIN THE RECYCLING OF WASTEWATER:AGRICULTURAL AND INDUSTRIAL APPLICATIONS IN AFRICABy PierMANTOVAN! (DMWW/CGE)

RECYCLING OF TREATED WASTEWATER FOR GOLF COURSE

IRRIGATION, CASESTUDY: BEN SLIMANEBy A. FOUTLANE& B.A. YOUGOUBI (ONEP)

RECYCLING OF WASTEWATER AND ITS SUB-PRODUCTSBy CisséGUELADIO (EJER)

ThEME N°2

IBRARY ~RCP0 Box 93i90~2509 AD THE HAGUE

Tel; ÷3170 30 689 80Fax: ±317035 89964

BARCODE ~LO.

SANITATION: RE-USE OFWASTEWATER AND ITS

BY-PRODUCTS IN AFRICA

Contributors: GerieraledesEauxDurban Metro Water& Waste

PierMantovarii, GeneraledesEaux

Title: Issuesand Practicesin Wastewater Re-usePlanning:Agricultural and Industrial Applications in Africa

ABSTRACT

The fast developmentofurbanandsuburbancommunitiesis confrontedwith thefinite

natureof waterresourcesavailableto meetgrowing demands.In a trendnot limited

semi-aridzones,manyAfrican citiesalreadyexperienceseasonalor chronicwatersupply

deficits, while facingtherisk of overdraftingorpolluting existingresources.In such

communities,plannedwaterreclamationandreuseoffers theopportunityto createan

economicallyvaluablewaterresourceandto attenuatewaterdeficits. It alsofosters

environmentalconservationby limiting bothoverdraftingofwatersuppliesanddischarges

ofmunicipaleffluents.Waterreusecanthusbe animportantcomponentof anyintegrated

waterresourcesmanagementstrategy.

Waterreusefor nonpotableapplications,ornonpotablereuse,remainsto thisday the

dominantpractice.Potablereuseremainsan ill-perceived~,easilycontroversialpractice,restrictedto situationsofextremewaterdeficit. Commonnonpotablereuseapplications

includeagriculturalandlandscapeirrigation, industrialusesandenvironmentaluses.

Nonpotablereusefeaturesmoderatetreatmentcostsandis stronglyacceptedby users

becauseits sanitaryrisks arewell identified andcontrolled.Implementationof nonpotable

waterreusesystemsis facilitatedby theexistenceofregulatoryguidelinesaswell as

provenprocesses,suchasthoserecommendedfor irrigation by theWorld Health

Organisationin 1989.Nonpotablewaterreusealsofeaturesuniqueplanningchallenges

linked to theneedto distributeandsell thereclaimedwater.Challengesincludethe

identificationanddevelopmentof durablemarketsfor anoftenill-perceived“reclaimed

water” product;thefunding andrecoveryof ahefty dualdistributionsysteminvestment;the

competitionof subsidizeddrinking or irrigationwatersupplyalternatives;theset-upof a

third new serviceamidst existing watersupply andsewerageagencies,etc.

Recognizingthis, theWaterEnvironmentResearchFoundation(WERF)hascommissioned

anassessmentof nonpotablewaterreuseplanningandmanagementpractices.Suchstudy

encompassedsixty-five internationalnonpotablereuseprojectsto documentplanningand

managementapproachesfor agricultural,urbanor industrial reuseprojects,in bothadvanced

anddevelopingcountries.Findingsconfirm thatin additionto operationalperformance,

soundinstitutional arrangements,conservativecostandsalesestimatesandgoodproject

communicationsarethebasisfor project success.

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Following a reviewofthemain findingsandconclusionsof the study,two African casestudiesaredevelopedto illustratethediversity in technical,commercial,institutionalandfinancial approachesavailableto ensurelong-termsustainabilityof industrial andagriculturalreuseprojects:

The first dealswith a small agriculturalreusesystemin Tunisia. Implementedaspartofanationalwaterreuseprogram,theOuardanine(Monastir)project integratesawastewatertreatmentplant with 50ha of irrigatedlandandorchards.Benefittingfrom10 yearsofpreviousTunisianwaterreuseplanningandmanagementexperience,thissecondgenerationprojectstartedoperationsin 1995. It haseliminatedraw wastewaterdischargesto theenvironment,while sustainingstrongneweconomicactivity for afarmersassociation.

The secondcasestudy is radicallydifferentcontext:The SouthernWorksproject inDurban,SouthAfrica featureslarge-scalewaterreusefor industrialapplications.Implementedasaprivate concessionfor DurbanMetro WaterService,thisprojectwillprovide47 Mld of high quality processwaterto variousneighbouringplants, includingapapermanufacturer.Uponstart-upin 2000,thisprojectwill cuteffluentdischargesto theenvironmentandfree a significantvolumeof drinking waterfor humanconsumption.It will alsoafford largeprocesswatersupplysavingsto themanufacturers.Long-termsustainabilityoftheproject is promotedby innovativecontractingandrisk-sharingsolutionsthatapplybetweenthecommunity,the privatecontractor,anditsindustrialusers.

KEYWORDS

Waterreuse,nonpotable,planningandmanagement,Tunisia, SouthAfrica

1. INTRODUCTION

Urbanwaterdemandsareescalating,drivenby unprecedentedurbanandeconomicdevelopment.As withdrawalsfrom existingwatersuppliesapproachor exceedrenewalcapacity,thedevelopmentof newsuppliesis opposedby mountingcostsandenvironmentalconstraints.Concurrently,expandingurbanareasareunderpressureto reducetheenvironmentalandhealthimpactsof theirwastewaterdischarges.Many African citiesalreadyexperienceseasonalor chronicwatersupplydeficits,with mountingrisks ofoverdraftingandcontaminatingtheirsourcesof supply.

Oncelimited to siteswith extremearid-zonewaterdeficits, orwith exceptionnalystringenteffluentdisposalconstraints,reuseof reclaimedwastewateris an increasinglystrategicwatermanagementoption for growingcommunitiesworldwide.By creatinganewresourcewhile

3THEME N°2

reducingeffluent loads,waterreclamationandreuseis emergingasastrategiccomponentofintegratedurbanwatermanagement.Becauseofeasedpublic acceptance,well-controlledhealthrisks,andmorecomprehensiveregulatoryguidance,nonpotablereuseapplicationshavesofar beenwidely preferredoverpotableones.

While substantialtechnicalandoperationalexpertisehasthusbeendevelopedfor suchnonpotableapplicationsover thepast30 years(USEPA, 1992),utility plannersandmanagers arestill facedwith challenginginstitutional, legal,andliability issuesinherentto reclaimedwaterservice.Furthermore,becauseofuniquejurisdictionalandmarketconstraints,theeconomicbenefitsandfinancialperformanceofnonpotablereuseprojectsremaindifficultto assessandmaximize.Reclaimedwaterservicehasaptly beendescribedasa third utilityfunction(WERF, 1992),with distinct operationalandmanagementimperatives.Fortraditionalwatersupplyandsewerageagencies,its implementationrepresentsasignificantbusinessdiversification.Aroundtheworld, risks associatedwith suchplanningandmanagementuncertaintieshavebecomemorecrucial for projectimplementationandsustainabilitythanoptimizeddesignandoperations.Thepotentialoutcomeof inaccurateplanningassumptions,non-optimalserviceareas,non-competitivepricingor poorprojectcommunicationsis acommonfailure to achievereclaimedwaterdistributiongoals,therebyfalling shortofenvironmentalandfinancial objectives.

2. AN OVERVIEW OF NONPOTABLE REUSE

Figure1 illustratestheconceptsandtypical applicationsof waterreuse.Nonpotablereuseisdefinedasthebeneficialuseofreclaimedmunicipal wastewatereffluent, for applicationsthatdo not requirepotablequality.

Rankedin orderof decreasingconsumedvolumes,theseincludeagriculturalandlandscapeirrigation, industrialuses(cooling,processingandwashing)andenvironmentaluses(aquiferrecharge,pondandstreamrestoration).Municipal,commercialiind residentialuses

Figure1: Nonpotablewaterreuseconcepts& applications

4THEME N°2

mayalsoincludetoilet flushing, fire protection,gardenwatering,andcreationofornamentalorrecreationalwaterbodies.Rechargeofreclaimedwaterinto adrinking wateraquifer,withinthecapturezoneof watersupplywells wouldrankasindirectpotablereuse.

Inherentadvantagesofnonpotablewaterreusearethat it allowsto:

- servevariousnonpotabledemands,- conservefreshwaterresourcesfor higherquality usessuchaspotablesupply,- provide an alternativeto effluent dischargesto theenvironment.

Reclaimedwateris furthermoreavailablenearurbancentres,andrepresentsapracticallydrought-proofresource.As long astheyavoid ingestionby humans,well-operatednonpotablereusesystemsarealsovery safe,with no documentedcaseofpublic healthimpactin theUSA.

Besidesusagerestrictions,two defining constraintsof nonpotablereuseinclude:

Dual distribution costs:Dedicatedconveyancelines areneededto carry reclaimedwaterfrom productionto consumption.The capitalandoperatingcostsof suchdistributionsystemsareextremelyvariable,dependingon thevolume, distance,andfragmentationof thereuseapplicationsserved.Theyoftenhoweverrepresentthebiggestsinglecost in anonpotablereusesystem.In urbanapplications,thiscall for theinstallationofdual-distributionsystems,in whichreclaimedwaterlinesrun adjacentto drinking waterlines. Comparedto retrofits in existingurbanareas,dual-distributioncapitalcostscanbesignificantly reducedin newdevelopments,throughthe concurrentinstallationof potableandnonpotablelines.

Market developmentchallenges:Mostnonpotablereusesystemsrely on salesofreclaimedwaterto achievetheircostrecoveryobjective.However,the developmentofapermanentnonpotablewatercustomerbaserepresentsthemost significantchallengefor thereuseagency.Beyondpublic outreachprogramsneededto convincepotentialusersofthejustificationandinnocuityofreclaimedwaterservice,reuseagenciesneedto competitivelydisplacepotablewaterusage.Successfulpricing, marketingandconnectionassistanceprogramsareneededto thateffect.

3. A SURVEY OF NONPOTABLE REUSEMANAGEMENTPRACTICES

To promotesustainablenonpotablereuse,theWaterEnvironmentResearchFoundation(WERF)(Alexandria,Virginia, USA) hassponsoredan internationalreviewof nonpotablereuseplanningandmanagementexperiences.

Conductedby GénéraledesEaux, in collaborationwith Metcalf & Eddy Inc., theUniversityofCaliforniaandtheUniversityofNorth Carolina,theresearchrelies on anextensiveliteraturereview, amanagementsurveyencompassing65 systems(seeFigure2),andthe developmentof thematiccasestudies. Validatedsurveyresponseswereobtained

5THEMEN°2

for operatingsystemsin Australia(3) , Canada(i)~China(2), France(1), Israel(1), Japan(2), Namibia(1), Oman(1), Portugal(2), Spain(9), Tunisia(3), andtheUnitedStates(40).

All majornonpotablereuseapplicationswerecovered,including agriculturalirrigation,landscapeirrigation,groundwaterrecharge,environmentalenhancement,industrialcoolingandprocessing,toilet flushingandfire fighting. Productioncapacitiesrangedfrom lessthan4 million litres perday (MLD) to over400MLD. Industrialon-siterecyclingsystemsandmunicipallandtreatmentsystemswerenot includedin the survey.

The researchaimedin particularat documentingprovenandoriginal planningandmanagementsolutions,asexperiencedon operatingsystems,focusingon eight categoriesof issues:

- Institutionalframeworkandmanagementstructures- Planningprocesses,includingmarketassessments- Regulatorycomplianceandpermitting- Economicanalysisandcosts/benefitsallocation- Financialfeasibility andpricingstrategies- Legal& liability issuesofreuse,includingwaterrights- Programsfor communityeducationandparticipation.- Marketing strategiesfor growthandsustainabilityofreuse.

Thedatagatheredwasqualitatively analyzedfor trendsandexceptions.Given thesurveysampleheterogeneities,limited quantitativeanalysiswasperformedwith no claimtostatisticalsignificance.

Theresearchalsocreatedanewinformationresourcefor thewaterreuseindustry,in theform of adedicatedwaterreusemanagementwebsiteanddatabase.Initially reservedtoparticipatingagenciesandWERF subscribers,suchwebsiteincludesasearchabledatabaseofnonconfidentialsurveydata(encompassingthe eight selectedmanagementtopicslistedabove),summariesof dataanalysisresults,thematiccasestudies,aswell as industryreferenceinformation,contactsandlinks. The websitealsofeaturesan extensivebibliographyof reusemanagementissues,anddownloadablesampledocuments(studies,policies,contracts,ordinances,brochures,...)offeredby respondentsfor thebenefitof otherreuseplanners.

6THEME N°2

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Figure2: Geographicaldistributionof surveyednonpotablereusesystems

Participationof additionalagencies,throughonlineregistrationanddataentry, is possibleandencouragedto enhancethecontentandscopeof thisnewwaterreuseplanningandmanagementresource.

4. FINDINGS SUMMARY: NONPOTABLE REUSEMANAGEMENT ISSUES

Institutional framework

Thesuccessof awaterreusesystemcanbesignificantly impactedby the structureoftheagencyor agenciesthatconductits planningandmanagement.Therearefour generalplanningandmanagementstructureshavebeenidentifiedin waterreusesystems— projectsplannedandimplementedby awatersupplyagency,thoseledby awastewateragency,-ledprojects,integratedagency-ledprojects,andothers.This latter categoryincludesofad-hocreuseagenciesthatinterfacewith local sewerageandwateragenciesto supplyreclaimedwaterover regionsthatmayoverlapjurisdictionalboundaries.An integratedagencystructurewasthemostprevalentamongsurveyrespondents.

In spiteofthe different intereststhat eachofthesetypesof agenciespossess,therewasanunderlyingconcernfor thecostof developingnew waterresourcesthat led to thedevelopmentof manyof theprojects.Coordinationbetweenagenciesis importanttoensurethatunintendedimpactssuchasrevenuelossesfrom reducedpotablewatersalesarenot incurred.Integratedagencieswould appearto haveaninherentadvantagefrom thisstand-point, aswell asa reducednumberof interagencyagreements.Numeroussuccessfulprojectshaveneverthelessbeendevelopedby non-integratedagencies.The key to successiscommunicationbetweenthoseagenciesthatmaybe impactedby thereuseproject,eitherdirectly or indirectly.

Economicanalysis,cost& benefit assessment

Economicanalysisaimsat determiningif a reuseprojectis economicallyjustified, bycomparingprojectbenefitsandproject costsin monetaryterms.For nonpotablewaterreuseprojects,sucheconomicjustification is oftendifficult to ascertain,becauseof:

UncertainreclaimedwatersalesUncertaindisplacedfreshwatervolumes,Challengeto assessall costsandbenefits,including thoseof otheragenciesNeedto selectanoptimalplanningareaandprojectsizeto maximizebenefits.Difficulty in assessingthenon-tangiblebenefitsofreuse

7

THEME N°2

Tangiblecostandbenefits,specificto reclamationandreuse,aremonetaryin nature:

- Additional treatmentcosts- Reclaimedwaterdistributionandstoragecosts- Customerserviceretrofit andtrainingcosts(very oftenneglectedamongsurveyed

projects)- Savingsin avoidedwatersupplycapitalandoperatingcosts- Savingsin avoidedwastewatereffluent treatmentanddisposalcosts- Savingsin avoidedpermittingcosts- Shortfallsin potablewaterbillings andrevenue

Intangiblecostsandbenefitsaremoredifficult to quantify in monetaryterms, andinclude:servicereliability, public healthprotection,watershedprotectionandenvironmentalrestoration,andlocal economicdevelopment.Intangiblebenefitsweresystematicallyunaccountedin theeconomicrationalesof surveyedsystems.

Financial analysisand pricing strategy

Financialanalysisdeterminesif aproject canbefinanced,by assessingthat operatingrevenueswill coveroperatinganddebtservicecosts.Like anyotherwaterinfrastructureprojects,capitalfunding for waterreusecanoriginatefrom bonds,governmentalloansandgrants,aswell ascapitalcontributionby stakeholders(developers,industrial users,etc.).Waterpricing rationalefor mostsurveyedprojectsis drivenby theneedto provideincentivesto potentialcustomers,anddiscountingof reclaimedwateris consideredasthemosteffectiveincentiveto displacepotablewater. Only aminority of projectsaim theirpricingstrategiesat full costrecovery.By aiming for partial costrecovery,most projectsthereforerely on intra-agencyor interagencytransfersfor financialviability. Suchtransfersarefullyjustifiedwhenvaluing thefull benefitsof thereuseprogram.

Factorsenteringinto pncesettingprior to discountinginclude:- Marketabilityofreclaimedwaterquality- Costof distribution- Costof Retrofitting- Fertilizercontentvalue- Reliability

A wide variety of ratestructuresareapplied, including: Flat monthly charges(e.g. $/irrigatedha/month),quantityperunit volume (e.g. $/m3),basefee+ quantityperunit volume, declining block rate, “take-or-pay” guaranteedlump sum,etc.

All surveyedratesresultin reclaimedwaterpriceslower thanlocal potablewaterprices.In aboutone-thirdof surveyedUS projects,the reclaimedwaterpriceapproachedthatofpotablewater(i.e. greaterthan75%ofpotablewaterprice).

8THEME N°2

Managing risk & liabilities

While theregulationsgoverningreclaimedwaterarefairly well known, thelegal issues,suchasrisk andliability, associatedwith its usearemuchlesspublicized. Historically,adherenceto waterquality standardshasbeenusedto minimizehealthandsafetyriskstobothusersandproducersof reclaimedwater. Contractualagreementsbetweenthe retailerandthe useris theprimarymeansof limiting liability astheyrelateto quality and/orquantityof reclaimedwater,public healthissues,andpersonalinjury andpropertydamageclaims. Waterreuseagencieshavealsousedpilot studiesto assesstheir risk andlimitliability, particularlyin instancesof innovativereclaimedwateruses.

To date,theliability andrisk associatedwith theproductionanduseofreclaimedwaterhasnot manifesteditself. Developmentof conservativewaterquality standardsandthediligenceofthe reuseagenciesarethetwo primary reasonsfor this. Carefulconsiderationof theallowableusesofreclaimedwaterandrestrictionsto insurethat theseusesarepracticedin asafeandresponsiblemannerappearsto bea trademarkofthe successfulprograms.

Public outreach

With the exceptionof singleuser(institutional/industrial)projects,public outreachandeducationprogramsareanessentialcomponentof theplanningof reclaimedwaterservice.Comparedto overall programcosts,public outreachinitiatives arevery inexpensive.They dohoweveralwaysgenerategreaterpublic andstakeholderacceptanceof the project,andusuallyovercomethe instinctiveaversionof potentialcustomerstowardsreclaimedwater.

While differenttypesof outreachefforts (mailings,meetings,videos,...) may beaimedatspecificaudiences(generalpublic, customers,public officials, press,...)with differentgoals,thereis consensusamongsurveyedprojectson the needto pro-activelyinitiate sucheffortsduringthe planningphasesoftheproject.

Marketing and growth strategy

Marketing is oneof thekeysto successofreclaimedwaterprojects.A greatdiversityofstrategiesarebeingappliedto promotethe adoptionandtheconsumptionofreclaimedwaterby thetargetedcustomerbase.Essentiallyhowever,newcustomersaregainedthrougheithervoluntary(i.e. incentive-driven)participation,or mandatoryadhesion.The vastmajority ofprojectsrelieson voluntaryparticipation,in spiteof theoftensignificantassociatedriskof insufficientdeliveriesandrevenueshortfalls.This maydenotea lackofpolitical will or backingto imposemandatoryadhesion.Shortofmandatoryadhesion,aggressiveandflexible technicalandfinancialassistanceto customerconnectionretrofittingis avery effective incentivefor securingreclaimedwaterdemand.

9THEME N°.2

CASE 1: OUARDANINE, TUNISIA: LOCAL IMPLEMENTATIONOF A NATIONAL POLICY

Sincetheearly 80’s,Tunisiahasbeenoneof theleadingpromotersof agriculturalreuseoftreatedwastewater.It is in fact oneof thevery few countriesin themediterraneanbasinthathaveelaboratedandimplementedanationalreusepolicy andregulations.Early agriculturalreusesystemswere implementedby theMinistry ofAgriculture in collaborationwith theNational Sewerage& SanitationAgency (ONAS), andinclude theCebelairrigationschemaon theoutskirtsof Tunis.Planningandimplementationof suchearlyschemessufferedfrom insufficientmarketstudiesandunderstandingofgrowerspriorities(Bahri, Brissaud,1993).

TheOuardanineirrigation scheme,nearMonastir,offers anexampleof secondgenerationsystem.Until 1995 Ouardaninelived with theimpactsuntreatedsewagedischargedinto theOuedGuelta.Environmentaldegradationcombinedwith limited employmentopportunitiescontributedto manylocal youthleavingthis rural town. Calledto remediatetheuntreateddischargesituation,ONAS wasmetwith pressingdemandsby local farmersto reclaimthe

waterfor irrigation.While ONAS implementedanoxydationpondstreatmentsystem,theRegionalCommissariatfor AgriculturalDevelopment(CRDA) elaboratedan irrigationschemeprojectwith thefarmersregroupedin a formal GrowersAssociation(AIC). AIC wasresponsiblefor site selection,landrightsresolutionsandcultureselection.This hasallowedto easeuserestrictionsandavoid rejectionof reclaimedwaterby users.

Fifty hectaresof drip-irrigatedlandwere developed,as orchardsandpastures.In theabsenceofdisinfection,irrigation ofraw vegetablescannotbe allowed. Infrastructurecostswerecoveredby theGovernmentbudget,includinga2.5kmpipeline. Sincethestartofoperations,operatingcostshavebeencoveredby the Governmentbudget (75%) andby thegrowers(25%).

Theproject is consideredsuccessfulin that it hasachievedits environmentalgoals,whilecreatinga newyear-roundeconomicactivity (irrigatedcultures)andjobsin Ouardanine.Theprojectwasasuccessin thatit createdanewresource,andcommittednewusersto it, by

informingandinvolving themsincethe earlylocal planningstages.

The limited ability ofbeneficiariesto payfor thefull-cost ofreclaimedwateris expectedtoimprove astheorchardsreachmaturity. Expansionofirrigation capacityandirrigatedsurfaceis beingconsidered.

10THEME N°2

CASE 2: DURBAN, SOUTH AFRICA: MUNICIPAL PRIVATIZATION& RISK-SHARING

In orderto bettermanageandconservelocal waterresources,DurbanMetro Councilhasoptedto implementwaterreclamation& reuse,in particularfor industrial applications.Tothis end, theSouthernWastewaterTreatmentWorks is beingretrofittedwith advancedtertiarytreatmentprocessesto producehigh gradereclaimedwater, compatiblewith theusesofneighboringindustries,amongwhichpapermanufacturerMondi. Limited pipe laying isalsonecessaryto link thereclamationplant to thepointsofdelivery.

Underan innovativeprojectmanagementapproach,privatecontractorOTV wasselectedfor a20-yearcontractto design,build, own, operatethenecessaryfacilities, andeventuallytransfertheirownershipback to the City. The facilitiesconsistprimarily oftertiarytreatmentprocesses(coagulation,flocculation,filtration, disinfection)addedto existing secondarytreatmentprocessesatthe SouthernWastewaterTreatmentWorks(seeFigure3). Underthisscheme,the contractoralsotook responsibilityfor the guaranteeddeliveryandsaleof 42MLD ofhigh quality reclaimedwaterto the industrial clients(47 MLD capacity). Thissupplywillcover all processwaterneedsof theseindustrialusers.

Prior to designingthefacilities, it wasnecessaryto characterizethe feedeffluentquality toinsurethatthereclaimedwatercouldmeetthevery stringentquality specificationsset byMondi, the system’slargestclient, andpreviouslyauserofpotablewater.Underaverageflow andloadconditions,the contractordeterminedthatthespecificationscouldbemetandguaranteed.

Accordingly, theprojectwas designedto producereclaimedwatercompatiblewith theintendedindustrialusesfor anaveragepriceof 1.79 Rand/m3,thusaffording savingsof0.72Randlm3overprevailingpotablewaterrates.While committingto offer suchsignificantsavingsto the users,OTV will recoupits costby assessingthem aconnectionfeeandusagefees. Theusagefeesincludecapitalcostamortizationandoperatingexpensesaswellasatax to reimbursethe City for loss of potablewaterrevenue.Usersareguaranteedwaterdeliveryquotasthat includequality, quantity, andpressurecriteria,but arealsocommittedtopayfor thewaterwhetheror not it is used.

In casethequantityor quality influent primarywastewatersuppliedby MetroDurbanto thecontractorwereto significantlydecline(as contractuallydefinedby a setof “baseline”valuesof 24 waterquality parameters)operationalstorageandapotablewaterbackupsystemwill guaranteeacceptablecontinuousdeliveriesto users. Beyonda certaindeductiblecarriedby thecontractor,usersareto be chargedByLaw Pricefor all potablewaternecessaryto meettheQuality Specificationandquantitydemand.

Throughthis innovativecontractualmechanism,DurbanMetroCouncilachievesits goalsofmoresustainablewatermanagement,while sheddingmosttechnicalandcommercialrisksofreuseserviceto aprivatecontractor.

11THEME N°2

Fo~npflm~ty

4~6Mi/d

15MI/d

FLOW DIAGRAM FOR 47 500 m/d OF TREATED WATER

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Figure3: DurbanSouthernWorks: AdvancedTreatmentTrain for IndustrialReuse

ACKNOWLEDGEMENTS

This article is in partbasedon researchperformedby GénéraledesEaux(Paris,France)andMetcalf& EddyInc. (Wakefield, Massachusetts)for theWaterEnvironmentResearchFoundation(Alexandria,VA, USA).

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THEME N°2

RE-USE OF TREATEDWASTEWATER FOR GOLF COURSE

IRRIGATION, CASE STUDY:BEN SLIMANE

By A. FOUTLANE & B.A. YOUGOUBJ(ONEP)

TABLE OF CONTENTS

Page

ABSTRACT .15

I - INTRODUCTION .16

II - PRESENTATIONOF THE WWTPBEN SLIIMANE 17

III - WASTEWATER TREATMENT PLANT PERFORMANCES 18

Methodology 18

OverallPlantPerformance 19

IV - REUSEOF TREATED WASTEWATERFORIRRIGATION 20

RegulatoryAspects 20

PreventionandHealthSafetyMeasures 21

V - ECONOMICAL STUDY 22

SavingofDrinkingWater 22

CostEstimation 23

VI- CONCLUSIONS 23

REFERENCES 24

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Abstract

Commissionedin July 1997,theWastewaterTreatmentPlant(WWTP) of BenSlimane~locatedabout 80 kni awayfrom thecity ofRabat,is a resultof apartnershipin thefield ofpublic sanitationbetweenthemunicipalityofBenSlimane, theNationalOffice of DrinkingWater(ONEP)andtheCompanyMoroccoEngineeringRecreationsDevelopment(MILD).Financiallysupportedby the CanadianGovernment,thisproject is partoftheglobal strategy,whichaimsat environmentprotection andsavingofwaterthroughthereuseof treatedsewagefor irrigation ofthe Golfcourseandrecreationareaofthe city of BenSlimaneandpossiblythealongsidedagriculturalfields.

Thewastewatertreatmentsystemestablishedin Ben Slimaneisbasedon acombinationofnaturalwastestabilisationponds,improvedby slight aerationandcompletedby apolishingsystemof deepreservoirs.

The follow up oftheplant achievementsduring 1998hasshownthat:

* theWWTP performancein termsofremovalof carbonaceousandmicrobiological

pollution is sufficient* thebacteriologicalandparasitologicalanalysisof effluentsdo showvery

satisfactoryresultstakinginto considerationtheGuidelinesoftheWorld Health

Organization(WHO) relatedto irrigationof golf courses.

Giventhissatisfactorytreatedwastewaterquality of theWWTPBenSlimane,thereuseofthesetreatedeffluentsfor irrigation of the first part oftheBenSlimaneGolf course, •~

formerly irrigatedby drmlung water,hasstartedasfrom August1998 This approachhasall ~1owedfor: •

* anestimatedaveragesavingofdrinking waterofaround1,000m3/dfor theeftyof

BenSlimane.This savingof drinkingwatermight bedoubledor tripledby theeidof theprojectedsecondpartof theaforementionedGolf course.

* apositivedelayin reachingthe saturationstageof thedrinking watersupply

programmeofthe city ofBen Slimane.

Furthermore,it is worth to note that awarenessactionsfor thebenefitof treatedwastewaterreusers(Golfmanagement)havebeencarriedoutandaimedmainly at thesettingup andtherespectofpreventionmeasuresfor the staffworking in directcontactwiththeseeffluentsin orderto avoidanysanitaryrisk.

15THEME N°2

40

I - INTRODUCTIONThereuseoftreatedwastewaterfor different purposesandparticularlyfor irrigation is apractice,which is of growing importanceall over theworld andspeciallyin countrieswitharid andsemiaridclimates.In Morocco,annualsewageproductionratesin urbanareasareestimatedat around500hm3 (1). In this effect,andtakinginto accountthevulnerabilityofthecountryduringperiodsof prolongedcyclical drought,thesewatersmaybeconsideredasaprecioushydric resource,whose reusefor irrigation canbeconceivedasameanstoconservefreshwatersources,which is steadilybecomingrare.In this context,severalinvestigationshavebeencarriedout in differentregionsofMoroccoto promotea rationalandmasteredreuseof treatedwastewaterin agriculture: Ouarzazate(2), Marrakesh,Rabat(3) andAgadir (4).

Thus, theaim of wastewatertreatmentshallcontributenot only to theprotectionofhygieneandpublic health,to thepreservationof waterresources,butalsoto the mobilizationofhydric resourcesin thecontextof its rarity. Properwastewatermanagementis consideredasanessentialcomponentofthedevelopmentofthe drinking watersector.

In this spirit andwithin the frameworkof an exemplarypartnershipin the field ofsanitation,linking togethertheMunicipality ofBen Slimane,beingthe entity in chargeofwastewaterpurification,thecompanyMILD (Maroc IngénierieLoisirs Développement)actingasaprivatecontractorin chargeof theoperationoftheWWTP andONEP(NationalOffice ofDrinking Water) asapublic operator,theprojectof realisationof awastewatertreatmentplant for the city ofBenSlimanewasinitiated.This plant couldonly be realisedwith thefinancialsupportby theGovernmentofCanadagrantedto thisprojectthroughONEP.

ThedocumentherebypresentssuccinctlytheperformanceresultsoftheWWTP BenSlimanewith thecorrespondinginvestigationscarriedoutjointly by ONEPandMILD during1998. It alsoshowsthepracticalapplicationandthebeneficialeconomicaleffectsof theeffluent reusefor the irrigation of theGolf courseof thecity of BenSlimane.

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II - PRESENTATION OF THE WWTP BEN SLIMANE

TheWWTP Ben Slimane,locatedabout50km awayfrom thecity of Rabat,is basedon thetypicalwastestabilisationpondsystemandis designedfor awastewaterflow of5,600m~/din orderto meettheneedsoftheurbancentreat leastuntil theprojecthorizonof theyear2010.

Thepresentpopulationofthis city is around37,000inhabitants.

ThemajorobjectivesofthisWWTP areasfollows

* theprotectionof both theenvironmentandpublichealth

* thecreationofanadditionalhydric resourcethroughthereuseoftreated

wastewaterfor theirrigation ofGolfcourses

* the developmentoftheregion’stounsticpotentials.

TheWWTP BenSlimanecomprisesthefollowing 4 main treatmentprocesses(5):

* apre-treatmentsystemconsistingoftwo parallelunits, eachdisposingascreenanda

sandremovalfacility, thusallowing for mechanicalwastewatertreatment,

* aprimary treatmentsystemconsistingof 5 anaerobicpondsof 3,500m3 each,with the

following principal operatingparameters:avolumetricloadingof 100 g BOD5/m3/d

in winter and200 g BOD5/ m3/d in summerwith a retentiontime of2 to 3 days,

* asecondarytreatmentsystemconsistingof4 facultativeponds(2 largepondsof

20,000m3 each,and2 smallerpondsof 13,000m3 each)operatingwith a totalretentiontime of 2 weeksandasurfaceloadingof 150 kg BOD

5/ha/d.Thesepondsarepreceededby 4 aerationpondsof5,000m

3 each(operatingat oxygenconcentrationsof 2 to 4 mg/l anda retentiontime of 3 to 4 days),

* a final polishingsystemconsistingof 4 deep,socalled“operational”reservoirsof

75,000m3 each,andof 5 m depth.Theretentiontime for thistreatmentstageis about30 to 40 days.

17 ~THEME N°2

It is worthto notethat thesedeepreservoirsoperatein four phases:

* a filling phase

* a storageandmaturationphase

* anemptyingphasefor eithertheirrigation of theGolf courseor thedischargeinto

thenearbyriver,

* aphaseof inactivity (slackperioduntil thebeginningof thenew cycle).

Thusit canbesummarised,that thewastewatertreatmenttechnologyof this plant is basedon acombinationof naturalwastestabilisationponds,improvedby slightaerationupstreamandassociatedwith a final wastewaterpolishingsystemby meansofdeepreservoirs.

III - WASTEWATER TREATMENT PLANT PERFORMANCES

Methodology

TheperformancesoftheWWTP BenSlimanehavebeenevaluatedby following up themainphysicalandchemicalwastewaterparameters(COD, BOD5, TSS,TKN andP~0~)aswell asthemicrobiologicalparameters(fecalcoliformsandparasites)at the inlet andoutletoftheplant.Theadoptedsamplingfrequencieswere2 to 4 timesduringthefirst semesterandamonthly frequencyduringthe secondsemester.24hrs compositesampleshavebeentakenattheplant inlet, whereasgrab sampleshavebeentakenattheplant outlet.However,samplesfor bacteriologicalanalysishavebeentakenas grab samplesat theplant inlet aswell asattheplant outlet.Moreover,all sampleswereanalysedaccordingto the analyticalmethodsusedatthe centralLaboratoryof ONEP,whicharegenerallyequivalent to theinternationalstandardmethods(AFNOR, StandardMethods,ISO ...).

18THEME N°2

Overall Plant Performance

As shownin thetable 1 belowtheaveragetreatmentefficiencyoftheWWTP Ben Slimanehasbeenfoundto besufficient:

Table 1: Overall Treatment Efficiency oftheWWTP Ben Slimane (1998)(all analysisresultsareaveragefigures)

Parameters Unit Plant Inlet Plant Outlet Reduction

(%)

EEC

PrescriptionBOD5 mgO2Il 130 28 78 79—90COD mgO2/l 450 84 79 75TSS mg/l 157 20 87 90TKN mgN/l 51.2 12.7 75 70—80

P~0~ mgP/l 9.9 5.8 41 80Fecal Germs/lOUml 6 logU

IV- REUSE OF TREATED WASTEWATER FOR IRRIGATION

RegulatoryAspects

Basedon thefact, that thereuseof treatedwastewaterof theWWTPBenSlimaneismainlyorientedtowardstheirrigation oftheGolf course- whichmight imply directhumancontactwith thegreenfields - themain quality criteriaconsideredis themicrobologicalwastewaterquality in orderto avoidanyhealthproblem.

In this contextit is importantto takeinto considerationthecorrespondinginfectingdose,whichrepresentsthe numberof micro-organismsnecessaryto infect avulnerableperson(9).This doseis very low for parasitessince thepresenceof only oneparasiteeggmightalreadybesufficient to causediseases.On theotherhandfor bacteriaoftenhundredsoreventhousandsof germsmight benecessaryto leadto an infection(9,10).For thispurposethe effluentquality oftheWWTP BenSlimanehasbeencomparedwith theGuidelinesoftheWorld HealthOrganization(WHO) for the microbiologicalquality of treatedwastewaterto beusedfor irrigation (11),which takeinto considerationthesehumanhealthrelatedaspects.

The abovementionedmicrobiologicalindicatorsof thetreatedwastewaterhavebeendeterminedby meansof analysisrealisedfor samplestakenfrom thedeepreservoirsduringits emptyingphaseor during theadvancedmaturationphase.Basedon theseanalysisresults,thefollowing hasbeenconcluded:

* for all samplescollectedduringtheinvestigationperiodtheanalysisresultsoffecal

coliformsdid showvaluesbelow20 FC/100ml,

* in termsofparasitologicalwastewatercharacteristicsthetreatedwastewateratthe

plantoutlet is freeofHelmintheggs.

Theseresultsconfirmedthatthemicrobiologicalquality ofthe final effluentoftheWWTPBenSlimanemeetstherequirementsof theWHO guidelinesrelatedto its reusefor theirrigation ofgreenfieldssuchasGolf courses.

It thuscanbe concludedthatthespecificdesignobjectiveofthisWWTP - to avoid anypotentialtransmissionofdiseaseswith hydric origins - hasbeenmet. It shouldbe notedthatthewastewatertreatmentplant is alsoequippedwith achlorinationsystemasstandbyfacility,whichcould beput in operation,if required,to furthermoreimprove themicrobiologicalquality ofthetreatedeffluentsor in caseofanoutbreakof contagiousdiseasesofhydricorigin (Hepatitis, Cholera, typhus ...) in theregionofBen Slimane.

20

THEME N°.2

Prevention and Health SafetyMeasures

It is evident,thattherecyclingof treatedwastewaterwould only be successful,if all publichealthandsafetyrelatedquestionsaretakeninto consideration.In fact, it is importanttomention,thateventhoughspecificwastewatertreatmentobjectivesaremet,acertainrisk forpublic health always remains. This leadsto the needfor preventionandawarenessmeasuresfor the operators being in contactwith thesetreatedwastewaterson both sites — the WWTPaswell asthe site ofthe effluentreuse(in caseofBen Slimanethegolf course).

In caseof BenSlimanethetreatedwastewatersaredischargedinto a small lakeofthe Golfcoursebeingreusedfor irrigation.Thereforethemostimportantstaffpreventionmeasuresestablishedin this contextarethosestatedin theW}lO recommendations(11):

* thebanningof reusedtreatedwastewaterfor drinking, for anydomesticactivity or

for swimming purposes. Corresponding warning signswereputup for thispurpose,

* the wearing of specialprotection clothes(gumboots,cap,gloves,protection suits.),

which should be keptcleanandseparatedfrom personalclothes,

* daily hygienemeasures,with specialrecommendationsto washwith cleanwaterafter

any directcontactwith thetreatedwastewaterandto possiblytakeashowerat theendof work,

* preventionfrom takingmealsin placesofcontactwith wastewater.

* obligationto bevaccinatedagainsttetanusandto renewvaccinationevery5 years

(vaccinesagainstpoliomyelitis, typhoidandsimilar diseasesarerequiredtoo).Moreover,it is recommendedto neverneglectscratches,not eventhe smallestones,todisinfectthem (with an appropriatedisinfectant)andto putadressingon them.

TheGolfmanagerhasbeencalleduponto implementthenecessarymeansto allow for therespectof theserequirements.

ONEP, in collaborationwith MILD andthe Municipality of thecity ofBen Slimane,haselaboratedsensitization leaflets to the benefit of the staff workingon theWWTP aswell asofthe staffon thegolf coursepotentiallycominginto contactwith treatedeffluents.Thementioneddocumentspointout thepossiblesanitaryrisksof treatedwastewater,andstatehygieneinstructionsto be followed, whichconstitutethemosteffectiveprotectionbasisagainsttherisksof infectiousdiseases.

21 ~41THEME N°2

V - ECONOMICAL STUDY

Saving of Drinking Water

The limited waterresourcesofthe city of BenSlirnanemadeit necessary,thatsince 1996the drinking watersupplyofthis city is supportedby thewatertreatmentplant locatedat theBou Regregcomplexin Rabat.

Only togetherwith waterfrom this plant (with adistanceofaround50 km to Ben Slimane)it is possibleto meettherequiredwateramountof around170us.The saturationhorizonofthisprojectwould betheyear2015aslong astheproducedwaterwouldbeusedexclusivelyfor humanconsumptionandindustrialuses.

Furthermore,it shouldbenoted,that thetourismis presentlyconsideredasa very importantfactor for theeconomicdevelopmentofthis region,with theimplementationof the Golfcoursebeingoneof themain componentsof thetouristic infrastructure.

Takinginto considerationthehugewaterrequirementfor irngationof agolfcourse,theuseoftreatedwastewaterfor thesepurposesrepresentedtheuniquesolutionto savedrinkingwater.The amountof irrigation waterneededfor the currentlyoperationalGolfcoursesisestimatedto around33 us,beingequivalentto around3,000m3/d.This amountis expectedto reachapproximately5,000m3/dby thetime ofterminationof theplannedgolfcourseextension.Consideringtheraw wastewaterflows of thewastewatertreatmentplant asrecordedduringthe investigationperiodandshownin figure 1 below, it can be concluded,thatthetreatedwastewaterquantitycouldwidely coverthepresentneedsfor theGolfcourse irrigation.

800070006000500040003000

~ 20001000

0

Date oftakingFigure 1: Raw WastewaterFlow of the WWTP Ben Slimane during 1998

Effectiveirrigation oftheBenSlimaneGolf coursewith treatedwastewaterhasonly beeninitiatedin august1998, afterthegolf coursemanagementhasbeenassuredtheplantperformanceaswell astheconformityofthetreatedwastewaterquality.Fromthis time on, a firstpartof theGolf coursehasbeenirngatedwith treatedwastewaterat anaverageflow of2,000m3/d,which - dueto thefact, that theabovementionedlakehasbeenfilled up in themeantime— hadto bereducedto around1,000m3/d.The savingof drinking waterfor thecity of BenSlimaneis thereforeestimatedon an averageuseof treatedwastewaterof 1,000m3/d.

22THEME N°2

00~00•00~— — —— — —

r~ —~ —

00

—

00

00

00 00 00

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~n •1~~ —

00

F—

00 00

— —~— e-~

00 00

F— 00

— -—c,-’ —(~-1 —

00 100 l

00

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— —

Cost Estimation

Investment Costs

The investmentcostsof theWWTPofthe city ofBen Slimane,realisedin 1997, amounttoaround96.44million dirhams(DH) *).

*) 1 Dirham(DH) = 0.104US$

Operation Costs

The evaluationof theplant operationcostsfor theperiodJuly 1997 I June1998areshownintable 2 below.

Table 2: Yearly Operation Costsof the WWTP Ben Slimane(OperationPeriod:July 1997- June1998)

Cost Item Operation Costs(DHlyear)Staff 589,255Energy 196,045Laboratory 24,000Maintenance 20,410Cleaning 15,200Miscellaneous 90,874TOTAL 935,784

-~

Cost price~#~_

The costs for the produced treated wastewater amounts to around 1.45 DH/m~Considering the current selling price of the treated wastewater being 2 DHIm3, it i8 worth to ~mentionthat thiskind ofdealis profitable for thewastewatertreatmentplant management.Furthermore,alsofor the golfcoursemanagementthisdealworksout quite well, siiicepresentlythepurchasepriceofdrinking waterperm3 is around4 DH, which is significantlyhigher (double)thanthecurrentpriceof2 DH perm3 of treatedwastewater.

VI- CONCLUSIONS

Thispilot projectof treatedwastewaterreuseoftheWWTPBenSlimanefor irrigationofthenearbyGolf courseshowsverypromisingfirst results,sinceit allows for aconsiderablesavingofdrinking water along with promotingthetouristicdevelopmentofthe region.Thissavingof drinking waterfurthermoreallowsfor a delayof importantinvestmentsbecomingnecessaryfor thereinforcementofwaterproductionfacilities in orderto meettheregion’sdrinking waterandindustrialwaterdemand.

23THEME N°2

The treatmenttechnologyofwastestabilisationponds,with aspecificapplicationnewlyintroducedto Morocco,hasallowedto meetthe specifiedobjectiveswhichareenvironmentprotectionandthecreationof anadditionalhydric resourceof aquality conformto a reusefor irrigationof greenfields. This approachis perfectlyappropriateto thesocio-economiccontext of Morocco and opens new horizons as far asthereuseoftreatedwastewaterinMorocco is concerned.The futureapplicationof similar projectsin smallandmediumsizecommunities may representa goodoptionfor appropriatemanagementandregenerationofwaters, and particularly under conditions ofwaterrarity.

REFERENCES

1- ConseilSuperieur de 1’Eau et du Climat du Royaumedu Maroc. (1993)RéutilisationdeseauxuséesenAgriculture. 8emeSession.2- Ministèrede l’Agriculture et de la Mise en Valeur Agricole du Royaumedu Maroc.(1994) Réutilisationdeseauxuséesa desfins agricoles.ProjetM0R86/01 8PNUD,FAO. OMS. Janvier1994.3- Kawni.A et J. Darley.(1996)La réutilisationagricoledeseauxuséesépuréesauMaroc.Direction de l’Eau et de l’Assainissementde la DGCL (Ministère de l’intérieur du Royaumedu Maroc).Décembre1996.4- I.A.V. HassanII., ORMVA/soussMassaet RAMSA. (1996)Epuration des eaux uséesetleur valonsationdansl’agriculture . Casde la communeurbainedeBenSergao,Wilayad’Agadir.5- Municipalité de Ben Slimanedu Royaumedu Maroc., TAHAL consulting engineersLTD., MILDEAS et ONEP. (1997) Stationd’épurationetde recyclagedeseauxuséesdeBen Slimane.Manueld’exploitation..Juin1997.6- CEE. (1991)Directivesdu Conseildu 21 mai 1991 relativesau traitementdeseauxurbainesrésiduaires.Journalofficiel descommunautéseuropéennes.7- ONEP-GTZ. (1998)TypologiedeseauxuséesurbainesauMaroc. Cooperationtechniquemaroco-allemande,juin 1998.8- Echihabi. L.,A. Foutlane.,A.Yagoubi.,J. Bahij.,A. Maghrabi.,Y. Loulidi etA. Lahlou. (1999)Evaluationdesperformancesépuratoiresde la stationd’épurationdeseauxuséesde la ville de BenSlimaneauMaroc - TypeLagunage-9 - Prost.A. (1987)Lesdangersdemaladiesinfectieuseslies a la réutilisationdeseauxusées.Bulletin de qualité deseaux,OMS,juin 1987.10- Saenz.R (1987)Irrigation avecdeseauxuséesépuréesenétangsde stabilisation—Evaluationdesaspectsmicrobiologiques.Bulletin de qualitédeseaux,OMS,juin 1987.11-World Health Organization.(1989)Healthguidelinesfor theuseofwastewaterinagriculture and aquaculture. Report of a WHO scientific Group. Technical ReportSeries 778. Geneva,1989.

24THEME N°2

THEME N°2

RECYCLING OF WASTEWATER

AND ITS SUB-PRODUCTS

By GueladioCISSE (EIER)

10th UADE CONGRESS,DURBAN, SOUTHAFRICA (February 19-252000)

Topic: Reuseofwastewaterandpurification by-productsin Africa

WASTEWATER REUSE IN URBAN AGRICULTURE IN THESAHELIAN CONTEXT

HEALTH RISKS, ECONOMIC ASPECTSAND TECHNOLOGICALCONSTRAINTS.

Dr. GuéladoCISSE,EIER, Ouagadougou,BurkinaFaso

ABSTRACTAs a resultoflimited water resourcesin arid zones,particularly in the Sahel,wastewaterre-

usehasbecomean essentialcomponentof integratedmanagementofwater resources.One

finds therea re-usepracticeofanykindsofwastewaterwithout anyplanningand control inurbanagricultural activities.

Economicand social interestof urban agriculture, existenceofvarious “fait accompli”,utilisation ofpollutedwaterbypopulationshardlyawareofhealthrisks, weaknessofinstitutionswhichare likely to enforcehealth instructionsor to establishplantsfor collectivetreatment

ofwastewaterandthe needfor scientiststo contributetowardfinding solutionsto improve

thesituationofactors themselvesconstitutethemain stakes.

Until a recentperiodfewstudieson wastewaterre-usein saheliancountrieswereavailable.TheEcoleInterEtatsd’Ingemeursde l’EquipementRural(EIER) inpartnershipwith theEcolePolyteclmiqueFédéraledeLausane(EPEL)and the InstitutTropicalSuisse(ITS) havebeenconductingsince1994multidisciplinaiyresearchstudiesonwastewaterre-usein urbanmarket-

gardeningin saheliancountriesparticularly with an epidemiologicalperspective,associatedwith microbiology,socio-anthropology,cartographyandgeomatics.

Thestartingpoint oftheresearchprogramwastheproblemofhealth risksrelatedto theuse

ofpolluted water in urban market-gardeningin the aridity contextofsaheliantowns andresultedsince1997in theestablishmentof interactiveprocessesofsustainabledevelopment

at local level.

Thisarticlepresentsthelessonsdrawnfrom thisresearchprogram throughoutmanyyearsin

order to contribute to the needto pursueand to disseminatethe knowledgein thisfield.

Key words: Sahel,urban market-gardening,wastewaterreuse,health impact, integratedmanagement,participatorydevelopmentat local level.

26THEME N°2

INTRODUCTION

Whenever”re-useof wastewater”ismentioned,for commonsense“plannedandcontrolledchoice“must be understood.Following this understanding,the commonquestions,amongothersareas follows: What bestpurificationtechniquescanmakewastewaterre-usepossible?What standardsmustbefollowed in order for its risks-freere-use?Whatmeasuresmust betakenin orderto ensurethecontrol ofperformancesofestablishedsewagetreatmentsystems?But in manyAfrican countriesonecanfind wastewaterre-usewhich doesnot follow anyplanandwith no mechanismto controlthequality of thewaterusedfor thewateringofvegetables,evenif thelattercanbe eatenraw.

The populationexplosionandthe dazzlingextensionof African towns,particularlyin pen-urbanzonesaswell asurbanisationleadto an increasein waterdemand(Coulibaly, 1998).Thiscausesan increasinglyimportantproductionof wastewaterwhich is left in streets,channelsandguttersby thelackof sanitationinfrastructure.

In saheliancountries,market-gardeningis commonlypractisedin urbanand peri-urbanenvironment.Accordingto acertainnumberof studiesconductedtheserecentyears,about200 million urbandwellersof developingcountriesareurbanfarmerstoday. Urban farmersusevariouswatersourcesfor wateringtheir vegetables:well water,waterfrom dams,waterrunningin guttersanddrainagechannels.

The conditionsof waterscarcityon market-gardeningsites in arid zonesmay bring aboutextremessituations:somesitesuseuntreatedwastewaterrunningin guttersor rainwatersewerswhichmaycomefrom householdsaswell asfrom industries.

In arid andsemi-aridregions,wastewaterre-usefor imgationis widely practised(Blumenthalet al., 1989; StraussandBlumenthal, 1990;Hispanhol,1990). Moreover,thepracticeofwastewaterre-useis widespreadin otherregionsof the world; it existsin both developedcountriesanddevelopingcountries.Someauthorsthink that” wateris a very rareresourcetobeusedonly oncebeforeit is returnedto nature...“ (SandbergH., 1992). However,it onlysince a few yearsthatwastewaterre-usehasbecomeamatterofscientific, sociologicalandeconomic interest mdiscussions about the concept of mtegrated management of water resources.SomeAfrican countriessuchasTunisia andSouthAfrica havemadewastewaterre-useanationalpriority (Le Vine Renaud,1998).

Until a recentperiodvery few studieson wastewaterre-usewereavailable.The EcoleInterEtatsd‘Ingénieursde 1 ‘EquipementRural (EJER) in partnershipwith theEcolePolytechniqueFédéraledeLausanne(EPEL) andthe Institut Tropical Suisse(ITS) havebeenconductingsince 1994multidisciplinaryresearchstudieson wastewaterre-usein urbanmarket-gardeningin saheliancountriesparticularlywith an epidemiologicalperspectiveassociatedwithmicrobiology,socio-anthropology,cartographyandgeomatics.

Economicandsocial interestofurbanagriculture,existenceofvariousfait accompliutilisationofpollutedwaterby populationshardlyawareof healthrisks,weaknessof institutionswhichare likely to enforcehealthinstructionsor to establishplantsfor collective treatmentofwastewaterandtheneedfor scientiststo contributetowardfinding solutionsto improvethesituationof actorsthemselvesconstitutethemain stakes.

27THEME N°2

GENERAL PROBLEM

Health risks related to wastewaterre-use

Therearefour categoriesofpeoplefor whomagriculturalutilisationofwastewaterrepresentsa “potential“risk which is differentfrom “real” risk (Mara et al., 1992): (1) field workersworking in the fieldsandtheirfamilies; (ii) handlersandfield workersresponsibleof crops;(iii) crop consumers(people and livestock); (iv) people living near fields.

WHO instructions for wastewaterre-use

Themain pointsofWHO recommendations(OMS, 1989)are: (i) - theutilisationof raw wastemust be bannedin any circumstance;(ii) - In anycasethewaterutilised must containanarithmeticalaverageof lessthananeggof intestinalparasiteperlitter; this is oneofthenewrequirementswhich goes toward strengthening standards; (iii) - the microbiologicalqualityof the water mustbemonitoredin thecaseofvegetableswhichcanbeeatenraw, irrigationof recreation areas and whena sprinklingmethodis used;this watermustcontainlessthan10 faecal coliforms per litter; (iv) - amoredrasticstandardof lessthantwo thousandfaecalcoliforms will be applied to grass public has direct contact with like in hotels.

Needfor a multidisciplinary approach

Intheevaluationofhealthrisksrelatedto wastewaterusein two saheliancountries,theresearchprogramhascombinedin a transdisciplinaryapproach,cartography(spatialpositioningofenvironmental phenomena), microbiology (evaluation of potential risks), sociologyandanthropology (shedding light on risk factors), epidemiology(evaluationof real risks) andgeomatics (analysis of spatial dimension).

Geomatic approach

Enviromnentalfactorsin urbancontextbeingparticularly localised,geomaticsis todayanessentialdiscipline for abettermanagementofurbanenvironments.The geomaticapproachwas givenprimeimportancein the frameworkofthis study.

An exhaustivegeographicalsurveywascarriedoutin 30 sectorsofthe city of Ouagadougouaboutmarket-gardeningsites, wastewaterandsolid waste.Severalmethodsandtools havebeenusedincluding aGPS(GeoPositioningSystem)machine.The datacollectedby the

28THEME N°2

GarminGPS machinewereconvertedwith aGarminPCX5softwareandtreatedwith anExcelsoftware.Moreover,an epidemiologicalsurvey,covering these30 sectorsof the city, ondiarrhoeaamongchildrenof lessthan5 years.The datacollectedby the surveyorswerekeyedin with varioussoftwaresaccordingto the following method:EPIINFO softwarefor thequestionnaires;Excel for thegeographicalsurveyforms.The basicmapof Ouagadougouwitha 1/10,000scalewasdigitilized aswell asthethematicmaps.The summaryof the dataandthepresentationoffindings at thelevel of the sectorhavebeencarriedout with theMapinfosoftware.

Thegeomaticapproachmadepossible(i) - to characteriseresidentialsectorsin Ouagadougouaccordingto refusedumpsandwastewaterdischarge,(ii) - to positionmarket-gardeningsitesin urbanstructureand(iii) - to evaluatetheimportanceofcultivatedsurfacesduringthe dryseason,thecool seasonandtherainyreason.

Thegeomaticapproachalsomadeit possibleto breakup the mainresultsoftheepidemiologicalapproachin order to presentit at the level ofthe sectorunderthe form of thematicmaps.

MARKET-GARDENING SITES IN THE URBAN STRUCTURE

Situation in Nouakchott

Nouakchottcomprises7 main market-gardeningsites(SchneiderandGagneux,1997).TheSebkhasite, locateddowntown,constitutesthe oldestmarket-gardeningareaestablishedaspartofthe installationof asewagetreatmentplant (STEP)in 1965.The sewagetreatmentplantwasthebacteriologicalbedtypewhosewastewaterwasfeedingadistributionnetworkofwatertreatedby STEP designedfor 72 plots (Ould Baba, 1999). Utilisation problemsled to acontinuousdeteriorationof purification capacitiesuntil thetotal breakdownoftheplant ~i1979.This interruptiondidnotpreventthecominguntreatedwaterfrom runningto themarket-gardeningsitesdespiteacertainnumberof studieswarningabouthealthrisks(Sidatt, 1979;Sidatt, 1982).A rehabilitationprogramlaunchedin 1990with help from ADB (CIEH, 1992)resultedin 1992 in the installationof a sewagetreatmentplantwith activatedsludge.Thewastewaterundergoesa tertiarytreatmentby chiorationbeforebeingpumpedbackinto thedistributionnetworkof themarket-gardeningsite. Wastewatermonitoringis undertakenforphysico-chemicalparameters;On theotherhand,bacteriologicalandparasiticalpollution(concernsofWHO instructions)arenot analysed.

Therefore,in Nouakchott,it is a situationof intentionalwastewaterre-use“plannedsituation”of whichcontrol was lostbetweenfrom 1979 to 1992 (“ Situationnot under control “), andwhich is comingbackto normalafterthe 1992rehabilitation(“ situationundercontrol “ evenif thiscontrolis still limited.

29THEME N°2

Situation in Ouagadougou

In Ouagadougouthereis no public networkofwastewatercollectioninto a STEP.Thereis asewagetreatmentplant with activatedsludgefor wastewatercoming from thecentralmarketwhichhasbeensetup since1998.A studyconducteda few yearsonly afterthe installationofthemarketSTEPrevealedthat thequalityof thewatercomingfrom theSTEPwasalreadyfar beyondthedischargestandardscontainedin the termsof reference(CREPA, 1991).Thewastewaterfrom this plant is pumpedinto anopenchannelwhich runs into the listedforestwherethiswatercomestogetherwith anotherwaterfrom ahydrographicnetworkandconvergein thisplace.Wastewaterfrom Kossodoindustrialarea(Slaughterhouse,SOBBRA,TanAliz) alsocomesinto this convergenceplace(shallow) of run-offwater. An importantmarket-gardeningactivity is undertakenin this shallowareaalongpollutedwaterflowing ingutters(Cissé,1997).

Market-gardeningactivity in Ouagadougouis usuallyseenalongdamwaterandwell waterbutalsoin manycasesalongwastewaterdischargesthat arefoundin channelsandgutters(Abattoir, SOBBRA, Tannery,CentralCanal,Kossodo).One canfind 48 placesor market-gardeningsites appearing occasionally orpermanentlythroughouttheyear(seethegeographicallocationof thesesites in Figure 2). The waterusedin theseareascomefrom wells, dams,gutters,pondsor openchannelsfor rainwaterdrainage.

Provisionhasbeenmadein thePlanStratégiqued’Assainissementdela Ville deOuagadougou(PSAOor StrategicPlanof Sanitationfor thecity of Ouagadougou)for the establishmentofacollectivetype of sanitationnetworkwhich includesthecollectionandtreatmentof urbanwastewaterandindustrialwaste(ONEA, 1993).This collectivenetworkwill not deal,on theonehand,with sectorshavinganurbanisationwhich is denseenoughand,on theotherhand,with big wastewaterproducingsettlements.Wastewaterwill be carriedtoward a sewagetreatmentplant by lagooningin the Kossodoshallowwhereits re-useby market-gardenersfrom this site hasbeenplanned.

It is, therefore,in thecaseof Ouagadougouasituationof wastewaterre-usewhich is presentlynot intended“unplannedsituation” which is not undercontrol yet “ situationnot undercontrol “) butwhich shouldchange,with PSAO, into an intentionalsituation(“ plannedsituation“) “undercontrol”

30THEME N°2

POTENTIAL RISKS

Two approacheshavebeencombinedin orderto evaluatepotentialrisks: acartographicapproachandamicrobiologicalapproach.

The cartographicapproach,with the contributionofgeomatics,madepossible(i) - to characterisethe residentialsectorsof thecity accordingto pollution from refusedumpsandwastewaterdischarges,(ii) - to positionmarket-gardeningsitesin theurbanstructure,and(iii) - to evaluatethe importanceof cultivatedsurfacesduringthe dry season,the cool seasonandthe rainyseason.The epidemiologicalapproachmadeit possibleto follow thebacteriological(faecalcoliforms) andparasitical(helminthandprotozoaeggs)pollutionofwater, soilsandvegetables.

In Ouagadougou,thefollow-up for two consecutiveyearsofwatertypesusedfor wateringin4 main market-gardeningareasin Ouagadougou(Slaughterhouse,CentralCanal,Tanghin,Boulmougou)revealedthatall thewatertypes,evenwell water, containabacteriologicalpollutionwhichis usuallymorethanthelevelsrecommendedby WHO for wateringvegetableswhicharelikely to eatenraw (Table 1). Waterfrom guttersandopenchannelshavethemostimportantlevelsofpollution (respectivemedians5.9 l0~and 1.4 106 respectivemaximums2.2 10~and9.4 107),equallinglevelsof raw wastewater.Theyhappen,then,to bemoreharmfulfor health, particularlyin regardto parasiticalresults(Figure 1). The market-gardeningestablishedalongthesewatertypes(for example,SlaughterhouseandCentralCanal),thus,display thehighestpotentialhealthrisksfor market-gardenersandtheir families (Cissé,1997).

In Nouakchott,analysesoftreatedwastewatercomingfrom theSTEPhavefounda bacteriologicalpollution level whichcomplieswith WHO instructions(SchneiderandGagneux,1997).Onthe otherhand,thepollution levelsofthe waterin farmers’wateringbasinshasa medianof9 1 10~CF/100ml This increaseof pollution in thebasinsmightbecausedby awidespreadpracticeon sitesin Nouakchottwhich consistsofenrichingwaterfrom thebasmby pourin~g ~in it sacks of poultry manure

31THEME N°.2

REAL RISKS

Two epidemiologicalapproacheshavebeencombinedin order to evaluatereal risks: Theexposed(versus) non exposed“ approachand the “ control (versus) case“.

In Ouagadougou,the study of” exposed- non exposed”typetargetingchildrenconductedin 1995 (Cissé,1997)hasrevealedthatmarket-gardeners’childrenagedlessthan5 show, inasignificantway,higherprevalencesthanchildrenofthesameagein the populationin generalof Anakylostoms (10.80 6.68%against1.40 0.43%,RP = 8.45, p

THE ROLE OF ACTORS IN THE PROBLEM

Thereareotherstepswhich follow theproductionofvegetables(market-gardeningsites),suchassale in markets,sale in small restaurants,andpublic or private consumption.The actorsmvolvedin theproblemarethereforevanous:farmers,retailers,tradersandpublicconsumers.The economicandsocial aspectsof market-gardeningactivity areimportantthroughthesevariousactors.Market-gardeningandtheavailability ofwastewater,whichpermitsit, providehundredsof families in both citieswith an activity andincomeswhich cannotbe neglectedTo evaluatetherole ofactorsin thehealth-riskschain,asocio-anthropologicalapproachmadeit possibleto collectvariousactors’attitudesandbeliefs in thedistributionline of vegetables(from producerto consumer),andto proceedwith direct observationsofenvironmentalfactorsaswell practicesin thevariousplacesofthis line.

TECHNOLOGICAL CONSTRAINTS

To be health-risksfree, plannedor unplannedwastewaterre-userequiresthe adoptionoftechnologicalsolutionswhicharenot easyto find, to setup andto use.

In thecasesofplannedre-use,technologicalconstraintsarerelatedto problemsofutilisationandmaintenance.A studyconductedby CIEH (CIEH, 1992) in acertainnumberof Africancountrieshighlightedtheweakpercentageofsewagetreatmentplantswhicharefunctioningadequatelya few yearsaftertheir installation.

In thecasesof unplannedre-use,technicalsolutionsto reducepollutionaredifficult to setupwith farmers:protectionof wells,changein irrigation techniques,

33THEME N°2

IMPROVEMENT OF ACTORS’ SITUATIONS

In bothOuagadougouandNouakchott,the anthropologicalapproachwas the startingpointof adynamicsfor improving situationsin thewhole linewith actorsthemselves.Since1997,market-gardeninggroupsonmarket-gardeningsiteshavebeenput at thecentreofadevelopmentprocessoftheirown activities: creationor strengtheningoforganisations,prioritisation,searchofresources,supervisionof improvements,... Technologiesfor simpleprotectionofwells orfor sourceirrigation havebeenintroduced.

Socialmapsof market-gardeningsiteshavebeendevelopedby farmersandprioritisationshavebeenmadeaspart of participatoryacceleratedplanningmethod.Integrateddevelopmentprograms(from sitesto households)arebeingpresentedto variouspartnersincluding theUnitedNationsSystemfor financingmicro-projectsin orderto improvein asustainablewaythe environmentofurbanmarket-gardeningsites.

34THEME N°2

CONCLUSION

Situationsofwastewaterre-usein anunderstandingof” planned”and” controlled” typearestill veryrarein saheliancountries.In Nouakchott(Mauritania)suchsituationtype is underwayon theSebkhasite. In Ouagadougou,suchasituationhasbeenplannedaspartofPSAO;beforethis programis implemented,it is the situationsof” unplanned”and“not controlled”wastewaterre-usewhichareencountered.

In bothcases,therearepotentialrisksrelatedto wastewaterre-use(higherlevelsofbacteriologicalandparasiticalpollutionascomparedwith levels ofWHO instructions).Practiceson sites(enrichingbasinwater,walkingbare-foot,wateringwith an overcoaton, ...) increasehealthrisks. Epidemiologicalstudieshaveshownthatthereareadditionalhealthnsksfor market-gardenersandtheir children.

It’s highly importantthathealthandpublic authoritiesestablisheffectivecontrol andfollow-up programson existingsitesof unplannedwastewaterre-use.Otherwise,somefarmergroupswill continueto useraw wastewaterfor types of cropswhich arenot recommendedwhileignoring thescopeof healthrisks.

A greaterrigour is requiredin planningwastewatertreatmentsystemsdownstreamof whichwastere-usehasbeenplanned.Any future malfunctionof theSTEPwill not beknownalwaysto market-gardenerswho arestill unlikely to changefarmingpractices.

35THEME N°2

Table 1: Differencesofbacteriologicalcontamination(faecalcoliformsper 100 ml) betweenwateringwatertypeson market-gardeningsitesin Ouagadougou(resultsoftwo years’weeklyfollow-up, 1994and1995).

Sitesandwatertypes Observation(s) FecalColiforms per 100 ml * P~value**Average Median Minimum Maximum

All sites***Basinwater 72 l.lE+06 8.3E+04 5.OE+02 3.4E+07

Damwater 174 3.3E+04 4.5E+03

Siteset typesd’eau Observation(s) Coliformes Fécauxpar 100 ml * P~value**

Moyeime Médiane Minimum Maximum

Toussites***Eauxde Bassin 72 1.1E+06 8.3E+04 5.OE+02 3.4E+07

Eauxde Barrage 174 3.3E+04 4.5E+03

CONCLUSION

Danslespayssahéhens,les situationsde réutilisationdeseauxuséesdansunecomprehensionde type“planifiée “ et” controlée”sontencoretrèsrares.A Nouakchott(Mauritanie)unesituationde ce typeestencourssurle site de Sebkha.A Ouagadougou,unetelle situationestenprojet dansle cadredu PSAO ; et en attendantquece projet voit le jour , ce sontdessituationsde réutilisationdeseauxuséesdemanière“non planifiée” et “ noncontrôlée“ quisontrencontrées.

Dansun cascommedansl’autre, lesrisquespotentielslies a la réutilisationdeseauxuséesexistent(niveauxdepollutionbacteriologiqueset parasitologiquessupérieursauxseuilsdesdirectives de l’OMS). Lespratiquessurles sitesdemaraIchage(enrichissementdeseauxdesbassins,marchepiedsnus,arrosageen surverse,...)augmententles risquessanitaires.Lesetudesépidémiologiquesmontrentqu’il existeun surcroIt de risquessanitairespour lesexploitantsmaraIcherset lesenfantsdesexploitantsmaraIchers.

Ii estde la plusgrandeimportanceque les autoritéssanitaireset publiquesmettentenplacedesprogrammesefficacesde contrôleet de suivi surles sitesexistantsderéutilisationnonplanifiéedeseauxusées.Sinon,certainsgroupesd’exploitantsmaraIcherscontinuerontautiliser deseauxuséesbrutespourdestypesde culturesnonrecommandés,enméconnaissant1’ampleurdesrisquessanitaires.

Unegranderigueurestnécessairedansla plamficationdesystémesd’épurationdeseauxuséesen avaldesquelsla reutilisationdeseffluentsestprévue.Tout dysfonctionnementultérieurdela STEPneserapastoujours connudesexploitantsmaraIchers,encoremomssusceptibledechangerleurspratiquesculturales.

35THEME N°2

L’AMELIORATION DES SITUATIONS AVEC LES ACTEURS

Ajissi bienaNouakchottqu’a Ouagadougou,la demarchesocio-anthropologiquea etele point~:, de departd’unedynamiqued’améliorationdessituationsdanstoutela chaIneaveclesacteurs

eux-m~mes.LesgroupesdemaraicherssurlessitesdemaraIchageont étémis, depuis1997,an centred’un processusde développementde leurs activités: creationou renforcementd’associations,établissementdespriorités,recherchedesmoyens,conduitedesameliorations,...Destechnologiessimplesdeprotectiondespuits ou d’irrigation a la racineont étéintroduites.

Des cartessocialesdessites de maraIchage ont été élaboréesparles exploitants,et desclassificationsde prioritésont étéopéréesdansle cadredela méthodeaccéléréede planificationparticipative.Desprogrammesdedéveloppementintégré(allantdessitesauxménages)sontencoursd’être présentésa différentspartenaires,dontceuxdu SystèmedesNationsUnies,pour le financementdemicro-projets,devantaméliorerde facondurablel’environnementdes

sitesdemaraIchageurbain.

34THEME N°2

LA PLACE DES ACTEURS DANS LA PROBLEMATIQUE

Ii existed’autresétapesqui suiventcellede la productiondeslegumes(sitesdemaraIchage),tellesquela vente dansles marches,la ventedansles petits servicesde restauration,et laconsommationenpublic ou enprivé. Lesacteursconcernésparnotreproblematiquesontdonenombreux:exploitants,revendeurs,traiteurs,consommateurspublics.A traverscesdifférentsacteurs,les aspectséconomiqueset sociauxde l’activité demaraIchagesontimportants.LemaraIchage,et la disponibilitéd’eauxuséesqui le permet,procurentuneactivité et desrevenusnonnégligeablesa descentainesde famillesdanslesdeuxvilles.

Pourévaluerle role desacteursdansla chaInedesrisquessanitaires,unedémarchesocio-anthropologiqueapermis derecueillir les idéeset croyancesdes différentsacteursdanslachaInede distributiondes legumes(du producteurau consommateur),et deprocédera desobservationsdirectesdesfacteursenvironnementauxainsiquedespratiquessurles différentslieux decettechaIne.

LES CONTRAINTES TECHNOLOGIQUES

Laréutilisationplanifiéeounondeseauxusées,pourqu’elle sepratiquesansrisquessanitaires,requiertl’adoptiondesolutionstechnologiquesqui nesontpasfacilesa trouver, amettreenplace,ou a exploiter.Dansle casdessituationsde réutilisationplanifiée,les contraintestechnologiquessontrelativesauxproblèmesd’exploitationet d’entretien.Uneétudedu CIEH (CIEH, 1992)dansun certainnombredepaysafricainsamis enevidencele faiblepourcentagedestationsd’épurationayantun fonctionnementconvenable quelques annéesaprès leur mise en service.Danslescasdessituationsde réutilisationnonplanifiée,lessolutionstechniquespourréduireles pollutions sontdifficiles a mettreenplaceauprèsdesexploitants : protectiondespuits,changementdestechniquesd’irrigation

33THEME N°2

LES RISQIJESEFFECTIFS

Pourévaluerles risqueseffectifs,deux démarchesépidémiologiquesontété combinées:l’approche”exposés(contre)nonexposés“, et l’approche“ cas(contre)témoins“.A Ouagadougou,l’étude de type “ exposés- nonexposés“, ciblantles enfants,conduiteen1995 (Cissé, 1997), montre que les enfantsd’exploitantsmaraIchersâgés de momsde 5 ans présentent,de manière significative, des prévalencessupérieuresa cellesdes enfants du méme age de la population générale pour les Ankylostomes(10.80±6.68%contre1.40±0.43%,RP = 8.45,p

LES RISQUIES POTENTIELS

Pour évaluerles risquespotentiels,deux démarchesont ete combinées : une démarchecartographiqueet unedémarchemicrobiologique.

La démarchecartographique,aidéeparla géomatique,apermis(i)- decaracteriserlessecteursde residencede la ville selonla pollution parlesdépôtsd’ordureset lesrejetsd’eauxusées,(ii)- depositionnerlessitesdemaraIchagedansle tissuurbain,et(iii)- d’évaluerl’importancedessuperficiesexploitéesen saisonsèche,saisonfraIcheet saisondespluies.La démarchemicrobiologiquea permis de suivre la pollution bactériologique(coliformesfécaux)etparasitologique (oeufs d’helminthes et protozoaires) des eaux, des sols,et des végétaux.AOuagadougou, le suivi pendant deux années consécutives des types d’eaux d’arrosage utiliséssur 4 principales zones de maraIchagede Ouagadougou(Abattoir, Canalcentral,Tanghin,Boulmougou)a montréquetousles types d’eau,mêmeles eaux de puits, présententtinepollutionbactériologiquequi dépassegénéralementles seuilsrecommandésparl’OMS pourl’arrosagede legumessusceptiblesd’être consomméscrus(Tableau1). Leseauxderigoleset de canauxouvertsprésententles niveaux de pollutions les plus importants(médianesrespectives5.9 l0~,et 1.4 106, maximum respectifs 2.2 i07 et 9.4 10~),voisinsde niveauxd’eauxuséesbrutes.Elles s’avèrentdonelesplusdangereusespourla sante,particulièrementen regarddesrésultatsparasitologiques(Figure 1). LessitesdemaraIchageseformantautourde cestypesd’eaux (parexemple,Abattoir et Canalcentral)présententainsi les plusfortspotentielsde risquessanitairespourlesexploitantsmaraIcherset leurfamille (Cissé,1997).

A Nouakchott,lesanalysesdeseauxuséesépuréessortantde Ia STEPont trouvéun niveaudepollutionbactériologiqueconformeauxdirectivesde 1’OMS (Schneideret Gagneux,1997).Parcontre, les niveauxde pollution des eauxdanslesbassinsd’arrosagedesexploitantsprésententunemédianede 9.1 104 CF/100ml. L’augmentationdespollutionsdanslesbassinsseraitdueaunepratique,largementrépanduesurles sitesdeNouakchott,consistanta enrichirleseauxdubassineny versantdessacsde fumier avicole.

31THEME N°.2

rSituation a Ouagadougou

L ~A Ouagadougou,il n’y apasde réseaupublic de collectedeseauxuséesversuneSTEP.Iiexistetine stationd’épurationparbouesactivéespourleseauxuséesdu marchécentral,miseenplaceen 1988. Dansuneétudefaite quelquesannéesseulementaprèsla miseenservicede la STEPdu marché,la qualitédeseauxa la sortiede la STEPdépassaitdéjàde loin lesnonnesde rejetsprévuesparle cahierde charge(CREPA, 1991).

Leseffluentsde cettestationsontdéversésdansun canala ciel ouvertqui débouchedanslazonede la forêt classée,oü les eauxrejoignentd’autreseauxd’un réseauhydrographiqueconvergenta cet endroit.En cet endroit(bas-fonds)deconvergenced’eauxde ruissellement,débouchentégalementleseauxuséesenprovenancedela zoneindustriellede Kossodo(Abattoir,SOBBRA,TanAliz). Une importanteactivité de maraIchageserencontredanscettezonedebas-fonds, autour d’eaux polluées coulant dans les rigoles (Cissé, 1997).L’activité demaraIchagea Ouagadougouserencontregénéralementautourd’eaudebarrage,et d’eaudepuits, maisaussi,dansbeaucoupde cas,autourde rejetsd’eauxuséesqu’on trouvethnsdescanauxet desrigoles (Abattoir, SO.B.BRA,Tannerie,Canalcentral,Kossodo).Onpentcompter48 endroitsoü les sitesde maraIchageapparaissentoccasionnellementou demanièrepermanentedansl’année (voir la position géographiquede cessites danslaFigure2).Leseauxutiliséessurceszonesproviennentdespuits,desbarrages,desrigoles,desmarigots,ou des canaux ouverts d’assainissement pluvial.

Ii estprévu,dansle Plan Stratégiqued’Assainissementde Ia ville de Ouagadougou (PSAO),la réahsationd’un réseaud’assainissementde typecollectifcomportantla collecteet l’épurationdes eauxuséesurbaineset des effluentsindustriels(ONEA, 1993). Ceréseaucollectifneconcerneraque, d’unepart, lessecteursdont l’urbanisationestsuffisammentdense,et, d’autrepart,les établissementsgrosproducteursd’eauxusées.Leseauxuseesserontévacuéesverstine stationd’épurationparlagunagedansle bas-fonddeKossodo,oü leur réutilisationparlesexploitantsmaraIchersde cesite estprévue.

Ii s’agitdone, a Ouagadougou,d’une situationderéutilisationdeseauxuséesactuellementnonvoulue (“ situationnonplanifiée “), donton n’assurepasencorele contrôle(“ situationnon contrôlée “), et qui devrait connaItre une evolution, avec le PSAO, vers une situation voulue(“ situationplanifiée “) et qui devrait être “ contrôlée “.

30THEME N°.2

Plusieursméthodeset outils ont ete utilisés,notanimentun appareilGPS(GeoPositioningSystem).Les donnéescollectéesparl’appareilGPSdeGarminont étéconvertiesa l’aide dulogiciel PCX5 de Garmin, et traitéesavec le logiciel Excel. Parailleurs, une enquêteépidémiologiquecouvrantles 30 secteursde la ville aportestir les diarrhéeschezlesenfantsde momsde 5 ans.Les données collectées par les enquêteursont été saisiessur plusieurslogicielsselonle formulaireutilisé: logiciel EPIINFOpourles questionnaires;logiciel Excelpourles formulairesd’enquêtegéographique.La cartede basede Ouagadougoua l’échelle1/10.000aéténumérisée,ainsiquelescartesthématiques.Les synthesesdesbasesde domiéeset la presentationdesrésultats~ l’échelle du secteuront été effectuéesa l’aide du logicielMapinfo.

Ladémarchegéomatiqueaperrnis(i)- decaractériserlessecteursderesidencedeOuagadougouselon la pollution par lesdepOtsd’ordureset lesrejets d’eauxusées,(ii)- depositionnerlessitesdemaraIchagedansle tissuurbain,et (iii)- d’évaluerl’importancedessuperficiesexploitéesensaisonsèche,saisonfraIcheet saisondespluies.

Ladémarchegéomatiqueapermis,aussi,dedésagrégerlesprincipauxrésultatsde la démarcheépidémiologiquepourlespresentera l’échelle du secteur,sousformedecartesthematiques.

LES SITES DE MARAICHAGE DANS LE TISSU UREATh~

Situation a Nouakchott

A Nouakchott,onpetit compter7 sitesdemaraIchagemajeurs(Schneideret Gagneux,1997).Le site de Sebkha,situéaucentreville, constituele plusancienpérimètremaraicher,créédansle cadrede la miseenserviced’une stationd’épuration(STEP)deseauxuséesen 1965. Lastationd’épurationétaitde type lit bactérien,dont l’effluent alimentaitunréseaudedistributiondeseuxépuréesde Ia STEP,mis en place pour 72parcelles(Ould Baba,1999).Lesproblèmesd’exploitationont conduita unedegradationcontinuelledescapacitésépuratoires,jusqu’àl’arrêt completde la stationen1979. Cet arrêtd’épurationn’a pasempêchéquel’arrivée deseauxusées,non épurées,continuestir les sites de maraIchage,malgréun certainnombred’étudesalertantstir lesrisquessanitaires(Sidatt, 1979 ; Sidatt, 1982). Un programmederehabilitation, lance en 1990 avecl’aide de la BAD (CIEH, 1992),aabouti en 1992 aveclamiseen serviced’une stationd’épurationè~bouesactivées.Les eauxuséessubissentuntraitementtertiairepar chloration,avantd’être évacuéesversle réseaude distributionsur lesite demaraIchage.Le contrOledeseauxuséess’opèreuniquementpourlesparamètresphysico-chimiques; parcontre,lespollutionsbactériologiqueset parasitologiques(preoccupationsdesdirectivesde l’OMS) ne font pasl’objet d’analyses.Ii s’agit done, aNouakchott,d’unesituationde réutilisationdeseauxuséesvoulue(“ situationplanifiée “), dont on a perdu le contrôle de 1979 a 1992 (“ situation non contrôlée “), et quiredevientnormaleaprèsla rehabilitationdepuis1992 (“ situation contrôlée “, mêmesi cecontrôleestlimité encore).

29THEME N°2

PROBLEMATIQUEGENERALE

Risquessanitaires lies a la réutilisation deseaux usées

Ii existe4categoriesdepersonnessurqui l’utilisation agricoledeseauxrésiduairesfait peserun risque“potentiel” distinctdu risque“effectif’ (Maraet al., 1992):(i)- les ouvriersagncolestravaillantdansles champset les membresde leur famille; (ii) les manutentionnairesetmanipulateursdesproduits desrécoltes;(iii) les consommateursdes cultures(honimesetbétail); (iv)- lespersonnesvivant a proximité deschamps.

Directives de L’OMS en matière de réutilisation deseauxusées

Lesprincipauxélémentsdesrecornmandationsde l’OMS (OMS, 1989)sont: (i)- l’utilisationd’effluentbrut doit êtreproscriteen toute circonstance;(ii)- leseauxutiliséesdoivent, en toutcas,contenirmomsd’un oeufdeparasiteintestinalenmoyennearithmétiqueparlitre; c’estlà l’une desprincipalesexigencesnouvelles,qui vadansle sensdu renforcementdesnormes;(iii)- la qualitémicrobiologiquedeseauxdoit êtresurveilléedansle casde legumesa mangerems,d’irrigation d’espacesrécréatifset lorsqu’uneméthoded’aspersionestutilisée; ceseauxdoiventcontenirmomsde 1 ~ coliformesfécauxparlitre; (iv)- unenormeplus stricte, inférieureadeuxmille coliformesfécauxparlitre, seraappliquéeauxgazons,commeceuxd’hôtels,aveclesquelsle public estdirectementencontact.

Nécessitéd’une approche multidisciplinaire

Dansl’évaluationdesrisquessanitaireslies auxeauxuséesdansdeuxpayssahéliens,le projetderechercheacombine,dansuneapprochetransdisciplinaire,la cartographie(positionnementspatialdesphénomènesenvironnementaux),la microbiologie(evaluationdesrisquespotentiels),la sociologicet Panthropologie(eclairagedesfacteursde risque),l’epidémiologie(evaluationdes risques effectifs), et la géomatique (analyse de la dimension spatiale).

L’approche géomatique

Lesfacteursenvironnementauxenmilieu urbainétantparticulièrementlocalisés,Ta géomatiqueestaujourd’huiunedisciplineincontournablepourunemeilleuregestiondesenvironnements

urbains.Dansle cadredecetteétude,l’approchegéomatiqueaoccupétin placeprimordiale.Une enquêtegéographiqueexhaustivedansles 30 secteursde la ville de Ouagadougoua etéconduite, relative aux sites de maraIchage,aux eauxuséeset aux déchetssolides.

28THEME N°2

INTRODUCTION

Des quel’on évoque“ Ia réutilisationdeseauxusées“, le senscommunventquesoit sous-entendu”choixplanifié et contrôlé“. Danscettecomprehension,lesquestionscourantessont,entreautres: quellessontlestechniquesd’épurationlesplusindiquéespourrendrela réutilisationdeseauxuséespossible? Quellessontlesnormesquedeseauxuséesdoiventrespecterpourleur réutilisationsansrisque?Quellessontlesmesuresit prendre pour assurerle contrOledesperformancesdessystèmesd’épurationmis enplace?Or, dansbeaucoupde paysenAfrique, la réutilisationdeseauxuséesserencontresansquecela soit consécutifii uneplanificationvoulue, et sansaucunmécanismede contrôlede Taqualité deseauxutiliséespourl’arrosagedelegumes,mêmesi ceuxci sontsouventconsommablescrus.L’explosiondémographiqueet l’extensionfulgurantedes villes africaines, notamment dansleszonespériurbaines,ainsiquel’urbamsationprovoquentun accroissementrapidede la demandeen eau (Coulibaly, 1998).Ce qui entraIneuneproductiondeplusenplus importanted’eauxuséesquele deficit en infrastructuresd’assainissementabandonnedanslesrues,les rigoleset les canaux.Danslespayssahéliens,le maraIchageestcourammentpratiquéenmilieu urbainetpériurbain.Selonun certainnombred’étudeseffectuéescesdernièresannées,environ200 millionsd’habitantsdevilles despaysendéveloppementsontaujourd’huidesagriculteursurbains.Lesexploitantsagricolesen milieu urbainutilisentdifférentessourcesd’ eauxpour1’ arrosagedeleurs legumes: eauxde puits, eauxde retenuedebarrages,et eauxcoulantdansdesrigoleset descanauxdedrainage.Lesconditionsde raretéde l’eausurles sitesdemaraIchage,dansdes zones arides, fontquel’on peuty rencontrerdescasextremes: certainssitesutilisent deseaux usées non traitées,coulantdansles rigoles ou canauxd’évacuationd’eauxpluvialcs,pouvant provenir aussi bien des ménages que d’industries.Dansles regionsarideset semi-arides,Ta réutilisationdes eaux usées pour l’irrigation est trèslargementpratiquée(Blumenthalet al., 1989; Strausset Blumenthal,1990;Hispanhol,1990).La pratiquede Ta réutilisationdeseauxuséesestd’ailleurs largementrépanduedansd’autresregionsdu monde;elle existe aussibien dansdespaysdéveloppésquedansdespaysendéveloppement.Certainsauteurstrouventmêmeque“l’eau estuneressourcetroprarepourn’être utiliséequ’unefois avantd’être renduea la nature...”(SandbergH., 1992). Cependant,c’estseulementdepuisquelquesannéesquela réutilisationdeseauxuséesestdevenue unsujet d’intérét scientifique,sociologiqueet économiquedanslesdiscussionssurle conceptdela gestionintégréedesressources en eau. Certainspaysafricains,commela Turiisie et l’Afriquedu Sud,,ont fait de Ia réutilisationdeseauxuséestine prioriténationale(LeVine Renaud,1998).Jusqu’àtine périoderécente,l’on disposaitdepeud’étudesstir la réutilisationdeseauxuséesdanslespayssahéliens.Depuis 1994, l’Ecole Inter Etatsd’Ingénieursde l’EquipementRural(EIER), enpartenariatavecl’Ecole PolytechniqueFédéralede Lausanne(EPFL), et 1’InstitutTropical Suisse(ITS), conduitdestravauxde recherchemultidisciplinairesurTa réutilisationdeseauxuséesenmaraIchageurbaindansdeuxpayssahéliens,avecnotammentuneperspectiveépidémiologique,associéeit Ta microbiologic, la socio-anthropologie,la cartographic,et lagéomatique.Intérêtéconomiqueet socialde l’agricultureurbaine,existencedenombreuxfaits accomplisd’utilisation d’eaux polluéespar despopulationspenconscientesdes risquessanitaires,faiblessedesinstitutionspubliquessusceptiblesde fairerespecterdesdirectives sanitaires, oude mettre en placedes ouvragesde traitementcollectif des eauxusées,nécessitépour Tesscientifiquesdecontribuera Ta recherchedessolutionsqui améliorentlessituationsavecTesacteurseuxmêmes: tels sontlesprincipauxenjeux.

27THEME N°2

lOème CONGRES UADE, DURBAN,AFRIQUE DU SUP(19-25fevrier 2000)

Theme: Réutilisationdeseauxuséesetdessous-produitsd’épurationenAfrique

REUTILISATION DES EAUX USEESEN AGRICULTURE

URBAINE DANS LE CONTEXTE SAHELIEN

RISQUES SANITAIRES, ASPECTSECONOMIQUES,

ET CONTRAINTES TECHNOLOGIQUES.Dr. CISSEGuéladio,EIER, Ouagadougou,BurkinaFaso

RESUME

Dansleszonesandes,enparticulier au Sahel,la limitation desressourceseneaufait de la

réutilisationdeseauxuséesunecomposanteincontournablede la gestionintégréedesressourceseneau.Lapratiquederéutilisationde toutessortesd’eauxuséess‘y renconfredemanière nonplanzfiéeet non contrdlée danslesactivitésd’agricultureurbaine.

Intérétéconomiqueetsocialde 1 ‘agriculture urbaine,existencedenombreuxfaitsaccomplisd’utilisation d’eauxpolluéespar despopulationspeu conscientesdesrisquessanitaires,

faiblessedesinstitutionspubliquessusceptiblesdefairerespecterdesdirectivessanitaires,oudemettreenplacedesouvragesde traitementcollectifdeseaux usées,nécessitépour les

scientijiquesdecontribuer a la recherchedessolutionsqui améliorentlessituationsaveclesacteurseuxmêmes,telssontlesprincipauxenjeux.

Jusqu‘a unepérioderécente,1 ‘on disposaitdepeud‘etudessur la réutilisationdeseauxuséesdanslespayssahéliens.Depuis1994, 1 ‘EcoleInter Etatsd‘Ingénieursde 1 ‘EquipementRural(EIER),enpartenariatavec1 ‘Ecole PolytechniqueFédéraledeLausanne(EPFL), et1 ‘Institut

Tropical Suisse(ITS), conduitdestravauxde recherchemultidisciplinairesur la réutilisation

deseauxuséesenmaraIchageurbaindanslespayssahéliens,avecnotammentuneperspective

épidémiologique,associéea la microbiologie, la socio-anthropologie,la cartographie,et lagéomatique.

Leprogrammede recherchea pris commepoint de depart la problématiquedesrisquessanitaireslies a l’utilisation d’eauxpolluéesen maraIchageurbain, danslesconditionsd’ariditédevilles sahéliennes,pour aboutira la miseenplacedeprocessusinteractifsdedéveloppementdurableau niveaulocal, depuis1997.

L’articleprésentelesenseignementstires deceprogrammederecherchesurplusieursannées,pourcontribuera la nécessitédepoursuivreetdevulgariserlesconnaissancesdanscedomaine.

Mots des : Sahel,maraIchageurbain, réutilisationdeseauxusées,impactssanitaires,gestionintégrée,développementparticipatifau niveaulocal.

26THEME N°2

THEME N°.2

REUTILISATION DES EAUXUSEES ET DE LEURS SOUS

PRODUITS

Par CisséGUELADIO (EJER)

La technologied’épurationde pointe en matièrede lagunagede cette STEPnouvellementintroduite an Maroc a permis d’atteindreles objectifs fixes qui sont Ta protectiondel’environnementet le dégagementd’uneressourcehydriquesupplémentairede qualitéconformea tine rëutilisationpour l’irrigation desespacesverts. Cetteactions’adapteparfaitementanotrecontextesocio-économiqueet ouvredenouveauxhorizonsdansle domainederéutilisationdeseauxdansnotrepays.La généralisationdeprojetssimilairesauxmoyensetpetits centrespourraitreprésenterunebonnealternativedegestionet derécupérationdeseauxsurtoutdanslesconditionsde raretédesressourceseneau.

REFERENCES

1- Conseil Supérieur de l’Eau et du Climat du Royaumedu Maroc. (1993)RéutilisationdeseauxuséesenAgriculture ~èmeSession.

2- Ministère de l’Agriculture et de la Mise en Valeur Agricole du Royaumedu Maroc.(1994)Réutilisationdeseauxuséesa desfins agricoles.Projet M0R86/018PNTJD,FAO. OMS.Janvier1994.

3- Kawni.A et J. Darley.(1996)La réutilisationagricoledeseauxuséesépuréesau Maroc.Direction de l’Eau et de l’Assainissementde la DGCL (Ministèrede l’intérieur duRoyaumeduMaroc). Décembre1996.

4- I.A.V. HassanII., ORMVA/soussMassaet RAMSA. (1996)Epurationdeseauxuséeset leurvalorisationdansl’agriculture . Casde la communeurbainedeBenSergao,Wilayad’ Agadir.

5- Municipalité de Ben Slimanedu Royaumedu Maroc., TAIIAL consulting engineersLTD., MILDEAS et ONEP. (1997) Stationd’épuration et de recyclagedeseauxuséesde BenSlimane.Manueld’exploitation..Juin 1997.

6- CEE. (1991)Directivesdu Conseildu 21 mai 1991 relativesautraitementdeseauxurbainesrésiduaires.Journalofficiel descommunautéseuropéennes.

7- ONEP-GTZ. (1998)Typologiedeseauxuséesurbainesau Maroc.Cooperationtechniquemaroco-allemande,juin 1998.

8- Echihabi. L.,A. Foutlane.,A. Yagoubi., J. Bahij.,A. Maghrabi.,Y. Loulidi etA. Lahlou.(1999) Evaluationdesperformancesépuratoiresde Ta stationd’épurationdeseauxuséesde la yule de BenShmaneau Maroc- TypeLagunage-

9 - Prost.A. (1987)Lesdangersdemaladiesinfectieuseslies a la réutilisationdeseauxusées.Bulletin dequalitédeseaux,OMS,juin 1987.

10- Saenz.R (1987) Irrigation avecdeseauxuséesépuréesenétangsdestabilisation—Evaluation des aspectsmicrobiologiques.Bulletin dequalite deseaux,OMS,juin 1987.

11- World Health Organization. (1989) Health guidelines for theuse of wastewater inagncultureandaquaculture.Report ofaWHO scientificGroup.TechnicalReportSeries778. Geneva,l989.

24

THEME N°2

Evaluation descoüts

Coüt d’investissement

Le coütd’investissementde la Stationd’épurationdeseauxuséesde la ville de BenSlimane,réaliséeen 1997,estde96,44millions dedirhams*.

*lDirhams(DH) = 0,104Dollars US

Coüt d’exploitation

L’évaluation desfrais d’exploitationde la stationd’épurationeffectuéedurant1998estdétailléedansle tableau2 ci-après.

Tableau 2. Frais d’exploitation annuellesde la STEP deBen Slimane(juillet 1997-juin 1998)

LIBELLE FRAIS (DHIan)PERSONNEL 589255ENERGIE 196045LABORATOIRE 24000ENTRETIENMECANIQUE 20410NETTOYAGE 15200DIVERS 90 874

Total 935 784

Coüt de revient

Le coüt de revient de la production des eaux uséesépuréesest de 1,45 DH/m3.

Ainsi en considérantle prix actuelde ventedes eauxuséesépuréeset qui estde l’ordre de2DHIm3, il ressortquecetteoperationestrentablepourle gestionnairede la station.Parailleurs,lesgains sontaussinota