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Martin SEIDLLEESU ENPC Université Paris-Est OPED v 2018

Eaux usées,concepts de traitementadaptés au pays du Sud

2

Assainissement dans le monde

UNEP/GRID-Arendal

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Usages : les ménages en France

44

50%20%

10%

20%

showerwashingdishescooking

Production 50 - 60 L/ cap/ day

SOURCE :Yamoussoukro, Seidl et al 2005

Usages : les ménages en Afrique

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Flow analysis for waste water within a household of Yamoussoukro. The amounts are given in litre a day a capita.

HOUSEHOLD

process unit

22.7 (septic) tanksto be treated

8.4 gully to be treated

8.7 soaking pits, infiltration

13.8 thrown out in or outside the yard evaporation

tap water outside, resellers

6.4

tap water inside 40.4

well water 6.4

SOURCE :Yamoussoukro, Seidl et al 2005

Usages : les ménages

6

« Drainage »

Ouahigouya, Burkina Faso

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Variation jour /nuit des flux

88

Yellow water (urine)

Brown water (faeces + flush

water)

Black water (from toilets)

Domestic wastewater

Grey water

Sullage

Composition des flux

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Litres per person per year:

1. Brown water: ~502. Yellow water: ~5003. Grey water: ~10,000–100,000

– ie, domestic wastewater volume of ~30–275 litres per person per day

Possibilité du traitement partiel

ENJEUX : • diminuer volumes• récupérer N,P

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Réutilisation, concept ECOSAN

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Traitement séparé des flux

1212

USA ~70 g BOD/person /dayCEE ~60 g BOD/person /day = rural ~50 g BOD/person /day

Developing ~40 g BOD/person /daycountries

Charge à traiter

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Les objectifs d’assainissement

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« Interface utilisateur »

collecte

Problème et résolution

TRAITMENT

rejets

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Priorités du traitement

Élimination (dans l’ordre d’importance) des1. pathogènes2. matières organiques3. nutriments4. micropolluants

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Concepts de traitements

TreatmentPhysico-chemical / biologicalAerobic / anaerobiccPrimary /secondary / tertiaryIntensive / extensive – conventional / naturalCollective / on-siteTreatment chain

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Physico-chimique / biologique

Il existe deux techniques principales pour épurer les eaux, s'appliquant tant au traitement des eaux usées qu'à la production d'eau potable, les techniques physico-chimiques et les techniques biologiques.

Physico-chimiques : sédimentation/ flottation, filtration, floculationBiologique : bactéries, champignons, protozoaires, Lumbricidae, algae, macrophytes

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Aérobie / anaérobie

Il existe deux conditions principales pour la dégradation de la matière organique :

aérobie : présence d’O2 , déchets CO2 + H2Onitrification : présence d’O2 , NH4 NO3

anaérobie : absence d’O2 , déchets CO2 + CH4 / H2

dénitrification : absence d’O2 , NO3 N2

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Primaire - tertiaire

2020

Traitement : chaine des procédées

screening

grid removal

settler

Primary production

Organic matter removal

Organic matter removalO2

Separation solid/ liquid /gaz

? ? ?

treatment SYSTEM

treatment PROCESS

N/P removal

disinfection

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wikiIntensif

Extensif

22

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Le système

MENAGE

QUARTIER

VILLE

isoler

ÉvacuerTraiter

CollecterTraiter

latrine

latrineVidangeur

STEP

ÉgoutsSTEP

24Agnes Montangero SANDEC 2004

Le mix

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Choix technologique

0

100

spac

e

cons

truct

ion

man

egem

ent

tech

nics

effic

ienc

y

envi

ron.

developingindustrialised

important

The choice of technology for centralised wastewater treatment, is dependent of the socio-economic status of the society. The priority is rarely the same

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Les choix

Processes ► Systems ▼

surface m²/EH

(France) sedime-tation

filtra- tion digestion

primary produc-

tion nitri-

fication denitri- fication

WSP + aerated ±5 + - anaerobic

+ aerobic + + +

WSP 11 + - anaerobic + aerobic + + +

Settler-digester and percolation 1.5 + - anaerobic - - -

UASB 1 + - anaerobic - - - Filtres with

macrophytes 2.5 - + aerobic - / + + -

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UN

EP

-International Environm

ental Technology C

entre: United N

ations Environm

ent Program

me

Advantages and Disadvantages of Conventional and Non-conventional Wastewater Treatment Technologies.

Treatment type Advantages Disadvantages

Stabilization lagoonsLow capital cost, low operation and maintenance costs, low technical manpower requirement

Requires a large area of land, may produce undesirable odors

Aerated lagoons Requires relatively little land area, produces few undesirable odors

Requires mechanical devices to aerate the basins, produces effluents with a high suspended solids concentration

Septic tanksCan be used by individual households, easy to operate and maintain, can be built in rural areas

Provides a low treatment efficiency, must be pumped occasionally, requires a landfill for periodic disposal of sludge and septage

Constructed wetlandsRemoves up to 70 % of solids and bacteria, minimal capital cost, low operation and maintenance requirements and costs

Remains largely experimental, requires periodic removal of excess plant material, best used in areas where suitable native plants are available

Filtration systemsMinimal land requirements, can be used for household-scale treatment, relatively low cost, easy to operate

Requires mechanical devices

Vertical biological reactors

Highly efficient treatment method, requires little land area, applicable to small communities for local-scale treatment and to big cities for regional-scale treatment

High cost, complex technology, requires technically skilled manpower for operation and maintenance, needs spare-parts-availability, has a high energy requirement

Activated sludge

Highly efficient treatment method, requires little land area, applicable to small communities for local-scale treatment and to big cities for regional-scale treatment

High cost, requires sludge disposal area (sludge is usually land-spread), requires technically skilled manpower for operation and maintenance

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Choix entre emprise au sol et coûts énergétiques

Argent dépensé pour l’achat d’un terrain est un investissement

Argent dépensé en énergie sont des coûts de fonctionnement

Naturel vs conventionnel

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Pays en développement

Assainissement< 20 % Collectif> 80% Autonome

Assainissement collectif80% séparatif20% unitaire

Choix individuel / collective

tradit.50%

VIP10%

Tanks26%

Nature9%

WWTP5%

tradit.VIPTanksNatureWWTP

Ouagadougou Burkina

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Choix

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Références