assainissement dans le monde - leesu.fr file1 martin seidl leesu enpc université paris-est oped v...
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Martin SEIDLLEESU ENPC Université Paris-Est OPED v 2018
Eaux usées,concepts de traitementadaptés au pays du Sud
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Assainissement dans le monde
UNEP/GRID-Arendal
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Eau usée~ Eau potable
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50%20%
10%
20%
showerwashingdishescooking
Production 50 - 60 L/ cap/ day
SOURCE :Yamoussoukro, Seidl et al 2005
Usages : les ménages
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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
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« Drainage »
Ouahigouya, Burkina Faso
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Variation jour /nuit des flux
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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
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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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Priorités du traitement
Élimination (dans l’ordre d’importance) des1. pathogènes2. matières organiques3. nutriments4. micropolluants
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Le système
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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
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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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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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Basically a choice between LAND and ELECTRICITY (energy):
Money spent on land is an investment Money spent on electricity is NO investment
Naturel vs conventionnel
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DEVELOPING COUNTRIES
Sanitation< 20 % Collective> 80% Individual
Collective sanitation80% separative20% unitary
Choix individuel / collective
tradit.50%
VIP10%
Tanks26%
Nature9%
WWTP5%
tradit.VIPTanksNatureWWTP
Ouagadougou Burkina
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Choix