11

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

3

Eau usée

44

Usages : les ménages

55

Eau usée~ Eau potable

66

50%20%

10%

20%

showerwashingdishescooking

Production 50 - 60 L/ cap/ day

SOURCE :Yamoussoukro, Seidl et al 2005

Usages : les ménages

77

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

8

« Drainage »

Ouahigouya, Burkina Faso

99

Variation jour /nuit des flux

1010

Yellow water (urine)

Brown water (faeces + flush

water)

Black water (from toilets)

Domestic wastewater

Grey water

Sullage

Composition des flux

1111

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

12

Réutilisation, concept ECOSAN

13

Traitement séparé des flux

1414

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

15

Traitement

16

« Interface utilisateur »

collecte

Problème et résolution

TRAITMENT

rejets

17

Les objectifs d’assainissement

1818

Priorités du traitement

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

19

Le système

2020

Concepts de traitements

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

2121

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

2222

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

2323

Primaire - tertiaire

2424

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

2525

wikiIntensif

26Agnes Montangero SANDEC 2004

Le mix

2727

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

2828

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 - / + + -

29

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

30

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

3131

DEVELOPING COUNTRIES

Sanitation< 20 % Collective> 80% Individual

Collective sanitation80% separative20% unitary

Choix individuel / collective

tradit.50%

VIP10%

Tanks26%

Nature9%

WWTP5%

tradit.VIPTanksNatureWWTP

Ouagadougou Burkina

32

Choix

33

Références