Eaux usées concepts de traitement

Transcription

1 Eaux usées concepts de traitement Martin SEIDL LEESU ENPC Université Paris-Est V Sanitation in the world UNEP/GRID-Arendal 2

2 Problème et résolution Interface utilisateur collecte TRAITMENT Rejets 3 Les objectifs d assainissement 4

3 Priorités du traitement Élimination (dans l ordre d importance) des 1. pathogènes 2. matières organiques 3. nutriments 4. micropolluants 5 Choice of technology 100 important developing industrialised The choice of technology for centralised wastewater treatment, is dependent of the socio-economic status of the society. The priority is rarely the same 0 space construction manegement technics efficiency environ. 6

4 Le système 7 Definitions Treatment Physico-chemical / biological Aerobic / anaerobicc Primary /secondary / tertiary Intensive / extensive conventional / natural Collective / on-site Treatment chain 8

5 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, floculation Biologique : bactéries, champignons, protozoaires, Lumbricidae, algae, macrophytes 9 Aérobie / anaérobie Il existe deux conditions principales pour la dégradation de la matière organique : aérobie : présence d O 2, déchets CO 2 + H 2 O nitrification : présence d O 2, NH 4 NO 3 anaérobie : absence d O 2, déchets CO 2 + CH 4 / H 2 dénitrification : absence d O 2, NO 3 N 2 10

6 Primaire - tertiaire 11 Treatement chain screening treatment PROCESS grid removal settler treatment SYSTEM Organic matter removal O2 Organic matter removal??? N/P removal Primary production Separation solid/ liquid /gaz disinfection 12

7 Intensif wiki 13 Extensive 14

8 The reality : mix of faecal sludge and wastewater Agnes Montangero SANDEC Advantages and Disadvantages of Conventional and Nonconventional Wastewater Treatment Technologies. Treatment type Stabilization lagoons Aerated lagoons Septic tanks Constructed wetlands Filtration systems Vertical biological reactors Activated sludge Advantages Low capital cost, low operation and maintenance costs, low technical manpower requirement Requires relatively little land area, produces few undesirable odors Can be used by individual households, easy to operate and maintain, can be built in rural areas Removes up to 70 % of solids and bacteria, minimal capital cost, low operation and maintenance requirements and costs Minimal land requirements, can be used for household-scale treatment, relatively low cost, easy to operate Highly efficient treatment method, requires little land area, applicable to small communities for local-scale treatment and to big cities for regionalscale treatment Highly efficient treatment method, requires little land area, applicable to small communities for local-scale treatment and to big cities for regionalscale treatment Disadvantages Requires a large area of land, may produce undesirable odors Requires mechanical devices to aerate the basins, produces effluents with a high suspended solids concentration Provides a low treatment efficiency, must be pumped occasionally, requires a landfill for periodic disposal of sludge and septage Remains largely experimental, requires periodic removal of excess plant material, best used in areas where suitable native plants are available Requires mechanical devices High cost, complex technology, requires technically skilled manpower for operation and maintenance, needs spare-parts-availability, has a high energy requirement High cost, requires sludge disposal area (sludge is usually land-spread), requires technically skilled manpower for operation and maintenance UNEP - International Environmental Technology Centre: United Nations Environment Programme 16

9 Working systems Processes Systems surface m²/eh (France) sedimetation filtration digestion primary production nitrification denitrification WSP + aerated ±5 + - anaerobic + aerobic WSP anaerobic + aerobic Settler-digester and percolation anaerobic UASB anaerobic Filtres with macrophytes aerobic - / SAGE Natural vs Conventional Basically a choice between LAND and ELECTRICITY (energy): Money spent on land is an investment Money spent on electricity is NO investment 18

10 Choice individual / collective DEVELOPING COUNTRIES Sanitation < 20 % Collective > 80% Individual Collective sanitation 80% separative 20% unitary Tanks 26% Nature 9% WWTP 5% Ouagadougou Burkina tradit. 50% tradit. VIP Tanks Nature WWTP VIP 10% 19 Choix 20

11 Références 21