1.2 Coordonnées des personnes-ressources et des institutions impliquées dans l'évaluation et la documentation de la Technologie

Nom du projet qui a facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Book project: where people and their land are safer - A Compendium of Good Practices in Disaster Risk Reduction (DRR) (where people and their land are safer)

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Terre des Hommes (Terre des Hommes) - Suisse

1.3 Conditions relatives à l'utilisation par WOCAT des données documentées

Le compilateur et la(les) personne(s) ressource(s) acceptent les conditions relatives à l'utilisation par WOCAT des données documentées:

Oui

1.4 Déclaration sur la durabilité de la Technologie décrite

Est-ce que la Technologie décrite ici pose problème par rapport à la dégradation des terres, de telle sorte qu'elle ne peut pas être déclarée comme étant une technologie de gestion durable des terres?

Non

2.1 Courte description de la Technologie

Définition de la Technologie:

The combination of pond sand filters (PSF) and raised pond embankments protect drinking water sources and increase the resilience to flood and tidal surge events in low-lying coastal areas.

2.2 Description détaillée de la Technologie

Description:

Coastal areas along the Bay of Bengal experience extreme seasonal variance in the presence of surface water including flooding, tidal surge, and drought. Many families living in these rural communities construct small ponds to ensure water availability for a variety of uses, such as washing, bathing, fish farming and animal watering as well as domestic use. Some families build larger ponds that are open to the use of all community members; whereby water is carried by women and children to households. Use of pond surface water may last up to several months during the year depending on the location, seasonal weather patterns, geologic conditions, capacity of the pond and user habits. Residents rely on ponds as a source of drinking water during the dry season when household rainwater harvesting techniques are no longer viable, making treatment essential.

Pond sand filters (PSF) is acentralised or semi-centralised water treatment technology often employed in many coastal areas where surface water is the only option due to saline aquifers and lack of resources for more robust, safely managed community water supply systems. The technology uses slow-sand filtration to remove turbidity (sediments) and pathogenic organisms whereby freshwater flows through layers of sand and gravel populated by a thin layer of microorganisms and treatment happens through physical and biological processes. Due to resource constraints, the number of PSF serving as water sources is usually limited. The technology considerably reduces the risk of infection with enteric pathogens. In conjunction with PSF, safe water transport (covered and cleaned containers) and household water treatment systems (chemical or additional filtration devices) are essential.
As stated in the Sustainable Sanitation and Water Management Toolbox (SSWM) slow sand filtration systems are characterised by a high reliability and rather low lifecycle costs. Moreover, neither construction nor operation and maintenance require more than basic skills. Hence, slow sand filtration is a promising filtration method for small to medium-sized, rural communities with a fairly good quality of the initial surface water source. As stated by the the World Health Organisation, slow sand filtration provides a simple but highly effective and considerably cheap tool that can contribute to a sustainable water management system.
Once a SSF facility is built, only clean sand is required for occasional replacement. The sand layers are put in gradually according to their grain sizes: rather coarse grains at the bottom and fine grains at the top. The sand-bed is usually covered with one meter of supernatant water (LOGSDON 2003). As the process of biological filtration requires a fair amount of time in order to improve effectiveness of water treatment, SSFs usually operate at slow flow rates between 0.1 – 0.3 m3/h per square metre of surface (WHO n.y.). The water thus remains in the space above the medium for several hours and larger particles are allowed to separate and settle. It then passes through the sand-bed where it goes through a number of purification processes (HUISMAN 1974).

Due to the risk of inland flooding and (seawater) tidal surges from offshore storms, communities build earthen embankments around the ponds to prevent contamination. Local authorities and community members must be involved in the design height of the embankment—which should be equivalent to the highest pre-recorded flood level. In the geo-referenced area (Patharghata) this is equivalent to the tidal surge of Cyclone Sidr (2007). Constructed roadways are often a good reference point. In southern Bangladesh , rural roadways are built to at a ten-year flood return period, so exceeding this height according to the means of the community and/or project is recommended.
Pond embankments are best raised with soil preferably of a clayey nature. The final covering layer must be rich in clay. Embankments should be planted with native grasses and flora that have strong root systems to stabilize slopes and prevent erosion during the rainy season and in cases of tidal surge due to storms. In Bangladesh, the native kolmi (Ipomoea) has proven effective. Community members have also planted crops on the embankments, such as banana trees, medicinal plants and even small garden trenches in the middle of the slope. Beyond structural support, the horticulture helps diversify nutrition and can provide a source of income for maintaining the pond sand filter.
Fences should be installed to prevent animals from entering ponds reserved for drinking water. Community members must guarantee that the ponds selected for PSF construction shall not be used for purposes such as: washing, bathing, fish farming (natural fish however can be allowed), direct cattle access washing and watering. Furthermore:
•Fertilizers and other chemicals shall never be allowed to go into the pond.
•The flow of any polluting materials in the vicinity of the pond shall always be directed away from the pond.
•Latrines, cowsheds, garbage dumps, graveyards, fuel outlets and similar polluting structures shall not be constructed within a distance of 30 meters from the pond.
•Duck or poultry rearing hanging sheds shall never be constructed over the pond.

2.3 Photos de la Technologie

2.5 Pays/ région/ lieux où la Technologie a été appliquée et qui sont couverts par cette évaluation

2.6 Date de mise en œuvre de la Technologie

Si l'année précise est inconnue, indiquez la date approximative: :

• il y a moins de 10 ans (récemment)

2.7 Introduction de la Technologie

Spécifiez comment la Technologie a été introduite: :

• dans le cadre d'un système traditionnel (> 50 ans)
• par le biais de projets/ d'interventions extérieures

3.1 Principal(aux) objectif(s) de la Technologie

• réduire les risques de catastrophes
• s'adapter au changement et aux extrêmes climatiques et à leurs impacts

3.2 Type(s) actuel(s) d'utilisation des terres, là où la Technologie est appliquée

Les divers types d'utilisation des terres au sein du même unité de terrain: :

Oui

Précisez l'utilisation mixte des terres (cultures/ pâturages/ arbres):

• Agroforesterie

3.3 Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

• Non (Passez à la question 3.4)

3.4 Approvisionnement en eau

Approvisionnement en eau des terres sur lesquelles est appliquée la Technologie:

• pluvial

3.5 Groupe de GDT auquel appartient la Technologie

• gestion des eaux de surface (sources, rivières, lacs, mers)

3.6 Mesures de GDT constituant la Technologie

3.7 Principaux types de dégradation des terres traités par la Technologie

Commentaires:

Preventing salt water intrusion, the surface water quality and quantity is protected. Turfing and planting the embankment prevents erosion.

3.8 Prévention, réduction de la dégradation ou réhabilitation des terres dégradées

Spécifiez l'objectif de la Technologie au regard de la dégradation des terres:

• non applicable

4.1 Dessin technique de la Technologie

4.2 Informations générales sur le calcul des intrants et des coûts

Spécifiez la manière dont les coûts et les intrants ont été calculés:

• par entité de la Technologie

Indiquez la monnaie utilisée pour le calcul des coûts:

• dollars américains

4.3 Activités de mise en place/ d'établissement

	Activité	Calendrier des activités (saisonnier)
1.	Community consultation for Committee Formation	Before onset of rain
2.	Create PSF Users' Committee, agre on user contributions	Before onset of rain
3.	Committee / pond selection approved by local Government	Before onset of rain
4.	Technical orientation to PSF Committee, input on designs	Before onset of rain
5.	Excavation of Pond	Before onset of rain
6.	Embankment Construction	Before onset of rain
7.	PSF Construction
8.	Fencing
9.	Turfing and hortiuclutre on the embankment	Before onset of rain
10.	PSF Training on Media Selection and maintenance	Regular intervals throughout the year (every 1-2 months)
11.	Pond embankment maintenance	Before onset of rain

Commentaires:

In general, the community approach begins with several consultation meetings in the community (inclusive: gender balanced and representative of the diversity makeup of the community) and with municipal authorities. An Outcome Mapping process is initiated to observe signs that a village is prepared and mobilized to receive support for PSF and pond embankment construction. Families must be willing to participate and contribute in the construction and take complete responsibility for operation and routine maintenance.
During the initial phase, a PSF Users’ Committee is formed and approved by the municipal government. Its members make time to participate in trainings on the design, use, maintenance and community organization for managing a PSF. Importantly, the PSF User’s committee must seek public commitments toward the construction costs in cash and/or in kind (labor, construction materials, embankments plants, etc). In Bangladesh this was 10% and usually in kind. Roles and responsibilities of the PSF Users’ Committee:
1)Be responsible for regular operation, maintenance and cleanliness of the pond sand filter;
2)Ensure that the maintenance points for pond water quality is respected per the manual;
3)Advocate for local authorities to conduct regular water quality testing; and to promote household water treatment systems
4)Establish a system of collecting money from users for the regular maintenance;
5)Organize Committee meetings before the start of each season and whenever needed. Similarly if required organize a wider meeting with users in connection with resolving any O&M issues.
6)Care for the tools and other materials that may be purchased for the pond sand filter.
Selection of ponds for PSF construction should be participative with criteria agreed and communicated with the community members and local authorities. The following criteria are suggested based on Terre des hommes’ experience in Bangladesh:
•Ponds that are large enough to retain water throughout the dry season.
•The salinity of the pond water must not exceed 600 ppm at any time of the year.
•While the location of the PSF should be close to a family to ensure its security, it must be as centrally located as possible for ease of access
•Freely accessible to the public; ideally donated for public use.
•Ponds located on higher ground and thus more resistant to flooding / sea water intrusion.
•Space available for raising the embankments around the ponds
•Ponds most accessible to a largest segment of the population during disaster.
•Each PSF should have an effective drainage space and system.

4.4 Coûts et intrants nécessaires à la mise en place

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% des coût supporté par les exploitants des terres
Main d'œuvre	Pond Excavation and Embankment Raising	Person-days	180,0	5,0	900,0	10,0
Main d'œuvre	Pond Fencing Works	Person-days	20,0	5,0	100,0
Main d'œuvre	Masonry	Person-days	36,0	6,25	225,0
Equipements	Repairing tools	Set	1,0	15,0	15,0
Equipements	Tubewell/handpump	Pieces	1,0	35,0	35,0	10,0
Equipements	Sanitary Fittings	Set	1,0	100,0	100,0
Engrais et biocides	Bleaching powder for disinfection	kg	2,0	1,0	2,0	10,0
Engrais et biocides	Lime for cleaning	kg	50,0	0,5	25,0
Matériaux de construction	bricks	pieces	6000,0	0,075	450,0	10,0
Matériaux de construction	cement	50 Kilo Bags	50,0	5,75	287,5	10,0
Matériaux de construction	sand	cubic feet	52,0	0,375	19,5
Matériaux de construction	mild steel round bar	kg	210,0	0,75	157,5
Autre	Materials Transport Cost	Lump Sum	1,0	185,0	185,0	10,0
Coût total de mise en place de la Technologie					2501,5
Coût total de mise en place de la Technologie en dollars américains (USD)					2501,5

Si le coût n'est pas pris en charge à 100% par l'exploitant des terres, indiquez qui a financé le coût restant:

The project requested 10% contribution in kind (materials, transport, labor) from each community. The remaining costs were covered by the project.

Commentaires:

The budget is for raising a 100m perimeter length of embankment.

4.5 Activités d'entretien/ récurrentes

	Activité	Calendrier/ fréquence
1.	Repairing	Before onset of rains
2.	Cleaning	Before onset of rains

4.6 Coûts et intrants nécessaires aux activités d'entretien/ récurrentes (par an)

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% des coût supporté par les exploitants des terres
Main d'œuvre	two-monthly cleaning of filter materials	Person days	12,0	5,0	60,0	100,0
Main d'œuvre	Seasonal erosion control	Person days	12,0	5,0	60,0	100,0
Engrais et biocides	bleeching powder	bag	5,0	2,0	10,0	100,0
Coût total d'entretien de la Technologie					130,0
Coût total d'entretien de la Technologie en dollars américains (USD)					130,0

4.7 Facteurs les plus importants affectant les coûts

Décrivez les facteurs les plus importants affectant les coûts :

Comparatively, construction materials costs was reflected as the most expensive consideration.

5.1 Climat

5.2 Topographie

Indiquez si la Technologie est spécifiquement appliquée dans des:

• non pertinent

5.3 Sols

5.4 Disponibilité et qualité de l'eau

La salinité de l'eau est-elle un problème? :

Oui

Précisez:

groundwater table is salty along the Bay of Bengal, salt water intrusion. Tidal surge following cyclones also creates soil salinity.

La zone est-elle inondée?

Oui

Régularité:

fréquemment

5.5 Biodiversité

5.6 Caractéristiques des exploitants des terres appliquant la Technologie

5.7 Superficie moyenne des terres utilisées par les exploitants des terres appliquant la Technologie

5.8 Propriété foncière, droits d’utilisation des terres et de l'eau

Propriété foncière:

• individu, sans titre de propriété
• individu, avec titre de propriété

Droits d’utilisation des terres:

• individuel

Droits d’utilisation de l’eau:

• accès libre (non organisé)

5.9 Accès aux services et aux infrastructures

6.1 Impacts sur site que la Technologie a montrés

Impacts socio-économiques

Production

Disponibilité et qualité de l'eau

Revenus et coûts

Impacts socioculturels

6.2 Impacts hors site que la Technologie a montrés

6.3 Exposition et sensibilité de la Technologie aux changements progressifs et aux évènements extrêmes/catastrophes liés au climat (telles que perçues par les exploitants des terres)

Extrêmes climatiques (catastrophes)

Catastrophes climatiques

	Comment la Technologie fait-elle face à cela?
sécheresse	bien

Catastrophes hydrologiques

	Comment la Technologie fait-elle face à cela?
onde de tempête/ inondation côtière	très bien

Commentaires:

PSF serves as disaster resilient Technology that helps residents in coastal villages along the Bay of Bengal to cope with the effects of climate change; such as increased incidence and intensity of storms and salt water intrusion.

6.4 Analyse coûts-bénéfices

Quels sont les bénéfices comparativement aux coûts de mise en place (du point de vue des exploitants des terres)?

Quels sont les bénéfices comparativement aux coûts d'entretien récurrents (du point de vue des exploitants des terres)?

6.5 Adoption de la Technologie

• > 50%

De tous ceux qui ont adopté la Technologie, combien d'entre eux l'ont fait spontanément, à savoir sans recevoir aucune incitation matérielle, ou aucune rémunération? :

• 0-10%

6.6 Adaptation

La Technologie a-t-elle été récemment modifiée pour s'adapter à l'évolution des conditions?

Non

6.7 Points forts/ avantages/ possibilités de la Technologie

Points forts/ avantages/ possibilités du point de vue de l'exploitant des terres
The Technology is useful for supplying drinking water at household level and supports cultivation of fruit trees, medicinal plants and vegetables at the pond embankment, above the flood line.

Points forts/ avantages/ possibilités du point de vue du compilateur ou d'une autre personne ressource clé
The Technology is conducive for ensuring supply of water for drinking, cooking and irrigation purposes if the community is motivated and understands the impact of PSF when faced with water shortage during dry season and other disaster events.

6.8 Faiblesses/ inconvénients/ risques de la Technologie et moyens de les surmonter

Faiblesses/ inconvénients/ risques du point de vue du compilateur ou d'une autre personne ressource clé	Comment peuvent-ils être surmontés?
Every five to six weaks, the PSF filter media needs to be maintained, requiring some training, as well organising labor and collecting petty funds for bleaching powder.	The PSF User's Manual has been translated into local language with images and tips for maintenance. This is distributed following the training. The PSF User's Committee must regularly collect user fees for smooth operations. A bank account promotes transparency. Sale of crops harvested on the embankments can help defray costs of maintenance.
Although not laborious, the hand pump requires some degree of force, and the taps are often a target of children's play.	Children should be supervised and small children must not be allowed to operate or play near the pump. Investing in sturdy tap systems is essential.
The bio-film will form after seven days of operating the pump.	Users must boil or treat water very carefully in this period.
Private owners could lose interest availing their asset for the communty. For example, they may start using the pond for fish farming in order to sustain their livelihoods.	Formal agreements with the municipality about the usage rules for the pond, and public commitments taken by the pond owners are important. Posting signboards that identify the pond as "Drinking Water Only" and specify forbidden activities is also helpful. Owners can take a higher share of crops cultivated on the embankment.

7.1 Méthodes/ sources d'information

7.2 Références des publications disponibles

Titre, auteur, année, ISBN:

SSWM University Course Module 6: Disaster Situations: Planning and Preparedness Further Resources: Water Purification Slow Sand Filtration, Marco A. Bruni, Dorothee Spuhler (seecon international gmbh), 2012.

Disponible à partir d'où? Coût?

https://www.sswm.info/sswm-university-course/module-6-disaster-situations-planning-and-preparedness/further-resources-0/slow-sand-filtration

Titre, auteur, année, ISBN:

Pond Sand Filter (PSF) Manual – community operation and maintenance, Laxman Kharal (Terre des hommes), 2012

Disponible à partir d'où? Coût?

Contact: info@tdh.ch

Titre, auteur, année, ISBN:

Guidelines for Drinking Water Quality, 4th Edition, WHO, 2011

Disponible à partir d'où? Coût?

http://www.who.int/water_sanitation_health/publications/2011/dwq_guidelines/en/