Sustainable technologies

We always use technologies that are low cost, appropriate to the local financial and geographical conditions and within the technical capacity of the benefiting community to operate and maintain.

So that communities are responsible and feel a sense of ownership for their projects they must be involved in all stages of the work.

We aim to use technologies which include locally sourced materials and spare parts which can be easily purchased and transported.

In addition to this, our partners provide training to local communities so that they can carry out operation and maintenance work themselves.

This ensures that communities can sustain their projects after WaterAid ends its support, with possibilities to extend or replicate their projects in the future.

Points to consider before designing a solution

Water supply

Deciding which type of water supply technology will suit a community depends on their needs and the water sources available in the area.

Drinking water supplies must use uncontaminated sources, as treatment chemicals and equipment are too expensive for benefiting communities.

Rainwater harvesting

A large-scale rainwater harvesting scheme at Tefo Primary school in Ethiopia.

Credit: WaterAid / Caroline Irby

Falling rainwater is some of the cleanest naturally occurring water available and where it falls regularly there is scope to collect it, before evaporation takes place and before it becomes contaminated.

This is called rainwater harvesting. Water is generally collected from pre-cleaned roofs, where it runs via guttering into a storage tank.

However, using a clean surface water or groundwater source is often preferable as the quantity and quality are generally more reliable.

Uncontaminated surface water supplies include small upland rivers, streams or springs.

Technical information on rainwater harvesting 

Spring protection

In some areas springs can be tapped, protected and used directly at their source.

Spring protection to prevent contamination includes fencing the surrounding area to prevent animals entering, a concrete retaining wall and outlet pipe to keep the area clean while buckets are filled, and a drainage area below to prevent pools of stagnant water collecting.

Technical information on spring protection 

Subsurface dams

Where there is seasonal underground movement of water, such as below dried river beds, it may be useful to construct subsurface dams to retain a usable supply.

Technical information on subsurface dams 

Gravity-fed schemes

Men working on a gravity flow scheme in Ethiopia.

Credit: WaterAid / Caroline Penn

In hilly areas, water can be piped down to communities from higher water sources through gravity-fed schemes.

The spring or small unpolluted stream is tapped, dammed and protected at its source before being piped down to storage tanks in villages.

Distribution pipes then feed protected tapstands allowing people to draw water close to their homes.

This method avoids the potential mechanical problems of pumps, but still needs careful maintenance to keep the water clean.

The initial costs for these schemes are high due to long pipelines and storage tanks, but the running costs are very low. Conversely, the level of service is high.

Technical information on gravity-fed schemes 

Hand-dug wells

A concrete ring is lowered into a hand-dug well in Nepal.

Credit: WaterAid / Caroline Penn

Far more people worldwide rely on groundwater for their drinking water. Groundwater is usually safe to drink because permeable layers of earth act as fine filters removing bacteria and other impurities as water seeps through.

Hand-dug wells are the most common method of abstracting groundwater in the developing world.

However traditional hand-dug wells often dry out as they are too shallow and also become polluted as the sides are not lined and the top is uncovered.

Without proper drainage, pools of water can form around the wells and these can act as breeding grounds for disease-carrying insects like mosquitoes.

Our technology uses the traditional hand-dug methods, with additional features to prevent these problems. Hand-dug wells are usually 1.2m in diameter to allow sufficient digging space. Depths vary, from shallow wells at 5m to deep wells over 20m, but all are deep enough to ensure the water table can still be reached during the dry season.

Hand-dug wells are also lined to prevent pollution and make them more stable - particularly those built in the dry season which are liable to collapse in the wet season.

Linings are usually made by either pouring concrete into steel moulds or using pre-cast concrete rings. At the level of the water table, linings have porous walls and pre-cast rings are left unjointed to allow water to ingress into the well.

Once dug, the wall of the well is raised with a concrete upstand and cover slab to prevent polluted surface water seeping back in. Drainage channels are also formed to stop the build up of wastewater.

Rather than digging new wells, some programmes rehabilitate traditional hand-dug wells.

Traditional wells are dug deeper and wider, lined, then sealed and protected to prevent contamination.

Technical information on hand-dug wells 

Tubewells and boreholes

Abdul and his wife use the sludging method to install a tubewell in Bangladesh.

Credit: WaterAid / Abir Abdullah

In areas with lower water tables, where water needs to be collected from a greater depth or where ground conditions permit hand drilling or auguring to be carried out, WaterAid uses other technologies including tubewells or boreholes.

Tubewells are small diameter holes drilled by hand-powered methods of auguring and sludging.

Although hand-dug wells can retain more water, tubewells can be built quickly and cheaply, require less maintenance, can reach greater depths and are safer to construct. However, they are reliant on drilling tools which may not be readily available.

Where there are harder rocks and the water table is very low, engine-driven augers and rock drills are necessary to cut through the earth to depths of 100m or more.

These are called boreholes and are only used when absolutely necessary as finding water takes time, money and effort through hydrological surveys and they are also expensive to construct and run.

Even at great depths, handpumps can be used to draw water from tubewells or boreholes with narrow diameters.

However, where there is a higher demand for water and only deeper sources are available, wide tubewells or boreholes are used and the water then has to be pumped to the surface using diesel or electric engines.

The water is then usually stored in large tanks before being piped to tapstands in surrounding villages. The diesel or electric pumps needed are expensive to maintain.

Technical information on tubewells and boreholes

Handpumps or buckets?

Christin Pede at a handpump in Zambia.

Credit: WaterAid / Jon Spaull

Where hand-dug wells are built communities have to choose whether to use a handpump or a dedicated bucket and windlass.

Deciding between them depends on the well's yield, the ability of the community to pay for maintenance and the type of tools and spare parts available at an affordable cost.

Where they are appropriate and affordable handpumps are preferable as they are sealed around the well and so prevent contamination.

However, where handpump spares are very hard to come by or are too expensive communities can choose a bucket and windlass instead.

Although easy to operate and repair, using a bucket and windlass does not allow the well to be sealed as it must be opened to collect water, which can allow pollution.

However providing the well is covered when it isn't in use, and there is a dedicated bucket and windlass to ensure minimum human contact, then contamination is minimised. In newer, improved designs, the rope is totally covered to reduce the possibility of contamination.

Technical information on handpumps 

Water treatment

It may not be possible to locate an unpolluted water source for domestic supply. If this is the case it will be necessary to introduce water treatment techniques in order to ensure that contaminated water is not distributed.

Technical information on water treatment
Technical information on disinfection 

Sanitation

Credit: WaterAid / Jon Spaull

Hygienic lavatories are just as important as clean water to improve health and WaterAid uses various technologies to ensure communities gain access to safe sanitation.

Given sensitive guidelines and a little technical help, families can build latrines for themselves at very low cost.

Dry pit latrines

The most common type of latrine is the dry pit latrine. The main criteria are that the pit should be at least three metres deep and completely above the water table.

The squat slab covering the pit should be strong and easy to clean, with a keyhole shaped drop hole and foot pads.

It should be pre-cast away from the pit and then placed over it. A shelter built of local materials can then provide privacy.

Ventilated improved pit (VIP) latrines

VIP latrines also have vent pipes to take smells and insects away. Insects, attracted to the source of light in the vent pipe, are trapped at the top by a fly screen.

Pour flush latrines

Where people use water to clean themselves after they have visited the latrine, pour-flush latrines are favoured instead.

In these the latrine pan is placed a few metres away from the pit and a pipe with a u-bend connects the two. The u-bend stops flies and smells escaping from the pit.

Composting latrines

Composting latrines benefit local agriculture by creating a safe, renewable source of fertile compost from human waste.

In their simplest form a tree is planted on a filled latrine pit - however a twin pit latrine offers a more permanent solution. One pit is used at a time, and after each use soil and ash is added to dry the contents out. Once it is full a further layer of soil and ash is placed on top and the pit is covered. The second pit is then used until it too is full. At this time the first pit is dug out and its contents used for compost or, if not enough time has passed, it is moved to a secondary compost point.

Technical information on sanitation and latrines
Information on hygiene education  

Urban solutions

Because of the higher population densities in urban areas different technologies are often needed.

Piped supply

While tubewells can be used to provide water, where possible a preferable solution is to negotiate with the local government or water suppliers to connect slum communities to the city's piped supplies and then provide communal tapstands managed by the beneficiaries.

WaterAid and its partners also help communities arrive at agreements with municipal suppliers.

Sewerage systems

Pit latrines can fill too quickly and the large numbers needed can eventually pollute underground water supplies.

In some cases septic tanks are used but where possible, we are helping community groups build sewerage systems that can be linked to the city's systems and treatment works.

WaterAid also helps these groups to build and manage communal toilet and washing facilities.

Water resource management

Water tables are falling dramatically in many parts of the world due to over-abstraction of water by agriculture and industry, a problem that will be exacerbated by climate change.

In recognition of this, WaterAid is committed to a policy of ensuring that all its future water supply and sanitation projects address the issues of water depletion and contamination through appropriate water resource management.

See examples of sustainable technology in action

Download the new technology issue sheet
( PDF 787KB)