Water Pumps: the Ram Pump

Ram pumps were first developed over 200 years ago by Joseph Montgolfier, who is most famous for his invention of the hot-air balloon.  These pumps do not need electricity or gasoline to operate; they work solely with the kinetic energy that is inherent in falling water.

A ram pump installation consists of four typical components:

1. A water source uphill of the ram pump,
2. A pipe, which carries the water from this source to the pump
3. The ram pump itself, and
4. Another pipe which carries the water to its point of use.

 As the water runs downhill from the source to the ram pump, it gains force and velocity.  When this velocity reaches a determined point, the water closes a valve in the ram pump known as the "impulse" or "waste" valve.  The force of the water against the now closed impulse valve causes pressure to build inside the pump.  The water sends high-pressure shock waves in all directions (the "water hammer," or "ariete" in Spanish, from which the pump gets its Spanish name, "Bomba de Ariete").  These shock waves open another valve, the delivery check valve, and water squirts through reaching altitudes of up to ten times greater than the vertical distance from the water's source to the pump. An air vessel installed in the pump acts as a kind of regulator which keeps the flow at the top steady, instead of delivered in bursts, as the pump internally functions.

Ramp pumps are affordable, durable and reliable 

The ram pumps used by the AIDG are manufactured using supplies available at any plumbing store, which makes them far more economical for rural families and also ensures ease of replication wherever the pumps are needed. Because ramp pumps have few moving parts, they are easy to maintain, very reliable and have a long operation life. The capacity exists to manufacture large custom pumps for installations with big flows or big elevation changes in which the standard pumps can't do the job.

Solar Water Heating

Solar heating is one of the oldest uses of solar energy, a low cost collector in tropical climates can easily meet the hot water needs of a small family.

Solar Water Purification

 Solar water purification has long been the ugly duckling of the development community. Dismissed often as too slow, too expensive, too energy inefficient. While these problems are true of most solar purification designs these designs are not without their merits. For areas where long term maintenance of a filtration system proves difficult a solar purification system can be an appropriate solution. And it is ideal for situations where membrane filtration or chemical treatment is too expensive and space concerns make slow sand filtration impractical.

Slow Sand Filtration

Also known as biosand filters, slow sand filters do not require any special type of sand, but rather can make use of any fine-grained sand. Typically, river sand is used, as it is the most freely available in the majority of areas. Slow sand filters have been and are used in many municipal water treatment stations around the world. Municipal filters are usually large circular boxes of up to ten meters in diameter, with a filter depth of one to two meters. The family-sized filters may be as little as 30 cm in diameter. They do, however, still maintain a filter depth of around one meter. This depth is essential for the effectiveness of the filter.

Sand Sand and More Sand 

The filter material consists of several layers of different sized sand and gravel.At the bottom, where the water exits the filter, is a layer of normal gravel.  Moving from the bottom to the top, one finds several levels of progressively finer sand. The top layer is fine sand with a depth of around 50cm. A coating of microorganisms (bacteria, fungi, protozoa, rotifera) grows on this final layer, giving the filter its other common name - "biosand" filter. These microbes filter or metabolize any bacteria in the water; the sand and gravel filter out the particulate and organic matter that may slip by. This process is essentially the same as the filtration that is carried out as rain and ground water flows through the soil and reaches underground reservoirs.

Many different types of storage containers have been used to hold the sand: oil drums, concrete tubes, and plastic barrels. AIDG uses plastic barrels, avoiding the oxidation and bad taste that sometimes is associated with metal drums while providing easier transportability and assembly than concrete tubes.

Properly managed sand filters remove 96%-98% of water borne pathogens such as E. Coli and Giardia, producing a positive significant impact on the health of target users. The greatest effect is expected for young children, who are extremely susceptible to diarrheal diseases caused by exposure to contaminated water. Diarrheal disease causes approximately 2 million deaths per year among children in developing countries.

The implementation of sand filters, particularly when combined with other sanitation and hygiene practices is an effective and economical way of dealing with this major problem. The primary drawbacks of slow sand filtration include the need for diligence in the maintenance of the filter and the speed of filtration (slow).

For further information, book is a good resource. It is available in Electronic form on the World Health Organization website