Well

A well is a structure created in the ground by digging or drilling to access groundwater in underground aquifers.

The well water is drawn by a mechanical or electrical pump. Generally, the water is pumped out to a faucet where the community can immediately fill up their water containers or it is pumped into a water storage tank.

When working in rural communities, it is important to choose the right technology to pump the water out of the well. This can depend on many factors, including:

• Depth of the well
• Size of the well
• Amount of available water
• Availability of electricity
• Initial investment cost
• Annual maintenance cost

A hand pump in Cameroon.

The following are three types of technologies Aguayuda is implementing to pump water out of a well.

Hand Pump

A hand pump uses manual power supplied by the user to pump water and therefore does not require electricity. It also has the advantage that the water can be pumped directly into the individual water containers by the people and therefore does not require water storage tanks. Hand pumps also require minimal maintenance and are a proven technology in many rural communities all over the world.

Windmill

A windmill in Colombia.

A windmill is a device that consists of blades, a pump rod and a piston. When wind rotates the blades, the movement causes the pump rod to rise and fall. The pump rod then enables the piston to rise as it draws water from the aquifer. During this movement, a special valve in the piston closes to ensure no water escapes as the piston then pumps water into a storage tank. This process continues as long as there is sufficient wind to rotate the blades.

Windmills do not require electricity and can work at greater depths than hand pumps. However, the initial cost is higher and maintenance is required every 6-12 months.

Solar Pumps

Solar panels in Colombia.

A solar pump is similar to an electric pump, except it obtains its electricity from the sun through the solar panels. The major advantages of a solar pump are:

• Uses clean, renewable solar energy and does not produce greenhouse gases.
• Does not require diesel or gasoline supply.
• Operates quietly and maintenance-free.
• Life expectancy is over 20 years.

Rain Harvesting

Rain harvesting is the process of capturing rainwater from roofs or other surfaces through gutters and storing it in a water storage tank.

A rain harvesting system will provide a household with an independent clean water supply. However, to assure that the captured rainwater remains potable the system needs to be built with the following quality components:

Rain Gutters: Collect the rainwater from the roofs.

Rain Heads: Separate leaves and debris from the rainwater and to assure that animals, snakes and insects such as mosquitoes cannot enter the captured rainwater.

This rain harvesting system was installed by Aguayuda in 2011.

First Flush Diverters: Prevent the first downpour of water from entering the water storage tank. This is important because this water could be contaminated by pollutants from the roof such as bird droppings.

Black Closed Water Storage Tanks: Prevent animals and mosquitoes from entering the water. Closed water storage tank prevent bacteria and viruses from spreading due to insufficient lighting and organic matter (food).

A rain harvesting system requires minimal maintenance and is affordable. Additionally, they can be sustained by each family individually, which therefore allows the families to become directly involved with improving their quality of life.

Windmill

A windmill is a device that consists of blades, a pump rod and a piston. When wind rotates the blades, the movement causes the pump rod to rise and fall. The pump rod then enables the piston to rise as it draws water from the aquifer. During this movement, a special valve in the piston closes to ensure no water escapes as the piston then pumps water into a storage tank. This process continues as long as there is sufficient wind to rotate the blades.

Windmills do not require electricity and can work at greater depths than hand pumps. However, the initial cost is higher and maintenance is required every 6-12 months.

This windmill was installed by Aguayuda in 2009.

Pipeline

The water distribution system consists of PVC piping connected to unions and elbows with a faucet at the end.

The advantage of using PVC piping include the following:

• Low cost
• Availability of parts
• Low maintenance
• Easy installation

Building a water distribution system is an excellent project that can be done with the community. Generally the men of the community dig the trenches for the pipe, while other members of the community connect the pipe and glue them together.

This pipeline was installed in 2011.

Filtration

Membrane filtration is widely used for water purification. All modern membrane filters are of the crossflow design, typically using spiral-wound or hollow-fiber membrane configurations. The pore sizes of these membranes cover a very wide range that reaches from less than 0.001 micrometers to more than 2.0 micrometers.

This range has been subdivided into four filter categories that with their decreasing pore sizes will retain ever smaller particles or molecules while always letting the water pass. Decreasing pore sizes require higher operating pressure (i.e. higher energy consumption) and a corresponding higher capital cost and higher operating cost. For a certain filtration task therefore, the category chosen is always the one that permits the largest pore size without letting any of the undesired components pass through the membrane.

The four categories, their retention capabilities, their pore size ranges and their operating pressure ranges are shown on the graph below.

 

For most water purification applications spiral-wound R.O. or hollow-fiber UF/MF membrane systems are being chosen, for two fundamentally different purposes.

The inside of a membrane.

R.O. is always required when salt has to be retained. For a typical sea water desalination application working with 35,000 ppm of TDS (salt) the pore size is 0.0008ηm and the operating pressure is ±850 psig. Due to the higher osmotic pressure higher salt concentrations will require even higher operating pressure, while for brackish water or only slightly saline water the operating pressure can be as low as 200 psig.

UF or MF systems are widely used to filter sweet (non-saline) water where particles in the macromolecular and microparticulate ranges have to be removed. These ranges include all bacteria and most viruses.

NF systems are only used in rare cases where specific components in the molecular size retention range of these filters need to be removed.

Often however, MF and UF are used for prefiltration upstream of R.O. systems. For very large desalination systems NF can be found to prefilter the feed to R.O. systems.