water purification

Water treatment plant

In many places around the world, purified water is not always readily available. But sunshine is. For example, purified water is a big problem, as two thirds of Kenya lies in an arid or semi-arid area.

Scientists around the world are looking to bring clean water to those in need by coming up with innovative ways to purify water

  • direct-contact membrane distillation (DCMD) system – removes the salt out of otherwise undrinkable ocean water
  • Midomo machine, which holds and filters water while the machine is rolled. The machine’s innovation is based on the fact that the daily average distance a person in Africa travels for water is 3.7 miles.
  • sun powered water purification device – Rose-Hulman Institute of Technology students created a device that harvests solar energy to pasteurize and filter drinking water. Designed for a family of five, from materials easily obtained in Kenya, the device can purify 15 liters of water per day.
  • UV water disinfection system is manufactured by Water Health International. The simple machine can clean enough water every day for 1,000 people. Using science no more complex than the ultraviolet light emitted by an unshielded fluorescent lamp, Ashok Gadgil built a simple, effective, and inexpensive water disinfection system.
  • Clay Water Filters for Ghana – Pure Home Water, Ghana manufactures and distributes AfriClay Filters in an effort to bring clean water to 1 million people. Sediment and bacteria are filtered out in several ways: * Physical straining: the particles are too large to fit through the pores in the clay * Sedimentation or adsorption: particles come to rest on or stick to the clay * Inertia: friction in the pores keeps the particles from passing through Bacteria are also killed by a coating of colloidal silver (a disinfectant), which we apply to all filters that pass our quality control tests. While sediment and bacteria are filtered out, the molecules of water are small enough to pass through the pores in the clay. more…
  • Nazava Water Filters – Indonesia – In Indonesia, 150 million people cannot afford safe drinking water. Easy-to-use household water filters that provide a continued flow of safe drinking water, without wood, propane, or electricity. 1 million people with improved health and an average annual savings of $70/household. As one of the The Tech Awards 2013 Laureates this project has been recognized as providing an innovative solution to a problem with significant social impact.

What’s the problem?

  • Ask – Millions of people all around the world do not have access to clean water. What are some of the challenges facing the designers of water purification systems for use in poor countries?
  • Imagine – While there are many different water purification systems in use today, many are expensive, require electricity to run or are difficult to repair. What kinds of water purification systems are currently available? Will there be electricity to run the equipment at the location where it is used? How can the selective transport of molecules be used for water purification?
  • Design, Build – Simple reliable systems are most needed. How will the equipment be fixed if it breaks where it is used hundreds of miles from a technician?
  • Improve – Finding alternate sources of power extends the usefulness of a water purification system. Can the system work with solar or wind power?

That’s engineering

  • Polar molecules have a slight positive charge at one end of the molecule and a slight negative charge at the other end of the molecule because of how the atoms and electrons are arranged. Alcohol is polar.
  • The electrons in a nonpolar molecule are distributed evenly so there is no difference in charge throughout the molecule. Oil is nonpolar.
  • Polar molecules are attracted to other polar molecules while nonpolar molecules are attracted to other nonpolar molecules. However, polar and nonpolar molecules repel each other, which is why the vegetable oil and rubbing alcohol do not mix.
  • Cell membranes are composed of a phospholipid bilayer. Phospholipids have a polar “head” and a nonpolar “tail.”

Engineering ideas

  • membrane, polar, nonpolar, electron, positive, negative, charge, molecule, biochemistry,

Do it
Here are some challenges for you to work on…

  • Glitter globe – create a toy to demonstrate different chemical properties. Polar and nonpolar molecules repel each other, which is why the vegetable oil and rubbing alcohol do not mix.
  • World saving water filter – engineers use science to turn water from dirty to drinkable.

Learn more…

  • Water and Engineering
  • National Academy of Engineering’s Grand Challenges
  • WaterAid, an international nonprofit organization that seeks to provide safe domestic water in Africa, Asia and Central America.
  • Ashok Gadgil – biography