Water Purification Powered by Microorganisms Living in the Soil

"Don't pick that up from the ground; it's got germs in it!" is a phrase that has come out of the mouths of countless mothers and fathers. However, the microbial activity could start to be used for quite the opposite—purifying water. Researchers at the University of Bath in the UK have been studying the possibility of harnessing microbial activity in a field to generate electricity to power water purification systems. Called soil microbial fuel cells (SMFCs), these easily manufactured devices produce renewable energy in a very unconventional way.

The starting point is electricity generated by microorganisms in the soil. The organisms that produce this electric current are known as electrogenic since they emit electrons through their cell membranes as they carry out metabolic processes. The British scientific team has developed a system based on two carbon electrodes separated by four centimeters. One of them, which acts as an anode, is buried, while the cathode is exposed to the atmosphere. In this way, electrons move from the anode to the cathode, connected to an electric circuit, generating electricity. It may be a weak electric current of only 0.4 mW. Still, if several rows of electrodes are installed, the energy can be multiplied to provide a usable output for various purposes. Finally, the electrode array is connected to a battery to store this clean, renewable energy. The electrodes cost no more than €4 per unit, although they could be made even cheaper with large-scale production. 

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Pure water in cut-off areas

Northeast Brazil is a semi-arid and underdeveloped area. In many of the villages, access to drinking water and electricity is difficult, if not impossible. That is why, in conjunction with geographers from the Federal University of Coerá and a group of chemists from the Federal University of Rio Grande do Norte, the researchers realized that the inhabitants of Icapuí, a fishing village in the area, could benefit from the breakthrough. Until now, its inhabitants depended on rainwater, which underwent a chlorination process. Fortunately, this innovative technology project could improve their situation by using an electrochemical reactor to carry out the operation.

In tests undertaken in the locality with elementary school students' help, it has been possible to produce up to three liters of drinking water per day. The goal is to cover an entire family's daily needs with the use of a single, easily installed device. Electrochemical reactors have proven their efficiency in laboratory conditions, but this project has shown that they can be an effective technology in everyday life. In fact, the first prototypes have operated uninterruptedly for 140 days. 

Besides producing drinking water, one of the initiative's priorities has been to educate the Icapuí school students on the values of sustainability and respect for the environment. Thanks to this work, the students have learned about the device's scientific principles, installation, and maintenance.

Source:  Science Daily