By: Sanjiv Sambandan Flexible Electronics Lab, Department of Instrumentation and Applied Physics, IISc, Bangalore The research: Developing a technology to filter extremely dirty water, that can be encased in a small, portable device and runs on very little power. There are plenty of technologies available in the market to treat water. But most of them are capable of treating only tap water and are either membrane-based or use chemicals. In remote villages or areas hit by natural disasters, ponds and wells still remain the primary source of water, but this is not fit for drinking. Traditional water-treatment technologies are not designed to treat very dirty or waste water. Membranes need to be changed and chemicals must be disposed of in a safe manner. At the Flexible Electronics Lab at the IISc, we have been working on the idea of developing a more efficient water treatment technology since 2010; a small, portable, maybe even a hand-held device that could convert very dirty water into drinkable water. It was only a year later that we seriously started working on the project. We used electric fields to achieve the objective. When an electric field is established in a container with water, the impurities and small particles get polarised and are then attracted to each other. Smaller particles coalesce into larger granules while remaining suspended in water. These granules can then be filtered easily, using a normal tea filter or a clean cloth. For our tests, we used water from Mavalipura, near Bangalore, where the water quality is really bad, and the results we achieved were satisfactory. There was no new physics to the experiment that we performed, as the problem was essentially an engineering issue. The key was to understand how electric fields permeate ion rich fluids and how they interact with neutral impurities. This understanding helped us identify the field strengths needed to maximise this interaction and then use this concept to improve the filtration process. We have managed to develop a technology that can convert very dirty water — from ponds, lakes, wells and even waste water — into drinkable quality. Unlike in the traditional filtration technologies, there is zero wastage of water. In fact, even the waste water can be reused.The entire instrument can be encased in a one-litre bottle and needs very little power to run, either a battery or hand-held dynamo will serve the purpose. The instrument can filter one litre of water in a maximum time of about 10 minutes, though there have been occasions where one litre of water has been treated within three minutes. So far, we have tested the newly developed water purifying system in laboratories and now we are trying to take the technology to the field. We estimate that a bottle filter could cost about Rs 1,000, but the prices will come down substantially as we increase the capacity of the instrument. The new filter and our ideas on how to introduce the technology to society was recently awarded the first place at a competition organised by Google in Zurich, Switzerland. For your research to be considered for this column, please write to Senior Editor Amitabh Sinha at amitabh.sinha@expressindia.com
