Use of Solar Heat for Safe Drinking Water

Use of Solar Heat for Safe Drinking Water


The idea behind this project is to use solar heat for destroying the disease causing organisms often present in our drinking water. Most of the intestinal pathogens in vegetative form gets killed at a water temperature of 60’C in about ten minutes. This principle is being used here to make water suitable for our daily consumption needs at no cost at all, taking the aid of abundant sunlight during the day hours.


To employ sunlight, in order to kill disease-causing bacteria in our drinking water and make it safe to be consumed.

Materials Required

  • Transparent plastic (food-grade) water bottle of 1 litre capacity. PET bottle 1 litre.
  • Glass bottle of 1 litre capacity.
  • Sterilized or boiled or bottled water
  • H2S test bottle
  • Known culture of bacteria present in contaminatedwater, which turns black in H2S medium.
  • Black paint / black paper / white paint
  • A pair of plastic gloves


PET, glass bottle and plastic bottles are half painted black and another bottle painted half white, all on the outside. Two more bottles are painted black and
white completely. Fill each of the sets with sterile or bottled water. Add one drop (0.1 – 0.5 ml) of culture containing H2S bacteria. Now keep the bottles exposed to sunlight. Every 2-8 hrs, water in the bottles are tested to detect the presence of H2S bacteria. This amount of time is required to kill the bacteria. Record the temperature of the water in the bottles at every bacterial check. Observe and find out in which of the bottles most of the bacteria gets killed, after how much time and why?

Data Interpretation

Determine the time required by solar heat (uninterrupted sunlight is essential) to kill bacteria in drinking water, along with what temperature is requires. Prepare graphical presentations.


  1. Development of low cost technology for safe drinking water.
  2. Utilization of solar heat.
  3. Other innovative methods of killing bacteria in water could be tested including the bioassay test.
  4. Can you try to design a continuous flow water purification system using this principle?


Source: Harness water resources for a better future - Activity Guide for the 13th National Children's Science Congress