Easy method to get safe drinking water

Here is some good news for the flood-affected people suffering from an acute crisis of pure drinking water.

Professor K Siddique-e-Rabbani, chairman of Department of Biomedical Physics and Technology of Dhaka University, along with a group of his students, yesterday claimed to have invented a method of killing harmful bacteria in floodwater using nothing but sunlight.

“Now, people can drink floodwater even if the disaster washes away their earthen stoves,” said a smiling Rabbani, while demonstrating the method at a press conference at Dhaka Reporters Unity.

The professor claimed he had been working on the method since the late 80s to remove bacteria from floodwater that are responsible for common diseases like Diarrhoea and Cholera in the country.

Flood-hit people can use the method to purify water on the rafts and boats, he said.

In the process, the DU team used ordinary materials like dry straw, bamboo tray, black paint and transparent polypropylene (PP) bags.

At first, they painted the inner side of a bamboo basket black and then kept three tightly-knotted PP bags of floodwater inside it.

After that, they wrapped the upper side of the basket with two transparent plastic sheets with a clearance of two-cm in between and kept it under sunlight.

Most of the heat entering the basket through the plastic sheets are absorbed inside the basket and creates the greenhouse effect, claimed Rabbani.

Thus heat is produced and temperature inside the basket can be up to 70 degrees Celsius in less than two hours, killing the germs and the water can be drunk then, he said.

The professor yesterday also showed a steel-device that is made using the method named “Solar water Pasteuriser”.

Temperature above 60 degrees Celsius is enough to kill the germs that cause diseases like bacteria-related Diarrhoea and Cholera in 30 minutes, said the DU professor.

“On the other hand, the Sun's UV rays destroy the bacteria too and thus makes the method more efficient,” he added.

However, water kept in the PP bags need to be filtered using several layers of clothes to get rid of the dirt first.

The professor claimed that the team had carried out the test at DU's Centre for Advanced Research in Sciences (CARS) several times before and it showed “positive results every time”, but said the method is unable to kill virus-related germs.

Contacted, Latiful Bari, principal scientist at CARS, said the temperature produced in the method can kill the bacteria that are harmful to humans.

“Since the method is used on the surface water during monsoon, it is free of toxic metals like arsenic present in the groundwater in many districts,” opined the scientist.

However, heavily polluted water sources like the Buriganga river or water contaminated with insecticides cannot be purified using such a simple method, he cautioned.

Unlike other plastic materials, PP bags are non-carcinogenic. As a result the water heated in these bags remains harmless, he assured.

If any object is carcinogenic, it means it contributes to causing cancer in human bodies.