After a dull public response put the board's plan of turning sewage into drinking water on the backburner, BWSSB is now setting its eyes on generation of biogas with the treatment of sewage.

“We are planning to use the biogas that would be produced from sewage for generating electricity. If all the sewage discharged in the city is used for this purpose, the current power crisis can be solved to some extent,” said a BWSSB official.

The BWSSB will construct 13 plants around the city to generate biogas from sewage.

Three of the plants will be constructed near the old sewage treatment plants.

The sewage will be directed into a specially designed bio-digester, which will facilitate the generation of biogas (mostly methane) from it. The biogas thus generated will be used as fuel for the generation of electricity, sources said.

Sewage becomes less toxic after biogas is generated as some of the poisonous gases are released in the process.

Thus, the residue can be used as manure.

After the process, the sewage water can be treated and used for non-potable purposes such as watering plants and washing clothes.

Tertiary-treated sewage is also considered safe for drinking after ultra-filtration, sources added.

The BWSSB had organised a seminar in June 2009 to create awareness about the generation of biogas from sewage, in which a delegation from the Swedish Energy Agency had also participated.

The idea of generating biogas from sewage had been discussed in the seminar.