A lack of sewage means a shortage of water and infection - a giant sewer tunnel is part of the solution

- When we clean, all the water is poured directly into the river.

All the water from toilets and bathrooms is also flushed into the river, says Samrin Khan, a housewife living in Bombay.

In India, nine out of ten cities lack functioning sewage networks.

And where there is - like in Bombay - a third of the 20 million inhabitants are still not connected and the dirty water causes a lot of diseases.

To deal with those emissions, a huge tunnel is being dug through Bombay.

And the Swedish Environmental Institute is on site and participating in the construction.

See more in the clip.