Hanoi began a project to clean a section of the capital's infamous To Lich River on May 16.

They have installed nanotechnology equipment in a 300-meter section of the severely polluted river, and it is expected to start reducing the stench within three days and decompose waste and mud at the bottom in two months.

According to one of the experts, the devices create and diffuse nano-gas streams into the surrounding water to stimulate microorganisms, which would release oxygen, decompose the mud in the riverbed and make the water cleaner.

"Japan's bio-nanotechnology fully decomposes the layer of mud at the bottom without the need for mechanical dredging, and would radically tackle the source of pollution that's been producing the To Lich River's stench."

The river had become severely contaminated in recent years. Although the two sides of the Tô Lịch River have embankments, sewage systems together with waste poured and thrown directly into the river had caused riverbed sedimentation and slow water flow.