The Red Button Design team asked the Dragons for �50,000

Red Button Design, founded by James Brown, Amanda Jones and Nicky Pang, asked the Dragons on the BBC Two show to back their business plan.

They claimed their invention, Reverse Osmosis Sanitation System (ROSS), could provide clean water to 1.2bn people.

Each Dragon has offered �10,000 for a 2% equity stake.

A deal could take place in the new year.

The trio had asked the Dragons for �50,000 for a 10% equity stake.

Ms Jones, a philosophy graduate and commercial director of Red Button Design, said: "We were thrilled with the response we received from the Dragons.

"We had gone in hoping to publicise our product and expecting a polite let down."

'Creativity and innovation'

ROSS allows users to collect water from the nearest source and sanitise it for drinking and bathing use.

It was designed in response to a challenge from the charity Water Aid.

Mr Brown, a product design student, said: "It is literally as simple as walking the unit to a water source, filling it up and pulling or pushing it back to your home.

"During that time the movement of the wheels drives the filtration process.

"By the time you've got to where you're going, you've got clean water."

Mr Brown and Mr Pang study product design on a joint course run by the University of Glasgow and the Glasgow School of Art.

Professor Seona Reid, director of The Glasgow School of Art, said: "Securing support from the Dragon's Den was an excellent end to what has been a very successful year for Red Button.

"Their Reverse Osmosis Sanitation System is an excellent example of how creativity and innovation, together with engineering, can design real solutions to real problems."