Engineers have completed 20 new giant treatment tanks at the Beckton sewage works extension in half the time covering an area bigger than the Olympic Stadium.

Prefabricated panels made in factories have saved 100,000 man hours and reduced costs by 15 per cent instead of having the tanks constructed on site from scratch, Thames Water announced.

“This reduces disruption and improves safety on the site,” explained Thames Waters’ Lawrence Gosden. “We’re also ending up with better pieces of kit than using traditional on-site construction methods.”

Some of the larger tanks have been made by sandwiching together the largest single pre-cast concrete panels ever used in Britain, the first time twin-wall construction has been used for tanks on this scale anywhere in the world.

The �190m extension will increase Beckton’s capacity by well over half by 2014, without the need to discharge any untreated sewage into the Thames as well as coping with the extra flows from the Lee tunnel under construction at Temple Mills in Stratford and the proposed 17-mile Thames Tideway tunnel under the riverbed between Brentford and the Isle of Dogs.