Greenwater Services, the company hired to renovate the Lincoln Memorial Reflecting Pool, says it’s using nanobubble technology in its fight against stubborn algae that keeps returning, despite past cleaning efforts. Now the landmark on Washington's National Mall is set to be drained again for repairs after algae and peeling paint appeared just weeks after a $14.7-million US renovation. »»» Subscribe to CBC News to watch more videos: http://bit.ly/1RreYWS For breaking news, video, audio and in-