Los Angeles-based Water Planet Inc., which develops water treatment membrane technology, said its seed investor is actor Kevin Costner, who once starred in the 1995 movie "Waterworld." The company said Costner and its founder and chief executive, Erik Hoek, actually joined forces in 2009 to develop a system aimed at cleaning up oil and gas produced water. Hoek at the time was a professor of engineering at the University of California, Los Angeles. In 2010, Hoek's system was used to clean up...