Paul-
This seems to be an odd forum to post for info on graduate work for phytoremediation. I am currently in the phyto field and have been so for a number of years, there is still much to learn to perfect this technology. Plenty of fast growing plants out there, either those commonly used for phyto or try something new. Do you have any sort of previous plant background. Even the most basic phyto documents will mention hybrid poplar trees or Indian Mustard, but these need to be researched by you if you wish to do a successful graduate project. Good luck!

Water hyacinth is the classic. Your faculty advisor surely should be able to give you a bit of a head start on this?