HOWDY
Eradication is probably not the right word to use.  Control is a better word.
I will refer you to this website for treatment options (chemical probably most widely used).  However, this is not the time of year to treat them.  The must be actively growing.

Link- http://aquaplant.tamu.edu/plant-identification/alphabetical-index/spatterdock/
There are other water lilies, so check out the website for the one you have.

Hope that helps. cd