Tree roots in septic system---just had it cleaned----tree has been cut down but trunk is still there (small part of trunk}----how can roots be killef without interfearing with septic?

Add copper sulfate down your toilet Copper Sulfate effect on Tree (http://www.homeownershub.com/maintenance/Copper-Sulfate-effect-on-Tree-232584-.htm) and you should drill 1" holes down into the trunk and fill with more copper sulfate.