1) Assuming you put blast/2.2.31 into your default modules using module save, how do you undo that change?
$ module list
Currently Loaded Modules:
1) intel/16.0.1 2) cray_mpich/7.3.0 3) TACC/1.0 4) blast/2.2.31
$ module unload blast
$ module list
Currently Loaded Modules:
1) intel/16.0.1 2) cray_mpich/7.3.0 3) TACC/1.0
$ module save
Log out and log back in to see if it worked.