If the entire aquifer is ...

If the entire aquifer is salty, there is not much that can be done with well modifications or re-drilling.  Other (costly) desalination options have been posted.  With the size of your usage and continuous needs, I would recommend a direct distillation system.  The most direct would be electric or fueled-burner heating with condensation by preheating the inlet stream from the well..  Sustainable and cheaper designs could be done with solar heating, but the production rate may be less.  It would have to be seen if the design would supply enough fresh water for the antic-pated uses.