As the Project Administrator of the project-owning organization, you can manage users and organizations participating on your project.
Before removing users, note the following:
If you wish to remove an entire organization that no longer has active involvement with your project, you can change their access to archive. This effectively removes them from participation on the project.
Archived organisation’s cannot receive mail or updated documents, are not visible in the project directory and cannot be re-invited to the project (unless you or another project admin reinstates a normal access level for them).