Slow Server Response Time

I’ve been using WordPress Multisite for http://edudek.org/ for a while now. Over the past few months, people have been creating a lot of sites. The only problem is, most of them are spammy, so I have to delete them. The only problem is, Multisite doesn’t delete the table in the database for the sites I delete. So now I have over 200 tables in my database and only 30 sites. So now, my server response time is 5+ seconds. Is there any way that I can simply delete all of the old, deleted, nonexistent tables but not have to do it all manually? Thanks in advance!