The only solution to get rid of them is to make email addresses registration.
And a little bit better -> with email verification.
For me a secure solution is:
Nastyhost/VPN/TOR/PROXY-check = OK -> register-button will appear ->register with btc-address and email (ckeck if btc-address or email is in database) and captcha -> email-verification (automaticaly) -> account aprovement (manual)
Nastyhost/VPN/TOR/PROXY-check = OK -> login-button will appear -> login with btc-address or email and captcha
Also just a weekly Payout (but this case isnt good for the member i.ex. because of a missing balance - and it makes an faucet-owner able to scam very easy) so that is time to check if there happens some suspicious things in that week and can clarify with the member.