Email in the trash is deleted when you log out - always.
OWA is the web version of Outlook which is used in the Algonquin Exchange environment. It replaces Webmail which will still remain active for students and retirees. OWA Light is a pared down version of OWA.
OWA Light Training Manual
Access
You can access OWA on campus with Internet Explorer version 6 and up. Off campus you must use VPN or Secure Portal to authenticate to the Algonquin network to use OWA. If you use any other browser you will only be able to use OWA Light. You can select OWA Light with the check box on the logon screen.

Things to know...
Shared Calendars are not supported in OWA Light.
OWA-light has a time-out which will require you to re-logon.
First time you log into OWA/OWA Light and choose your region it may bounce you back to login. First time only, after that it is fine.
OWA and OWA light seem to forget "show email photos" after session ends. Set that contact or domain as "safe" and it will show their photos as "trusted".
Macs will only work with OWA Light, not OWA.
OWA Light does not work for visual disability settings.
Check the size of email by sorting by size. Emails will be put into sized groups.
Sometimes it can not include second "to" address unless it is in contacts. Try again and be sure to use a semicolon, not a comma to separate addresses.
Trash is normally deleted from mail after logout, within 24 hrs.You must actually log out for deletion, not just shut down.
OWA light only shows one user created folder at a time