OWP will be closed from 4:00 pm on Friday, December 20, 2024, until 8:00 am on Thursday, January 2, 2025, for Winter Break.
(All times are PST.)

If exams are submitted:	Course certificates will be mailed:
By December 13th	By December 20th
After December 20th	Early January

Please note: Postmark dates will not be honored.

Water and Wastewater Terms Beginning P

A B C D E F G H I J K L M N O P Q R S T U V W Y Z

preliminary treatment

The removal of metal, rocks, rags, sand, eggshells, and similar materials that may hinder the operation of a treatment plant. Preliminary treatment is accomplished by using equipment such as bar racks or bar screens, shredders, and grit removal systems.