Bar screen

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A bar screen is a mechanical filter used to remove large objects, such as rags and plastics, from wastewater.{{cite web|url=http://www.elmhurst.edu/~chm/vchembook/310wastewater.html |title=Waste Water Treatment Plant Elmhurst, Illinois A Virtual Tour |last=Streicher |first=Dennis |publisher=Elmhurst College |accessdate=18 February 2012 |url-status=dead|archiveurl=https://web.archive.org/web/20120329042614/http://www.elmhurst.edu/~chm/vchembook/310wastewater.html |archivedate=29 March 2012 }} It is part of the primary filtration flow and typically is the first, or preliminary, level of filtration, being installed at the influent to a wastewater treatment plant. They typically consist of a series of vertical steel bars spaced between 1 and 3 inches apart.{{cite book|last=Spellman|first=Frank R.|title=Spellman's Standard Handbook for Wastewater Operators, Volume 3|url=https://books.google.com/books?id=I1L4tV5wneAC&q=bar+screen&pg=PA85|year=2010|publisher=CRC Press|isbn=978-1439818886}}

Bar screens come in many designs. Some employ automatic cleaning mechanisms using electric motors and chains, some must be cleaned manually by means of a heavy rake. Items removed from the influent are called screenings and are collected in dumpsters and disposed of in landfills. As a bar screen collects objects, the water level will rise, and so they must be cleared regularly to prevent overflow.{{cite book|last=Ragsdale|first=Fred|title=Wastewater System Operators Manual|url=http://www.ragsdaleandassociates.com/WastewaterSystemOperatorsManual/Chapter%202%20-%20Pretreatment.pdf|publisher=Ragsdale and Associates Training Specialists, LLC|access-date=2012-02-18|archive-url=https://web.archive.org/web/20130319130344/http://www.ragsdaleandassociates.com/WastewaterSystemOperatorsManual/Chapter%202%20-%20Pretreatment.pdf|archive-date=2013-03-19|url-status=dead}}