This historic diagram, which had been digitally enhanced and colorized, depicted an Imhoff sewage treatment tank from a cross-sectional perspective revealing the tank's chambers. It also explained the capacity of this design to serve the needs of pupils at an average public school in Minnesota. The Imhoff tank was a chamber created to receive, and process raw sewage. At its essence, it was a two-story septic tank. It collected sewage in the upper chamber in which sedimentation took place. The solids fell down sloped inclines to a bottom chamber in which the sludge was collected and digested by bacteria.
CDC/ Minnesota Department of Health, R.N. Barr Library; Librarians Melissa Rethlefsen and Marie Jones
December 4, 2012
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