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Process for the purification of waste water

  • US 4,073,722 A
  • Filed: 02/12/1976
  • Issued: 02/14/1978
  • Est. Priority Date: 09/28/1973
  • Status: Expired due to Term
First Claim
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1. In the activated sludge process wherein a first stage contaminated water containing less than about 20 ppm of hydrocarbons and less than about 20 ppm of solids is contacted with activated sludge for a period of time sufficient to biologically degrade contaminents in the water and in a second stage decontaminated water is separated from the activated sludge, a first portion of said separated sludge being recycled for recontact with the water in the first stage and a second portion of said separated sludge being treated in downstream operations, the improvement comprising:

  • introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second zone is maintained in an aerobic state and separated decontaminated water from said second stage contains at least about 3 parts of dissolved oxygen per million parts of water.

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