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Biological treatment of waste water

  • US 4,443,337 A
  • Filed: 02/25/1982
  • Issued: 04/17/1984
  • Est. Priority Date: 03/31/1978
  • Status: Expired due to Term
First Claim
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1. A method for biologically purifying waste water containing biodegradable substances comprising the steps of:

  • a. contacting the waste water with microorganisms in a biological fixed film type reactor under conditions sufficient to degrade the biodegradable substances and to produce a sludge which contains a mixture of bacteria, protozoa, and large organisms;

    b. separating and concentrating the sludge from the biologically treated waste water discharged from the reactor of step (a) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a static inclined screen separator;

    c. aerobically digesting the sludge discharged from the separator of step (b) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a digester; and

    d. returning substantially all of the digested sludge containing live protozoa and live organisms to the reactor of step (a) or to a line upstream thereof, whereby substantially all of the sludge is recycled.

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