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Dewatering of wastewater treatment wastes

  • US 4,071,447 A
  • Filed: 09/01/1976
  • Issued: 01/31/1978
  • Est. Priority Date: 04/16/1975
  • Status: Expired due to Term
First Claim
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1. A process for dewatering wastewater treatment wastes such as skimmings or sludges, comprising:

  • supplying wastewater treatment wastes of water and buoyant or precipitated impurities that had been previously coagulated during a primary treatment of the wastewater;

    entering said wastewater treatment wastes into a lower portion of a vertical column, said entering step being downwardly through a vertical zone;

    spreading said wastes at the lowermost portion of said vertical zone;

    passing a dense supply of small gas bubbles from a source lower than said lowermost portion of the vertical zone upwardly through said spread wastes;

    upwardly feeding a polymer flocculant at a location lower than said lowermost portion of the vertical zone and above the source of bubbles;

    permitting said spread wastes to contact said gas bubbles and floc to thereby form buoyant composites with the previously coagulated impurities within said wastes, confining said composites within said column, said confining step enhancing vertical movement of water and composites while limiting their horizontal movement;

    dewatering said wastes by permitting said dense supply of small gas bubbles to continue to rise within the vertical column and thereby downwardly displace all but a residual amount of water from said wastes to form an upper stratum of buoyant composites in wastes that have an impurities content significantly greater than that of said supplied wastes and a lower stratum of substantially clarified water; and

    separating said upper stratum and said lower stratum.

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