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Environmental control for biological nutrient removal in water/wastewater treatment

  • US 5,733,456 A
  • Filed: 03/31/1997
  • Issued: 03/31/1998
  • Est. Priority Date: 03/31/1997
  • Status: Expired due to Fees
First Claim
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1. A system for biologically treating water/wastewater, comprising:

  • a first biological reactor for receiving influent water/wastewater, said first reactor being maintained in an anoxic state to effect denitrification of nitrate content delivered to it;

    a second biological reactor for receiving effluent from said first reactor, said second reactor being maintained in an aerated state to effect BOD oxidation and nitrification of ammonia content delivered to it;

    a third biological reactor downstream from said second reactor and receiving part of the discharge from the second reactor, said third reactor being maintained in an anoxic state to effect denitrification of residual nitrate delivered to it from the second reactor;

    means for recycling to said first reactor the part of the discharge from the second reactor not directed to the third reactor;

    a clarifier downstream from said third reactor for receiving and clarifying the liquid treated in said first, second and third reactors;

    an activated sludge return line for returning activated sludge from the clarifier to the first basin;

    means for sensing the oxidation potential at the inlet to and outlet from each of said reactors;

    means for adjusting the amount of liquid recycled from said second reactor to said first reactor when the oxidation potentials sensed by said sensing means satisfy predetermined criteria; and

    means for adjusting the amount of activated sludge returned through said return line when the oxidation potentials sensed by said sensing means satisfy preselected criteria.

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