Method of clarifying industrial laundry wastewater using cationic dispersion polymers and anionic flocculent polymers

  • US 7,160,470 B2
  • Filed: 04/19/2004
  • Issued: 01/09/2007
  • Est. Priority Date: 04/19/2004
  • Status: Active Grant
First Claim
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1. A method of clarifying industrial laundry wastewater containing surfactants, fats, oil and grease (FOG), total petroleum hydrocarbon (TPH), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ionized metals and other contaminants, and dewatering of the sludge in the wastewater using a plate and frame sludge press, consisting essentially of the steps of:

  • (a) adding to the wastewater an effective amount of a water dispersed cationic blended coagulant of approximately 2–

    35% by solids weight of polydiallyldimethylammonium chloride (pDADMAC) and approximately 5–

    40% by solids weight of aluminum chlorohydrate (ACH);

    at between 50 ppm and 700 ppm to chemically demulsify the wastewater and produce coagulated particles having sufficient mass and cationic charge to react with an anionic flocculent to be added thereafter;

    (b) delaying any flocculent addition by at least two seconds to permit the cationic blended coagulant to substantially complete the coagulation of the particles in the wastewater in step (a);

    (c) adding to the wastewater an effective amount of a dry anionic poly(acrylamide-co-acrylate) flocculent which has been wetted to create a solution, at between 5 ppm and 50 ppm, of sufficient molecular weight and charge density to react with the cationic charged coagulated particles to form flocculated waste particles of effective size to form sludge while leaving a disposable clarified water;

    (d) separating the sludge from the clarified water;

    (e) passing the sludge to a plate and frame sludge press;

    (f) dewatering the sludge by the press, thereby forming a disposable sludge cake; and

    (g) disposing of the sludge cake and the clarified water.

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