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Shipboard wastewater treatment system

  • US 6,361,695 B1
  • Filed: 09/30/2000
  • Issued: 03/26/2002
  • Est. Priority Date: 10/02/1999
  • Status: Expired due to Fees
First Claim
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1. A method for treating wastewater in an onboard ship treatment system having controlled suspended solids, the method comprising the steps of:

  • (a) providing wastewater in a bioreactor to oxidize organic material contained in said wastewater by adding oxygen-containing gas thereto;

    (b) operating said bioreactor to provide a mixed liquor having a solids concentration of at least 5 g/l;

    (c) continuously increasing said solids concentration in said mixed liquor in said bioreactor to not greater than 30 g/l;

    (d) when the solids concentration in said mixed liquor reaches at least 15 g/l, removing a portion of the mixed liquor from said bioreactor;

    (e) thereafter adding wastewater to said bioreactor to decrease said solids concentration of remaining mixed liquor to not less than 5 g/l;

    (f) then further operating said bioreactor to increase said solids content again;

    (g) providing a module having an array of hollow fiber membranes in a membrane container in liquid communication with said bioreactor;

    (h) sweeping said hollow fiber membranes with gas;

    (j) directing a flow of mixed liquor from said bioreactor to said container to cover said membranes to avoid substantial exposure of said hollow fibers membrane during motion of said ship;

    (k) returning concentrate and mixed liquor from said hollow fiber membrane container to said bioreactor; and

    (l) removing purified water from said mixed liquor through said hollow fiber membranes as permeate to provide treated effluent.

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