Patent ID: 6361695
Filing Date: 2002-03-26
Classification: B01D,C02F,Y02W

Abstract:
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.