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This paper begins by discussing how the low-pressure membrane market has grown with the applications of these systemsexpanding significantly. Early low-pressure membrane applications were used historically forturbidity removal of relatively high quality source waters, but now they are used toprovide complete treatment on difficult-to-treat source waters in basically one step.As such, the solids characteristics of the reject wastewater from these systems havechanged significantly also. Based on some actual testing of membrane reject waters from a case study by the City of Lancaster, Pennsylvania, thesettling and thickening characteristics of direct feed membrane reject waters aresignificantly different than conventional water treatment sludges. Conventional gravitythickening or flotation thickening appear to realize sludge concentrations of no greaterthan 1.5% (and polymer addition does not help significantly), while mechanical (i.e. beltsor centrifuges) or enhanced thickening (i.e. DensaDeg) will be required to reliablyachieve a thickness of 2 to 3 percent. Includes tables.

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Edition: Vol. - No. Published: 03/01/2005 Number of Pages: 5File Size: 1 file , 310 KB