Involvement of gypsum (CaSO4.2H2O) in water treatment sludge dewatering : a potential benefit in disposal and reuse

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Title: Involvement of gypsum (CaSO4.2H2O) in water treatment sludge dewatering : a potential benefit in disposal and reuse
Authors: Zhao, Y.Q.
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Date: Jan-2006
Abstract: This research assessed the use of gypsum (CaSO4.2H2O) as a skeleton builder for sludge dewatering since polymer conditioning of sludge affected only the rate of water release, not the extent of dewatering. The use of gypsum as a physical conditioner, in association with a polymer, could improve sludge filterability. More significantly, gypsum serves as a skeleton builder, forming a permeable and rigid lattice structure that can remain porous under high positive pressure during the compression step after the cake growth of the filtration, thereby maintaining the size of the micro-passages through which water is expressed. Experiments using a high pressure cell apparatus showed that a further decrease of two to seven percent of the equilibrium moisture content of the sludge cake was achieved, for sludge thicknesses for dewatering of 1 to 10 cm, by the addition of gypsum with 60% of the original sludge solids when compared to the single polymer conditioning. The importance of the addition of gypsum in alum sludge dewatering is not only the improvement in the extent of dewatering, but also the potential application of transforming dewatered alum sludge from ‘waste’ for landfill to useful ‘fertilizer’ or to be used as filter medium/adsorbent for wastewater treatment engineering.
Funding Details: Not applicable
Type of material: Journal Article
Publisher: Taylor & Francis
Copyright (published version): Taylor & Francis Group, LLC
Keywords: Alum sludgeConstructed wetlandsDewateringDisposalGypsumSkeleton builder
Subject LCSH: Water treatment plant residuals
Constructed wetlands
Sewage sludge--Conditioning
DOI: 10.1080/01496390600785558
Language: en
Status of Item: Peer reviewed
Appears in Collections:Centre for Water Resources Research Collection
Urban Institute Ireland Research Collection
Critical Infrastructure Group Research Collection
Civil Engineering Research Collection

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