Thecoagulationandflocculationprocessesinconventionaldrinkingwatertreatmentgenerateaggregates which settle to form a sludge waste. This sludge can be dewatered further by thickening, centrifugation and filtration operations in order to recover water and minimise the volume of the waste stream. A range of water treatment sludges generated in the laboratory were characterised according to a phenomenological method that is valid from the dilute free-settling regime to the concentrated cake compression stages. These were compared with plant samples. Experimentalresultsshowthatrawwaternaturalorganicmatter(NOM),coagulantdoseandcoagulation pH affected both the rate and potential extent of dewatering. Similar effects were observed for both aluminiumsulfateandferricchloride.TheseresultssuggestthatincreasingdoseorpHleadstoanincrease intheproportionofrapidlyprecipitatedmaterialinthesludgeorflocs,whichformlooseraggregatesand hence exhibit inferior dewatering properties.