Effect of inorganic coagulant addition under hydrothermal treatment on the dewatering performance of excess sludge with various dewatering conditions

Abstract

A study for producing low moisture content sludge cake was performed by adding NaCl, CaCl 2 , Ca(OH) 2 , or FeCl 3 to excess sewage sludge under hydrothermal treatment (HT) and varying dewatering conditions from low to high pressure (0.04-12 MPa). FeCl 3 addition under HT resulted in cakes with significantly lower moisture content than HT cakes, and moreover, than raw sludge cakes, under all dewatering conditions. The addition of CaCl 2 produced similar effects to FeCl 3 addition but at weaker extents. The addition of Ca(OH) 2 produced much weaker effect than the addition of CaCl 2 under the low-pressure dewatering. However, the effects were comparable under the medium-and highpressure dewatering. The effect of NaCl addition was only prominent under the high-pressure dewatering. Comparison on the moisture content of sludge cakes with the treatments of HT, coagulant-added, and their combination showed that synergy between HT and coagulant addition in producing low moisture content sludge cake was evidenced.

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Onsite treatment of wastes in municipal waste incinerator: Co-sintering of fly ash and leachate sludge into value-added ceramic granule

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