Understanding mechanism of improved-dewatering of waste activated sludge by multi-stage pressurized vertical electro-osmotic

A multi-stage pressurized vertical electro-osmotic dewatering (MS-PVEOD) were designed to break through the dewaterability limit of pressurized vertical electro-osmotic dewatering (PVEOD) process and reduce energy consumption (EC). The effects of mechanical pressure and voltage on sludge moisture content (MC) are studied. The sludge MC can be reduced to 44.6 % and 54.7 % respectively after MS-PVEOD (0–2–3.5 MPa) and PVEOD (2–2–2 MPa) process dewatering under 40 V, and the total EC of the former is 33 % lower than that of the latter. The sludge morphology, electric current, protein (PN) and polysaccharide (PS) content and fluorescence spectrum of extracellular polymeric substances (EPS) were analyzed. The PN/PS of the sludge treated by the MS-PVEOD process is 16.3 % higher than that of the PVEOD process, and 20.0 % higher than that of the raw sludge (RS). The three-dimensional fluorescence spectrum (3D-EEM) showed that the fluorescence of hydrophilic fulvic acid and humus decreased more than that of hydrophobic tryptophan protein and tyrosine protein. The present work may be helpful to understand the dewatering mechanism of MS-PVEOD and provides some useful technical guidance for the industrial application of efficient deep dewatering of sludge.